650 CVT Info

CVT forum topics: http://burgmanusa.com/bkb/650+CVT (external link)
A lab analysis of the CVT: http://burgmanusa.com/forums/viewtopic.php?p=521967#p521967 (external link)

By Farqhuarforever, Colchicine, & Buffalo

All info about the 650's CVT Outline
  1. Introduction
    1. Burgman 650 CVT
  2. Components
    1. Primary Pulley
    2. Primary Pulley Stopper Bolt
    3. Primary Pulley Position Sensor
    4. Secondary Pulley
    5. CVT Belt
  3. Lifespan
  4. Reported Problems
  5. Operation
    1. Demo
    2. Auto
    3. Manual
      • Overdrive
    4. Power
    5. Engine Braking
    6. K10 and Above
  6. CVT Differences
    1. Primary Pulley Adapter Differences
    2. Primary Driven Gear
    3. ECU Differences
  7. Electrical Components
  8. Primary Pulley Stopper Bolt
  9. CVT and the Extended Warranty

Viewing the video in the link below will help visualize the explanations below.
http://www.cycleworld.com/videos/latest_videos/2013_suzuki_burgman_650_secvt_operation/#ooid=ppYXhzZDrmnNtDY68_YYQzQT1eO_909K (external link)

CVT Introduction and Overview

The CVT, or Continuously Variable Transmission (external link), is the way of the future for vehicle powertrains. By comparison with the hydraulic automatic transmissions used on most automobiles, a CVT does not actually have gears. Instead it uses a pair of pulleys that are constantly changing ratios in order to take advantage of the most efficient engine speed (or velocity) of the engine. For first time users, a CVT equipped vehicle feels and sounds strange as engine revs rise and fall within a very narrow band for the vast majority of driving / riding situations. It is only in the extremes of operation – such as high speeds or rapid acceleration - that we see engine rpm increase substantially.

A CVT is a very simple component with a minimum of moving parts, however, compared with manual or hydraulic transmissions, it is still in its relative infancy of use and only in the last decade is it starting to become widely used.

Having said that, CVTs are not a totally new technology either, they have been around for quite a number of years with the first mass availability in the late 1950s in the Dutch DAF 600 (external link) range of light vehicles, albeit without the sophisticated electronic control available in the Burgman 650. More recently Japanese manufacturers such as Honda, Nissan and Toyota have made electronic CVTs available in a broad range of vehicles, including the high power 300HP 3.5 litre V6 in the Nissan Maxima and the Hybrid Toyota Prius.

Its key features and benefits include:
  • Light weight
  • Ease of operation
  • Reduced drive train loss
  • Low construction cost
  • Improved performance and fuel consumption
  • No requirement for regular fluid replacement / replenishment (no fluids).
  • Simplified maintenance and servicing*
  • Long life*

(*)Regrettably due to the way in which Suzuki implemented the CVT in the Burgman 650 these last two items have not been fully achieved. The solution is for Suzuki to install the CVT in such a way that the CVT belt and bearings can be regularly inspected and / or replaced without engine removal and major component disassembly. Explained further below.

Burgman 650 CVT

The Burgman CVT is a unique* design amongst motorcycles /scooters. It differs from traditional scooter Variator transmissions (such as used on the other Burgman models including the 250 and 400) in that it uses computerised control for varying the width (and consequently the height/diameter at which the CVT belt rides in the pulley) of its primary pulley. The secondary pulley uses a conventional spring mechanism for varying the pulley width –at a certain rotation speed of the belt, the belt literally tries to pull itself deeper into the pulley groove thus applying pressure against the spring until the second pulley reaches its maximum width (note: there may also be centripetal force at play causing the spring to unwind and the pulley sides to separate.
(Only the Aprilia Mana  (external link)has an electronic CVT, and it has the exact same CVT as the 650 because it is licensed from Suzuki.)

When starting to roll from a stop the primary pulley is fully open and the secondary pulley fully closed. It is not clear at exactly what rotation speed the secondary pulley starts to open or reaches fully open – in addition, this is even more difficult to translate into road speed as the pulleys will vary according to road conditions such as wind (direction and strength), payload, windscreen height and gradient.

However, based on observations, the author (FF) believes that
a) at approx 2,300 rpm the secondary pulley is fully open; and
b) at 100 km/h (62 mph) and 4,000 rpm the CVT has achieved its lowest ratio in fully automatic mode.

