Bad day

benjamoid14 · Full Member Joined: Sep 01, 2009 Posts: 37 Location: SLC

So I bought my xs a few weeks ago with a top end noise and 1 dead cylinder. I was hoping that it was something in the cam chain making noise and mabey a bad plug or something. But last night my fears were confirmed, I did a compresson test on it and the dead side had 0 compression Sad

I have done a little research and have seen a few guys with a hole in the piston, i looked through the spark plug hole and it looks ok but i cant see the whole thing. The motor is coming out in a few days, hopefully its a bent valve or something...

AirHog · Full Member Joined: Apr 28, 2009 Posts: 21 Location: IL

Just pop on a leak down tester and see where its coming from. Did you check the other side for compression? what was it at? Did you hold open the throttle while checking? Reason i ask is because even bad engines usually have some compression. If you don't hold open the throttle you wont get much at all.

benjamoid14 · Full Member Joined: Sep 01, 2009 Posts: 37 Location: SLC

Well the right side had bout 120, and the left had 0, the guage didnt even jump. No I wasnt hitting the throttle when I did it. There is a wicked loud ping noise from the top end at all rpms, the left exhaust never gets hot, and it litterly sprays oil out the left muffler...

I pulled the valve cover things and the valves all move when I kick it. I also pulled the plugs and they both look ok, old but not damaged. Also I am getting spark on both sides.

Last night i pulled the wiring harness out and pretty much got it to a frame with an engine bolted in, so no more diag. Just gotta pull the engine and start tearing it down.

gordo · Posted: September 22, 2009, 5:07 pm Post subject: Re: Bad day

That "ping" probably a valve hitting the top of the piston. I broke a valve spring retainer& that's the sound it made. Gotta tear into it . Don't run it anymore, as you will end up doing more damage. Easy check is to check the valve clearance, a bent valve will have allot of clearance. If you did bend one, make sure you check the valve guide carefully for crack's, don't want a piece of that falling into a fresh top end job.

benjamoid14 · Full Member Joined: Sep 01, 2009 Posts: 37 Location: SLC

Well I have only ran it for a total of about 5 min, just to try to pinpoint the noise more. I have no idea how long the old owner ran it like that though. Hopefully not long, and hopefully your right about just being a bent valve. thats cheaper then pistons and such.

benjamoid14 · Full Member Joined: Sep 01, 2009 Posts: 37 Location: SLC

Well i pulled the motor the other day and tipped the motor on its side and oil was pouring out of the exhaust port... Pretty convinced that there is a hole in my piston.

bkmarsha · Posted: October 20, 2009, 1:40 pm Post subject: Re: Bad day

thats a bummer i am working on repairing the same thing on my bike

keep the updates to let me know how it goes

good luck

benjamoid14 · Full Member Joined: Sep 01, 2009 Posts: 37 Location: SLC

Im doing my hardtail right now, engine will be a project for later in the winter.

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