This might seem obvious to some but I think I finally got a good feel for the impacts of poorly adjusted valves - in general.

Penalties for bad adjustment:

1) Too tight = they dont close all they way and hot exhaust gasses can escape past the valve and "burn a valve".
2) Too loose = can beat up the valve seat due to the increased velocity of the valve slapping shut.
3) Loose is generally less damaging than tight but always keep them properly adjusted.

Please correct me if I've got it wrong but I think it's accurate.

 

How would you know if you have poorly adjusted valves as far as riding characteristics?

 

Loose will introduce a clatter or tick sound. Tight - not sure what the outward symptoms would be ? I think the best thing to do is to check the valve adjustment regularly.

In the case of my Raptor, it seems that every time I've checked, the exhasut valves are fine but the intakes tightens up. Frequent checks seem pretty important.

 

Another result of too little valve tolerance that many don't realize is that if the intakes are too tight, the compression stroke will blow combution back through the intake which could damage your carbs and like some raptors, blow them off the intake boots. Many people who have this problem however don't seem to take into account that if the bike is backfiring, there is an engine problem and will instead try buying after market boots or carbs when the problem is simple maintenance.

~Matt

P.S. Water cooled engines tend to have their valves tighten over time as Fisher's did.
Air cooled engines tend to have their valves loosen over time.
Both can cause problems so check your valves from time to time. It's time well spent.

 

Dog06,

Excellent point on the backfire issure/carb boots. I'll bet that accounts for the majority of probs in this area for the Raptors since the intake valves seem to consistantly tighten over time. I think that's the first time I've heard anybody link the problem to valves. Makes good sense to me !!

 

I just learned that lesson the hard way although I set mine a little too tight and one (or more?) of the intake valves wasn't sealing properly as the RPMs climbed. Added less than .001" and things straightened out again.

 

You could also be loosing power in different areas if they are not adjusted properly. Mine were too tight before and I could actually tell just by riding the bike because it was loosing top end. I adjusted the valves like they were suppose to be and it started running like it was suppose to all the way around. I could tell an immediate change in performance by the way the bike was pulling after they were adjusted correctly. Slim (ADJUST THEM FREQUENTLY)

 

When your valves get too tight it'll be real hard to start (no compression).

 

To follow up on what Shady Rascal said it wont idle right either. How often do you guys adjust yours. Mine are being done for the first time today.

 

Whenever the plastic and tank happen to be off and/or about every 3 oil changes....dont know if this is a good schedule but it seems to be OK....