Point a). above is determined based on the fact that the revs/speed ratio is constant at all rpm in all gears above a certain base rpm (i.e. if 3k rpm = 30 kmh (19 mph) then 6k rpm = 60 kmh (37 mph) in 3rd gear – double the revs and you double the speed) and that 2,300 rpm is the minimum speed at which one can enter second gear; and
Point b). above is determined by the fact that 100 kmh (62 mph) is also the road speed achieved in 6th (OD) at 4,000 rpm.

CVT Components

The following list of internal components is from the Suzuki official Service Manual.
Click to enlarge the photos.

Readers should refer to the diagrams above in order to identify CVT components described below.

Overview: In simple terms the CVT internals consist of a Primary (input) Pulley, Secondary (output) Pulley and a drive belt.

Both pulleys are supported at either end by sealed bearings with the exception of the output (left) end of the Secondary Pulley which runs a non-sealed bearing.

The gear mechanism for electronically opening and closing the Primary Pulley is located on its right end, whilst the Secondary Pulley has cooling fan vanes on its right side, and a spring gear mechanism on its left side for mechanically opening and closing the pulley.

Primary Pulley

As mentioned earlier, the Primary Pulley width is electronically controlled by the Burgman ECU (Electronic Engine Control Unit). The Primary Pulley accepts power from the engine and transmits it to the Secondary Pulley. The Primary Pulley Assembly is sold and described as single piece (Item 10 in the above diagram), however, for the purpose of properly describing the Primary Pulley it is necessary to break down the assembly into sub components.

The ECU is continuously monitoring a range of inputs in order to correctly set the Pulley position - including throttle opening, pollution controls, engine rpm, road speed, load on motor, current positions of the Primary and Secondary Pulleys and whether the rider has selected regular operation, power mode or manual ratio selection.

The ECU sends signals to the CVT electric motor to spin clockwise or anti-clockwise to vary the Primary Pulley width in or out. The CVT Electric motor spins very fast and turns the Primary Pulley by two plastic reduction gears (known respectively as the Actuator Counter Gear (ACG) and Actuator Idler Gear (AIG). The idler gear then turns the Primary Pulley Slide Pulley Gear (SPG), which opens and closes the Primary Pulley faces via a worm drive.

While the Primary Pulley unit is sold as a single component and is NOT intended to be disassembled, it is actually constructed from four key parts:
1) the left side pulley (or fixed) face, which is fixed to the Primary Pulley shaft and does not move sideways, it only rotates
2) the right side pulley (or sliding) face that is adjustable
3) the Primary Primary Pulley Slide Pulley Gear(SPG)
4) a hub which is locked in place in the CVT by the Primary Pulley Stopper Bolt.

The right side pulley face is moved inwards and outwards using a worm (helical) screw between its extremities of operation. At the minimum width (inner) extremity, the right side pulley face bumps up against the fixed face, whilst at its outer extremity it is limited by a stop.

Adjustment Mechanism

As explained earlier, the sliding pulley face is moved in and out by the Primary Pulley Slide Pulley Gearwhich is rotated by the Actuator Idler Gear. Now a question comes to mind, how can the idler gear move the pulley face inwards and outwards whilst the sliding pulley face is simultaneously being spun, together with the CVT belt, around at high rpm? In short, the sliding pulley face is locked to the Primary Pulley shaft to ensure it turns together with the shaft – it can only slide laterally (sideways on the shaft) – whilst the Primary Pulley Slide Pulley Gear is turned against the hub, under acceleration or deceleration (including when the ECU is optimising the CVT position for cruise mode operation) to move the pulley face in or out.

Primary Pulley Stopper Bolt (PPSB)

Now thinking further, if we have a sliding (and spinning) pulley face, and a worm gear to cause it to slide, we must also have a reference position to both know how much we have varied the pulley width, and more importantly as a fixed position for the PPG to turn against. This function is provided by the hub which is locked into place in the CVT case by the infamous CVT Stopper Bolt. (Note: I personally have not had any experience of a stopper bolt failing in any of the 3 CVTs I own – one stopper bolt had traveled 60,000 miles with minimal wear and no requirement for replacement).

A sub-article with more details on the Stopper Bolt can be viewed here.

Primary Pulley Position Sensor

The Primary Pulley Position Sensor (PPS) is by far the most common cause of the CVT failing to operate correctly.

The purpose of the PPS is to provide information to the ECU on exactly how far the Primary Pulley face has moved inward or outward. It is not simply a binary switch –the PPS contains a large number of chips and provides constantly variable feedback to the ECU in order that the ECU can send the correct signals to the CVT motor. Externally the PPS uses a sliding rod which is spring loaded so as to constantly push against the outer face of the SPG. A rubber bellow surrounds the rod with the intent of preventing water entry. Internally the rod then moves a pair of sliding contacts across a set of trace wires on a circuit board. Dependent on where the sliding contacts are resting on the circuit board, a different signal will be sent to the ECU.

