bent valves

[oldyam80sg]

Just curious-everyone knows the problem i had with the cam chain tightening procedure but was wondering if the valves were indeed bent,how could you tell without removing the head?Besides the noise that something was wrong?

[bikerphil]

bent valve

Compression test. If you don't have a guage, take all the plugs out and do the ol' thumb over the plug hole while cranking test.

[rover]

Be sure to hold the spark plug wire from that cylinder in your other hand. (just joking)

[xs11jack]

NO, No. No.

Look, you need one hand free to push the starter button, so put the plug wire up your nose!

[rover]

I could think of a better place

[strom]

Well, compression test is one option but sometimes you might even get good compression.

If it works... ride it... if it doesnt, take off the engine, pull the head, valves, check them, replace if needed, grind the seats, hone the cylinders, put in new piston rings if needed, check and adjust valve clearance, replace camchain if needed, replace valve stem seals while you are at it and forget bout the top end for 100k...

[TADracer]

A bent valve would probably not seat correctly in most instances but may still seat well enough for the motor to run at some level. A leakdown test would give you a more definitive answer.

[Gyrogearloose]

I dunno', but you may indeed have a reasonable compression test, if the valve is still seating properly. Now a bent valve stem may wear the valve stem seal prematurely, and give you a fouled plug on that cylinder. The test seams to be, if the plug fouls, what kind of residue fouls the plug? Does the engine smoke? Is the residue "oiley"? Some times it's hard to tell between carbon from gas or a gas carbon- oil residue mix that fouls the plug. Perhaps the gurus has a more definitive test..without pulling the head? I'm curious; I have a plug fouling on #3 that I can't seem to get rid of through repeated carb cleaning, float settings and changing plugs. ??

[Ivan]

valve stem seals will generally not foul plugs. The most common indication of leaking stem seals is a puff of white smoke on startup after the engine has set for a while. The amount of oil going by valve stems during engine run is negligible. Older domestic V8s didn't even have seals, just a small plastic "unbrella" that deflected oil away from the valve guide.

Many times an engine with bent valves will develop enough compression to run. The problem is that the valves will burn quickly, then you will need seats as well. My thinking is that a leak down test is the way to go. It will tell you if the valves are leaking, and which ones are leaking.

TBH, pulling the head on these isn't all that bad. I took mine off in frame in about 35 minutes, and it was my first time. If you get the head off, a visual inspection will show bent valves. If you can't see any bent ones, level the head with the combustion chambers up and fill them with light oil or ATF. let it sit over night, and look for oil in the intake or exhaust ports on chambers that have lost oil. Also use old plugs, as the oil will foul them.