Not Bent Valves! Head Gasket Issue!

So my 1980 KZ250 that was giving me problems, is in the hands of a mechanic. He has told me that the bike has a bent valve. He said that he can get the bike running good, but not to hang on to it for long. How long can you run on a bent valve in a 1 cyl. motor?

Thanks

Not long. A week, a day, an hour. The better question is why would you ride it at all?.

Is the Mechanic suggesting you get it running and sell it to someone before it breaks?.

Fix it first or tell the new buyer what is wrong with it...Russ

When the motor turns to shrapnel it to late. If you know its bent don't ride it unless you need a shiney boat anchor.

First I would ask how does he know it's a bent valve? Did he pull the head and see this condition? If so, what caused it to be bent? Valves don't simply bend unless they come into contact with something hard (like a piston or another valve). Anyway, if he pulled the head he should be able to determine what bent it (whatever it was may also be damaged), and if he pulled the head why not simply fix it while it's apart? Did he say how he was going to get the bike "running good" with a bent valve? I'm no professional mechanic, but this doesn't seem possible to me as the bent valve isn't likely to seat well enough to seal the head for compression. You may want to get a second opinion. Ed

if a single cylinder engine has a bent valve it won't run as the engine will not have any cylinder pressure cylinder, pressure will escape thru the valve seat of the bent valve please find out how this genious has come to the conclusion that the valve is bent.

Russ Jackson wrote:

Is the Mechanic suggesting you get it running and sell it to someone before it breaks?.

That's what it sounded like to me......:huh:

dearthchris wrote:

He has told me that the bike has a bent valve. He said that he can get the bike running good,

As the others said...those two statements are not compatible...the bike can't run good w/bent valve...it can't even run...change mechanics. :blink:

Thanks guys. Yeah he basically said get the bike running and sell it right away. I am not a mechanic by any means but I didn't think a motor would even run / idle if a valve is bent? How many valves would my bike have? Could the timing being wrong bend a valve? He was under the impression that the valve has been like that, and that the previous owner pulled on over me. I paid 650 bucks for it, it's my first bike that I am learning on. I wouldn't want to scam the next person that buys it from me, I truly just want to ride it.

Your bike only has two valves (inlet and exhaust)...If even one is bent, then the combustion chamber isn't sealed at the correct time and you can't have compression and combustion = no running. Yes, a jumped and or stretched timing chain can cause a bent valve. BUT, if the bike runs, then it can't be a bent valve. I think this mechanic is putting one over on you and just doesn't want to work on the bike.

Why not just get it fixed and start riding?

ive seen plenty of motors with cooked valves and bad rings that ran,some of them ran suprisingly well! :laugh:

Had a brother-in-law who was the world's best mechanic (according to him!). Rebuilt a Z1 motor and started it up. Bent every valve in the motor. Had the cams off by a tooth I believe (been years ago). Made noise but ran good considering. Motors will run with a bent valve. Depends on the degree of bend. A motor can run with too tight valve clearances to. It just won't be as good as it could be if everything was right. Best, if wanting to keep it, to just get it fixed and be done with it so you won't worry about it later. Peace of mind is priceless at times.