Side on external view of a good PPS

Damaged PPS with bellows removed showing slider rod spring

Slider rod removed from PPS – note sliding contacts

PPS circuit board removed (note that the cracks were caused during removal and were not a failure condition)

Symptoms of PPPS Failure

Of all the inputs to the ECU, the PPS is by far the most important for CVT control. As such, when a PPS goes awry, or starts to fail it can send incorrect signals to the ECU which in a best case scenario will limit the CVT’s range of operations, or cause the CVT to operate erratically. In a worst case scenario it can actually cause damage to the internal components of the CVT.

The author (FF) of this article has experienced all 3 scenarios.
  1. Erratic running. The CVT was twice flooded with water causing the PPS to internally short out and send signals to the ECU the opposite of what was actually occurring. The Burgman would run erratically, constantly changing the CVT ratios up and down in regular mode of operation and switching between gears / locking gears out in Manual mode. A new PPS cured the problem completely. The root cause of this problem was water entry to the CVT and PPS.
  2. CVT damage. In attempting to diagnose the Erratic Running problem above, the damaged PPS was swapped out into a second Burgman. The incorrect signals from the PPS caused the CVT motor in the second Burgman to continue to try and close the Primary Pulley even when it was already closed. As a result the plastic Actuator gears were torn apart and required CVT removal and disassembly in order to replace. The root cause of this problem was the author putting a damaged PPS into a good CVT.
  3. Limited range of Operations. On a long distance ride the author noticed that as he slowed from highway speeds and then tried to accelerate again the CVT would hold the lower ratio and the bike would require higher revs to achieve the same speed. In addition, Manual and Power modes were unavailable. The PPS was replaced and the problem resolved with no longer term effects to the bike. Upon subsequent testing and examination of the PPS it was discovered that at maximum extension (which is normal for high speed cruising) the PPS trace wires were eroded from over use. The root cause of this problem was wear and tear on the PPS – it had simply exceeded its service life at around 85,000km (52,800 miles).

It should be noted that in some instances the PPS can still be the problem without displaying the FI light and a C code. In addition, the Burgman repair manual does not accurately describe all C codes. The author (FF) strongly recommends that the PPS be the first item to be swapped when attempting to diagnose erratic CVT behaviour.

Secondary Pulley

The Secondary Pulley uses a conventional spring mechanism for varying the pulley width. The right side (or inner) pulley face is locked to the Secondary Pulley shaft whilst the left side (or outer) face is able to slide outwards against spring pressure. The Secondary Pulley accepts power from the Primary Pulley and transmits it to the "Transmission".

The secondary pulley has a set of vanes attached to its right most side. These vanes draw air into the CVT through the filter and provide cooling to the CVT under all riding conditions. There is an exit at the top of the CVT case for the air to escape, resulting in the constant circulation of ambient temperature air whilst the motor is running.

The ratios for the Secondary Pulley are the reverse of the primary Pulley – the highest ratio is available at its narrowest width (or highest belt position between the pulley faces). By comparison, at a stop, the ECU positions the Primary Pulley at its highest ratio (maximum pulley width).

In summary, maximum acceleration (and lowest speed) is available using a combination of the lowest Primary Pulley Position and highest Secondary Pulley Position, whilst maximum (theoretical) speed is available using the reverse.

Secondary Pulley Position Sensor

By comparison with the PPS, the Secondary Pulley Position sensor is a very simple static item (no moving parts) that signals whether or not the Secondary Pulley has achieved maximum extension.

The Secondary Pulley Position sensor rarely – if ever – fails. However, should it fail the CVT requires removal from the motor in order to replace it.

CVT Belt

The CVT belt is essentially two belts – not one. It is made up of a pair of Kevlar belts joined by a large number (hundreds) of metal links pressed tightly up against each other.

In order to provide grip between the belt and the pulleys, the Secondary Pulley is offset from the Primary Pulley. As a result the CVT Belt runs on a slant– not straight between the pulleys. It is the author’s belief that it is this feature that allows the belt to not only grip the pulleys, but also provides the means by which the belt can climb and descend the pulley faces- otherwise it would simply jam when the ECU sends the signal to the CVT motor to close the Primary Pulley.

