Reason for Valve Adjustment

[E400X]

I just got the DIY Valve Adjustment Guide from this site and want to attempt this myself this weekend, but I have a few questions first.
1) What is the reason for a valve adjustment so often on these bikes?
2) What part of the Valve Train are you actually adjusting?
3) What happens to the bike if the adjustment is either to loose or to tight?
Thanks for the help, I like to know how things work and get some knowledge of it before i start taking things apart.

[shelbygt350]

Me too, I mean I don't want to go adjusting anything that does not need to be fixed, My 2002 400 runs FLAWLESS!! no pings, rattles, squeaks or shimmy's. I run a constant 92 octane with honda 4 stroke oil and never really get on the machine. This past weekend was the 5th or 6th time I've gotten it into 5th gear:)

1. if its too tight i can burn up a valve, too loose you loose power
2rockers and valves
3too tight it can burn up a valve too loose you loose power

[E400X]

Thanks blazin

Can you explain to me how a valve can get burnt up when it is too tight and also how the bike loses power when it is too loose? Thanks again for the help.

[dariusld]

The valve gets burnt up when its to tight because the valve isn't seating all the way. When the valve sits, it transfers its heat to the head. So if it never sits all the way, it doesn't cool. That's why, when adjusting your valves, it's better to be a little loose than tight. The most important part of an engine is breathing. If the valves are not opening wide enough your engine isn't getting enough air. The less air your motor is getting, the less power it makes.

Originally posted by dariusld
The valve gets burnt up when its to tight because the valve isn't seating all the way. When the valve sits, it transfers its heat to the head. So if it never sits all the way, it doesn't cool. That's why, when adjusting your valves, it's better to be a little loose than tight. The most important part of an engine is breathing. If the valves are not opening wide enough your engine isn't getting enough air. The less air your motor is getting, the less power it makes.

yep u beat me too it

[E400X]

Thanks dariusld

Am I right to assume that valve seating means it is completely closed. I am confused on how the the valve cools when it is seated. Can you explain. Sorry for these dumb questions I just like to learn how everything works and this is stuff you can't get out off a manual. Thanks for all the help.

[dariusld]

Yes the valve is closed when seated. The valve is hotter than the cylinder head. So when the valve seats, it transfers its heat to the cooler head. This is not a dumb question because you wouldn't think that it would make that much of a difference, but it does.

[eddie440]

first of all i say if its not broke dont fix it! if your valves are not making any noise and you have good power leave them alone. when you take it to the dealer for a valve adj. and its nice and quiet you can bet there not going to mess with them even if they say they did.i recomend you check them and if their within 1 or2 thou. leave them alone. always better loose than to tight.to the one who adjusted his and still has the noise i suggest that you go down to one smaller on your feeler gage and use that and adj. it to have just a little drag on the feeler gage ,that should quiten it down and still not be too tight. i have been a mechanic all of my life and it always works for me. alot of adjusting vaves is in the feel and when you get good at it you will understand what i am saying.. i hope i have been a little help at least.

[dariusld]

Originally posted by eddie440
first of all i say if its not broke dont fix it! if your valves are not making any noise and you have good power leave them alone. when you take it to the dealer for a valve adj. and its nice and quiet you can bet there not going to mess with them even if they say they did.i recomend you check them and if their within 1 or2 thou. leave them alone. always better loose than to tight.to the one who adjusted his and still has the noise i suggest that you go down to one smaller on your feeler gage and use that and adj. it to have just a little drag on the feeler gage ,that should quiten it down and still not be too tight. i have been a mechanic all of my life and it always works for me. alot of adjusting vaves is in the feel and when you get good at it you will understand what i am saying.. i hope i have been a little help at least.


Hey eddie, litttle late with the response;)

[ss440ex]

Easier to start.

[bwamos]

Too tight:
What happens.. lets say your valve adjsutment is a 0.004" (0.1mm) gap. This accounts for expansion of the valve and cam as the engine gets hot. When metal heats it expands. So your 0.004" at room temperature quickly become 0.001". If you set it to 0.002" for example and it expands.. you're going to end up at -0.001". Aka.. not sealed. On the intake stroke you're going to draw in extra air from the exhaust port that you shouldn't have in there causing a lean condition. It will burn very hot.. also as said above, the valves will not transfer their heat well.

When this happens it's very very noticable. You'll hear it, because the valves arent closed during combustion, so the burn goes past the valve into the pipe.

On the intake side.. it's less obvious, but you will get blowback into the carb and airbox.

Too loose:

The valve simply doesn't open to its full capacity, or its full duration (opens late, and closes early). Also excessive noise and wear on the rockers and cam due to the constant slapping.

Better to be a tad loose than too tight.