Valve adjustment

[Waldo]

Who has actually had Valves out of spec and had to have it adjusted and at how many miles?

[LeDude]

FYI -- Extract from this thread valve adjustment

Re: Valve Adjustment
by -terry on Fri May 23, 2008 19:02 19

I make this same reply every time the topic comes up. My valves ('06 650) were checked at 15,000. Three were out of spec. Just FYI. Don't leave it unchecked forever.
White AN650K6, the "Devil's Snowflake"
Purchased new (8/1/06)

Other than this one I think I recall reading another instance about someone's valves being out of spec, not that many actual instances, of course those that have had it done by dealers probably just take their words for it.

[Waldo]

I guess..
What are symtoms of valves being out of spec?

[djb383]

I would doubt seriously if there are any symptoms that a valve is going out of spec.....that's why the valve lash is checked on a mechanical valve train.....to see if the valve lash is decreasing. If it decreases to zero, that's when valve burning/valve seat damage occurs and cylinder compression decreases causing poor performance. As long as there is some valve lash, the valve will continue to seal. Again, checking the lash/valve clearance spec is the only way to tell for sure. Hydraulic valve trains self-adjust, mechanical valve trains don't, therefore they need to be checked to see if adjustment is necessary. There are numerous articles on the net discussing engine valves.

http://autos.yahoo.com/maintain/repairq ... 053_1.html

[excaliber]

Primary symptom would be a loss of power, if the valve is really tight, it will only idle or turn up to a few thousand rpm then either die outright or chug along. It's primarily the EXHAUST valves that are going to get to tight, they run much hotter than the intake valves. With the valve not being able to fully 'seat/seal' exhaust remains inside the combustion chamber greatly diluting the incoming fresh air/fuel mixture, thus reducing horse power. More tight, more reduction of power, mpg suffers as well. Think of it like slowly being choked to death... Based on MY experience with small engines/motorcycle engines a burned valve or serious damage to the head/valve is unlikely. The motor simply slowly looses power over time until it has lost virtually all it's power if the valve gets tight enough, adjust back to specs and your 'good to go'.

MULTI cylinder engines are more problematic than a single piston setup. Like a V6 or V8 with ONE tight valve, you may not sense the loss of power in time to stop engine damage, because the other cylinders provide 'enough' power to keep going. Thus you drive on and ruin/burn the one bad valve. Motorcycle engines (two to four cylinder) are small enough you DO sense the power loss early on and get it fixed before damage occurs.

Slightly tight valves or valves adjusted to the 'tight' side of the specs make MORE horse power than loose valves. Thats one reason you sometimes hear a guy say, "Man it was running great, never better, just before it blew up." The valves may have gone from 'tight and right' to 'to tight and bad'! Or the piston crankshaft clearance was nice and 'loose', like just before it let it go!

[djb383]

.......how much HP increase on the tight side? A fraction maybe? There's a big difference between adjusting valves on an old school solid lifter push rod car motor and the B650. I could run all 16 valves on my son's '68 Buick 455, button it up and make a 11.90 pass in less time than it takes to remove one piece if tupperware from the B650. Setting the valves tight is not the way to go on the Burgman.

[excaliber]

I totally agree with NOT setting the valves on a Burgie on the tight side! It is a fraction, if that, in gained horse power. My point was as the valves tighten up you may experience an engine that runs 'better than ever', which would make it seem like 'all is well'. You can trust a 'loss of power' as a symptom, but not necessarily a 'run's great' scenario.

When I was racing Formul Ford's it was a common trick to set the valves on the tight side and every other little trick we could think of to get that last itty bitty piece of horse power out of it.