Power Transmission

From the crankshaft the motor’s power is transmitted to the rear wheel as follows:

  1. Gear on end of crankshaft meshes with external teeth on PDG.
  2. External to the CVT PDG internal splines mesh with PPA (K3/K4) or directly to CVT Primary Pulley (K5+)
  3. Internal to the CVT the Primary Pulley turns the CVT belt which then turns the CVT Secondary Pulley – for explanation of internals of CVT see CVT Internals Description.
  4. External to the CVT, the Secondary Pulley splines mesh to the internal splines of the Secondary Pulley Fixed Adaptor (SPFA).
  5. The external gear teeth of the SPA then meshes with the external teeth of the Clutch Hub
  6. The Clutch Hub engages via the centrifugally operated clutch (complete engagement at approx. 2,000 rpm) to transmit power to the Clutch Shaft.
  7. The Clutch Shaft transmits power to the gear reducer’s Counter Shaft (what Suzuki calls the “Transmission”).
  8. The Driveshaft of the transmission then engages with the Final Driven Gear which is located on the Shaft Drive inner splines. From there the Shaft Drive outer splines connect with the Final Drive Unit and finally to the rear wheel.


The CVT is estimated (by the author) to have a service life of between 80,000 and 160,000 km (50,000 to 100,000 miles), however, like most components of any mechanical device the actual service is highly dependent on the type of usage the rider puts it to. As an example, a rider who travels long distances in freeway conditions with a minimum of braking / acceleration, and stop /start traffic, is likely to have their CVT belt last longer. It should be strongly noted that a CVT belt breaking on its own without being directly affected by another failed component is very rare. Most broken belts are associated with seized bearings of the CVT. When the CVT belt does snap it will likely result in major scoring of the pulley faces as the now loose belt links jam in the pulley faces.

At the other end of the spectrum, a rider who uses their Burgman for inner city commuting, or aggressive sports style riding with fast acceleration and hard braking is likely to receive shorter service life. .

The CVT belt on my (FF) K3 Burgman (built in December 2002) snapped at 95,000km (60,000 miles) from sheer wear and tear.

Belt failure early in the belt life is highly unlikely to be a result of belt wear but by component failure in the Primary Pulley, specifically the input side (left side) bearing which has been known to seize.

Reported Problems

Apart from the previously mentioned PDG / PPA spline failure, Bearing, and PPS failures there are a number of other known problems.

1) Belt Breakage
The belt will snap either as a result of bearing failure or simply at the end of its service life (as mentioned earlier between 80,000 and 160,000km)

2) Primary Shaft Adapter
3) Pulley Position Sensor
4) Seized Pulley Bearings
5) Pulley Revolution Sensor Failure
6) Primary Pulley Stopper Bolt
There have been reports of failure, however, the bolt in my own Burgman had minimal wear after 96,000km

7) Varmit Damage
Rodents in particular have been known to climb into a parked or winterized 650, via the large CVT exhaust, and either build nests that interfere the CVT operation, or get caught up in the moving parts. If you do not have a screen over the CVT exhaust, it is highly recommended that you plug the exhaust with a leader trailing to outside of the tupperware to remind you of it's need for removal before starting up again.



http://www.pirmil.info/scoot/ssiburg/650info_suzuki-1_cvtdemo.shtml (external link)

There are 3 modes in which a rider can utilize the CVT.


This is the mode the 650 is in when it is first turned on. It balances between fuel economy that scooters are expected to have, and the power the 650 is capable of.

Manual Mode

Manual mode allows the rider to switch the CVT primary pulley position manually between a fixed number of ratios, using a pair of up/down buttons on the left handlebar switch cluster. For K3/K4 there were 5 fixed ratios, and a 6th (Overdrive) was added for the K5 and above models. Note that Manual Mode does not provide full manual control – the ECU will not allow change up below certain speeds and will automatically change down below certain speeds. If the motorcycle is brought to a halt the CVT will automatically start off in 1st gear. Like a regular manual gearbox the CVT will not change up to the next gear unless specifically selected by the rider.

In manual mode the gear ranges available are as follows:
RatioMinimum Change Up PointAutomatic Change Down PointMaximum Speed in Ratio
1N/AN/A57 kmh
222 kmh17 kmh85 kmh
330 kmh24 kmh120kmh
440 kmh32kmhTBD
550 kmhTBD200 kmh (theoretical)
659 kmhTBD212 kmh (theoretical)

RatioMinimum Change UpPoint Automatic Change Down PointMaximum Speed in Ratio.
1N/AN/A35 mph
214 mph11 mph53 mph
319 mph15 mph76 mph
425 mph20mphTBD
532 mphTBD124 mph (theoretical)
637 mphTBD132 mph (theoretical)

Note 1: speeds stated above are according to the speedometer which reads 10% high.
Note 2: at ~13 kmh (8 mph) the clutch will automatically release. With the bike rolling (e.g. whilst coasting downhill with minimal throttle input) the clutch will not re-engage until 24 kmh (15 mph).

