Need Help!- Bent Exhaust Valve

[Soultaker696]

Hi, I've been looking at buying the BMW my neighbor has, but it has a small problem... In the second cylinder it was losing compression so my neighbor took thew head off and noticed that the exhaust valve wasn't closing. I was wondering if the valve could possibly be bent or if there could be some other problem? Any insight into this would be greatly appreciated. I can even get some pictures of the cylinder head if need be. Its a double overhead cam off of an '86 BMW 325e, the motor is an M20.

[2muchstuff]

It could be bent- Did the timing chain slip getting things out of time. If so there could be more valves bent.

It could be siezed- Lack of lubrication, burnt/ overheated valve.

Either way the valve needs to be removed and replaced and the valve guide inspected.

[Soultaker696]

I really don't know what happened to it, the guy i'm buying it from got it like this. He checked each of the cylinders for compression or lack thereof and i guess found that only the second cylinder was losing compression. If I had the tools I'd take the head apart myself and look at the valves, but alas I do not.

I too thought that the timing could've had something do to w/ it, but then i thought that it the valve itself were bent then wouldn't there be a dent in the piston where it would've hit the exhaust valve, which there isn't.

Thanks for your input though, I'll look into it.

[MrWild]

Two ways the valve could be lifted off it's seat. One way is if it is bent. Another way is if there ius a lot of carbon built up on the stem. Possible ways the exhaust valve got bent is a previous owner missed a shift while racing or being a squirrel, and over revved the motor. The timing chain/belt doesn't need to have skipped a tooth for this to happen. Another way is if the timing belt./chain did skip a tooth. It'd have had to be rediculously worn out though. One other way is for the valves not getting a proper amount of oil, and the valve stem galled resulting in the valve hangng open and getting hit with the piston.

What you should look at is the piston crown and if it shows signs that it hit the valve. This would be evidenced by a lack of carbon deposit or flattened carbon deposit where it came in contact with the valve. Go out and buy a valve spring compressor they aren't that expensive.

If you're thinking of buying this bike, only give pennies on the dollar. A bent valve is a warning that you will find other problems from an abusive prior owner. BMWs are not cheap to work on, and when these other problems rear their heads, you will be crying if you paid a pretty penny for this trouble on wheels.

[Soultaker696]

Hmm, the valve in that cylinder doesn't look any different from the other 5 exhaust valves except for the fact that it sticks out a lot father than the rest. I can't tell from looking at it if its bent or not, but my buddy's dad has the proper tools to take the cam off and pull the valves to inspect them so i'm gonna have him take a peek for me.

[tullsa]

probably figured it out by now ,my 2 cents would say look for a broken spring /damaged pushrod or lifter