Power mode

Power mode is an electronically selected option (push button) that holds the CVT ratio lower with an approximately 1,200 rpm higher than regular RPM (author’s note: I believe this to correspond with the engine’s power peak whilst the Auto mode corresponds with the engine’s torque peak). The purpose of Power Mode is to improve acceleration performance, it also has a side benefit of providing stronger engine braking when decelerating.

Engine Braking

By Colchicine

Engine braking (external link) is a prominent feature of the 650. Although most people find it to be comparable to or less than some manual transmission motorcycles, it is a feature that bothers a lot of users while some others actually favor it. It is ideal riding in the twisties.

Here's an explanation for why there is strong engine braking in the 650.
Anytime you let off the throttle, the computer is setting the CVT up to be ready for the next throttle input. If the computer kept the same gear ratio as when the throttle was rolled off (therefore, less engine braking), there are going to be too many instances where the CVT is going to be in too high of a gear because the bike has slowed down, resulting in a lack of power or worse, lugging. The computer is monitoring the throttle position and speedometer signal and adjusting the pulleys to a gear ratio that maximizes available power when the throttle (or rider) calls for it. This also eliminates the possibility of lugging the engine.

http://burgmanusa.com/forums/viewtopic.php?p=413446#p413446 (external link)
http://www.burgmanusa.com/forums/viewtopic.php?p=393946#p393946 (external link)
http://burgmanusa.com/forums/viewtopic.php?p=413432#p413432 (external link)
http://burgmanusa.com/forums/viewtopic.php?p=412002#p412002 (external link)

K10 and Above

The 2010 and later Burgman models also feature two additional features.

Firstly, an increase in the number of manual mode ratios from 6 to 7; and secondly, a new feature whereby manually selected gears will automatically change up to the next ratio at redline (instead of the engine bouncing off the rev limiter).

CVT differences

Between the K3/K4 (2003 / 2004) and K5+ (2005+)

In late 2004 Suzuki introduced the K5 as 2005 model upgrade. A number of cosmetic and technical changes occurred (See 650 Year Differences) and the specific changes affecting the CVT are discussed below.

Internally all model Burgman CVTs are identical, the only difference between models being the change to the Primary Pulley Adaptor (PPA), which is attached externally to the primary shaft via splines. The PPA then has a set of external splines which mesh into the Primary Driven Gear (PDG) - internal to the motor and NOT removable without splitting the crankcases. In addition to the new shape PPA Suzuki also changed the internal diameter of the PDG.

The purpose of these changes was to improve the service life of the motor/CVT and reduce the ‘dieseling’ noise at idle (See Dieseling), which most K3 / K4s start to display early in their life and which becomes progressively noisier over the life of the motor. The dieseling has nothing to do with a diesel effect – it is simply named that way because it sounds very much like the combustion rattle of a diesel motor at idle.

The dieseling noise is actually caused by play in the meshing of the PPA and PDG splines and eventually results in jerkiness/slop when quickly opening and closing the throttle – over time, the spline teeth can be completely worn away resulting in the PDG being unable to transmit power to the PPA (this has happened to a number of forum members including “Burgermann”). Dependent on which component has lost its splines (PDG, PPA or both) the feasibility of repair and replacement can be determined. However, in most instances the simple replacement of the complete motor / CVT / drive train with a used item is probably the most cost effective repair, especially if the owner feels competent enough to perform the task without needing to resort to using Suzuki service personnel.

Primary Pulley Adapter Differences


It is possible to detach the CVT from the motor without first removing the PPA. Compared with the K5+ PPA it has fewer, larger external splines. It should be firmly attached to the Primary shaft before assembly of the CVT to the motor (as it requires massive torque to tighten fully). The PDG also has a larger internal diameter with fewer splines.


The newer model requires removal of the PPA in order that the CVT can be separated from the motor. It has a larger number of external splines and cannot be attached to the CVT Primary shaft until the CVT is fully bolted up the motor. It does not connect directly to the CVT but instead connects only to the PDG outer splines (see PDG below).

It is NOT possible to replace the K3/K4 PPA with the K5+ PPA without also replacing the PDG. As PDG replacement requires complete disassembly of the motor it is not usually a cost effective repair.

Primary Driven Gear

The Primary Driven Gear (PDG) has two sets of splines – an inner (right side) and an outer set (left side).

On the K3/K4 the outer set is unused (if you had a suitable tool it could actually be used to lock the PDG in order to allow the PPA to be removed) and the PPA slides partially into the inner splines (Note: it does not fit fully) – it is the bolts attaching the CVT to the motor and the bolt attaching the PPA to the Primary Pulley spline that hold it in place and prevent lateral (sideways) movement. However, the PDG does have a small amount of lateral movement.

Insert images of PPG here

On the K5 and above the big difference in the PDG is that it has a smaller internal diameter and the Primary Pulley splines fit directly within the PDG inner splines. In addition, the new design PPA fits into the PDG outer splines and is locked into place by a bolt. This achieves two things, first it further reduces lateral movement of the PDG; and second - by providing an additional attachment point - it reduces the rocking movement of the Primary Pulley Spline in the PDG. However, and importantly, it should be noted that the K5+ PPA is not intended to transfer power to the CVT, this is because it is not directly connected to the CVT – it is only the tightness of the PPA bolt that keeps it connected to the CVT, and without the spline connection between the Primary Pulley and the PDG it would simply slip and the PPA bolt would undo.

ECU Differences

K3/4 to K5+
Interestingly, together with the change to the PPA and PDG from the K5 forwards, Suzuki also made major changes to the ECU which have dramatically altered the personality of the Burgman 650.

The K3/K4 actually uses a separate ECU for the CVT and the rest of the Engine operations. In the K5+ these have been integrated into a single unit – one benefit of this is that it is no longer possible to receive a C50 – ECU to CVT Controller signal failure - error code.

In addition, a sixth - manually selected - overdrive (OD) gear has been added. Selecting sixth (at any speed above 60 kmh (37mph)) allows the user to significantly reduce engine RPM (and fuel consumption) but with a consequent decrease in flexibility and pulling power. Note: it should be noted that OD does NOT provide a lower ratio than Auto mode will achieve on any model Burgman (whether K3/K4 or K5+, however, it will allow the rider to lock-in that ratio instead of allowing the ECU to decide what it believes to be the correct (possibly higher ratio) gear.

It is in regular running that the biggest difference is noted though. The K3/K4 will typically sit at around 3-3,200 RPM in Auto mode when running below 80 kmh (50 mph). By comparison the K5+ runs 7-800 rpm higher – the engine feels a lot less relaxed and the on/off throttle lurch is considerably exaggerated.

In addition, when the throttle is opened a moderate amount the K3/K4 will accelerate with minimal increase in engine rpm – the motor feels torquey and relaxed. In the same scenario, the K5+ ‘kicks down the CVT’ and dramatically increases it revs to accelerate away.

The K5+ feels like a frisky pony – agile, nimble and willing to kick up its heels – whilst the K3/K4 feels ponderous, but more relaxed and satisfying to ride.

Electrical Components

By Colchicine

In the 2003 and 2004 models, there are actually two separate computers in the 650, one is the ECM that controls the fuel injection and most aspects of the bike. The ECM also receives input from the CVT control unit via a serial communication harness of wires. In models 2005+, these two computers have been combined.

The CVT computer keeps track of the actual CVT ratio and compares it to the target CVT ratio. The Speed Sensor and Throttle Position Sensor are used to determine the target CVT ratio. The Crankshaft Position Sensor (engine RPM), the CVT Pulley Position Sensor, and the CVT Secondary Pulley Revolution Sensor is used to determine the actual CVT ratio. The CVT computer then makes appropriate adjustments to the CVT Motor that controls the gear ratios the primary pulley assembly is adjusted by the CVT Motor or as the secondary pulley is completely passive and is adjusted by spring tension and centrifugal force.

There is a failsafe mode built into the CVT to prevent damage in case some of the sensors malfunction. The sensors that will produce a failsafe mode includes the Pulley Position Sensor, Speed Sensor, Secondary Pulley Revolution Sensor, Engine Revolution Signal, and the Center Stand Switch. During failsafe mode, shifting to manual mode may be inhibited and the gear ratio is fixed to an equivalent of the first gear as all other shifting his inhibited. Basically, if the CVT control unit cannot read all parameters of the CVT's operation it will lock the primary pulley in place, otherwise significant damage to the CVT may occur.

There are a total of seven malfunctioning codes that can relate to the CVT.

C50 CVT serial communication (Not used on 05+ models)
C51 CVT motor
C52 CVT pulley position sensor
C53 CVT speed sensor
C54 CVT secondary pulley position sensor
C55 CVT engine revolution signal
C56 CVT throttle position signal
C57 not used
C58 CVT reduction ratio disagreement

Primary Pulley Stopper Bolt

By Colchicine

Description of Part

Suzuki part name: Primary Pulley Stopper Bolt
The Primary Pulley Stopper Bolt (referred to as the “Stopper Bolt” in this article) is a unique and proprietary bolt and one that functions like a set screw. The unthreaded end of the shaft is 0.6 cm (0.23 inch)long and has a diameter slightly smaller than the threads. The end of the bolt fits into a slot in the bottom of the Primary Pulley Cover. The entire bolt is 2 cm long from below the head of the bolt, and the space in which it fits is 2.1 cm.

Affected Component / System

The Stopper Bolt is exclusively a component of the Continuously Variable Transmission (CVT) system. In the event of a failure of the Stopper Bolt, damage has been confined solely to the CVT.

Function of Part

The Burgman 650 CVT is electronically controlled with the bike's computer, the "ECM". The Primary Pulley receives power directly from the engine, and it is this pulley that is adjusted electronically to control the gear ratios of the transmission. The Secondary Pulley is adjusted passively with spring tension and centrifugal force. In order to adjust the Primary Pulley's position, one side of the pulley face is moved in and out along a worm gear (like the threads on a screw) attached to the Primary Pulley Cover. In order to anchor the side of the worm gear that does not spin, the Stopper Bolt is used to keep the entire assembly from rotating with the engine input. Without the Stopper Bolt, there would be no anchor in which to adjust the Primary Pulley.

Example: If the motor and fan blades for a ceiling fan were modified to hang freely without any point of contact, supplying electricity to the motor would immediately make the motor spin on itself without spinning the fan blades. It is not until the motor is anchored to the ceiling when it will remain stationary and spend the fan blades as intended. The bolt provides that anchor and allows the CVT to adjust the gear ratios.

Other's explanations from the forum:
The stopper bolt is a simple device that anchors the end of the Primary Pulley so that a "screw shaft" can adjust the distance between the two pulley surfaces (see There is this stopper bolt, it's a simple device that anchors the end of the Primary Pulley so that a "screw shaft" can adjust the distance between the two pulley surfaces (see pages 5-19 to 5-20 in the service manual).s 5-19 to 5-20 in the service manual).

All that bolt does is keep the back plate on the adjuster from moving when the stepper motor adjusts the Primary Pulley face in and out. Without it the adjuster would just spin on the shaft without moving the pulley face.

The function of the stopper bolt is to hold the position of the Primary Pulley back plate when the ECM turns the worm gear to adjust the ratio of the pulley. Without it the transmission could not shift gears.

Perceived Problem / Cause of Failures

Damage occurs to the CVT when the primary puller stopper bolt fails to anchor the Primary Pulley and the adjustment components of the Primary Pulley are allowed to spin along with the engine speed. Apparently, the area the bolt mates with the Primary Pulley Cover is shallow. Only 2-3 mm of the bolt actually contacts the Primary Pulley. Also, there is some amount of space, about 1 mm, between the bolt and the Primary Pulley. When the Primary Pulley is being used to adjust the gear ratios, the minute amount of play results in the Cover slapping against the bolt. Over time, this slapping action will wear off the end of the bolt. Because only a few millimeters of the bolt is being engaged, enough wear on the bolt can occur to wear a groove in the bolt, allowing the Primary Pulley to spin and no longer be anchored. It has been theorized on the forums that machining the bottom of the head of the bolt to remove 1 mm of material will better engage with the Primary Pulley and reduce the chances of the Stopper Bolt failing.

Actions to minimize wear on the Stopper Bolt:
  • Smooth throttle control
  • Using Manual mode, especially when on interstates with high sustained speeds

Mileage at Failure

At this point, we have no common thread that links failures, or a mileage at which a failure is likeliest to happen. City type driving doesn’t appear to wear on the bolt any more than highway miles. Failures have occurred at as few as 10,000(?) miles and as much as 30,000(?) miles. Since 650 owners have only recently been made aware of this problem, it may take more time and more observations to find a common thread among the failures.

Consequence of Doing Nothing.

By not replacing the bolt, the wear on the end of the shaft may accumulate to the point that it can no longer anchor the Primary Pulley Cover. If the engine is operated after the bolt's failure, it is theorized that it creates more damage by allowing the Primary Pulley Cover to spin in proportion to the engine's RPM, an action it was not designed for. Since the Primary Pulley would only be anchored on one end while it is spinning, the bearings holding the Primary Pulley in place would be subjected to loads that are not axial, or inline with the rotation of the input shaft. With a potential for the Primary Pulley to wobble, it can very easily lead to a failure of the bearings of the Primary Pulley assembly. When bearings fail, they tend to seize, which brings the entire drivetrain to a stop, and can damage any number of other components in the CVT.

Since we have no record of a CVT belt breaking without another component of the CVT failing first, it is likely that most belts that break are the result of bearings seizing. While at speed, a bearing failure of one of the two pulleys in the CVT wouldn’t prevent the other pulley from continuing from spinning. If one pulley continues to spin and the other is seized, the belt would be subjected to heat from friction. The epoxy and rubber components of the belt would break down an delaminate or deteriorate to the point that the CVT belt would break or shred.

Benefits of Inspecting / Replacing the Bolt

No Tupperware (body panels) need to be removed. Only some preventative procedures to ensure the Primary Pulley Cover does not move need to be done during the procedure. A replacement costs less than $10 and completely eliminates the possibility of an imminent failure to anchor the Primary Pulley.

Cost and Time to Inspect / Replace the Bolt

The bolt costs around $8 without dealer markup or shipping charges. Inspecting or replacing the bolt can take less than 1 minute to accomplish with the benefit of experience. For a first timer, it shouldn’t take more than 20 minutes to gather the necessary tools, remove and replace the bolt, and put back the tools.

What Suzuki is doing About it

It is apparent that Suzuki is aware of this problem, as several failures have resulted in Suzuki fixing CVTs while under warranty. Suzuki has changed the part number of the bolt, indicating they somehow improved bolt. It is listed as part # 21748-10G00 and is SUPERSEDED by part # 21748-10G10. It is not known exactly what has changed with the bolt, other than the superficial change in color (from a brass color to a silver color). It is assumed that the metal of the bolt is now harder. It also thought that the Stopper Bolt has been changed to the newer part in all 2009+ models. It appears that this improved bolt wears much better (less) than the previous style bolt and is doing a sufficient job.

In the US, we are not aware of dealerships being issued a Service Bulletin. However, in the UK we have the following info:

http://burgmanusa.com/forums/viewtopic.php?p=423810#p423810 (external link)
Suzuki have issued a new service bulletin regarding the bolt in question, I believe the bolt now has to be inspected for wear every 4.5k (Kms or Miles-unknown) service. If worn it has to be replaced during the service. I'm not sure if this has rolled out globally but it does show that Suzuki (GB at least) have acknowledged the issue. Obviously a lowly parts assistant such as myself cannot speak for Suzuki and I'm sure that regular inspection of the bolt should be regarded as no more intimidating than simply checking if you need new spark plugs etc. just thought I'd let you know that feedback from dealer and customers does appear to reach Suzuki and that they do look into such claims.

Sources for the Bolt

Since this problem was made known, there has been shortage of the bolt due to owners wanting to replace their bolt. The bolt is proprietary and there is no non-OEM source. A list of online vendors are here:
http://burgmanusa.com/bkb/650+OEM+Parts+Fiche (external link)

Thanks to Buffalo and boxermania26 for their forum contributions that aided in the creation of this article.

Inspection / Replacement of Stopper Bolt

This is the procedure for inspecting your primary pulley stopper bolt.
  1. Make sure the exhaust is cool since you'll be working right beside it.
  2. Fully apply the Brake Lock. Remove the key from the ignition. Turning the key while the bolt is out may reposition the primary pulley, requiring a full disassembly in order to replace the bolt.
  3. The bolt is entirely visible with the bike on the side stand and with the lower leg shield installed. No tupperware needs to be removed. There is a convenient cut out in the bottom of the lower leg shield that allows access to the bolt.
  4. A knee pad and headlight / drop light will aid in the visualization.
  5. Remove the bolt with a 14mm socket. A few taps on the ratchet with a rubber mallet will do.
  6. Reinstall or install a new bolt. Clean the housing of the CVT where the bolt head sits, just as you would an oil drain plug.
  7. Torque to 26 ft-lbs.
  8. Confirm that the bolt is fully installed and seated. If the bolt gets tight and the bolt head is not resting against the CVT housing, the bolt is not sitting in the "cutaway" of the "primary pulley cover".
  9. Post pictures and your mileage of the bolt on the BUSA forums!

An instructional video by LeDude is also available.
http://www.youtube.com/watch?v=0rZE-bacaYw&feature=player_embedded (external link)

Author’s Background.
FarquarForever (Garry) owns both a K3 and K8 Burgman, and has disassembled 3 CVTs, and removed / replaced / repaired 4 motor / CVT assemblies. The notes provided above are based on the writer’s direct experience and are not intended to be a definitive description of the CVT operation as initially envisaged by Suzuki designers and engineers.

Contributors to this page: Colchicine and Redbeard .
Page last modified on Wednesday 13 of November, 2013 15:04:17 CST by Colchicine.

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