Low Compression on 04 FZ1 1000

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tommyp

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Hello All,

I have a 2004 FZ1 1000 with 140,000kms on her and the number 1 cyclinder has a compression of only 65 psi. All the othr cylinders are fine. The valves all have positive valve clearance. Any ideas or suggestions?

Also, on the same bike, I have a few exhaust valves with .004" clearance. As I understand it, this is on the lower limit of the factory spec. Any opinions on whether I should open these up a bit or just leave them?

Thanks for any help you can give.

Tommy
 
Tommy, sometimes the piston rings stick and a small amount of oil added down the cylinder's sparkplug hole unsticks them. I would do this with the engine cold and use a very thin lubricating oil like marvel mystery oil or even sewing machine oil. Only use about 1/2 teaspoon or 2 cc. Sparkplug back in and ride a few miles until the exhaust smoke stops :) Then check the compression after the engine cools a bit. If the compression comes up feel lucky and give the FZ1 more frequent oil changes.
 
I haven't gotten off my rear yet to get my service manual (hopefully a birthday gift in May) but that sounds pretty low for a machine with our compression ratio. I'd probably go with the above mentioned technique to see if that changes anything first. It's rarely a oil change issue if only one cylinder seems to be bad but who knows. The problem could be a really tight valve in the affected cylinder because if valves are opening too soon or closing late, that can have a negatve effect on compression. Although you have accumulated some miles, I've seen many bikes with twice or three times that many miles that are running fine. I know it's a pain, but we are still in winter so nows the time to get serious with the maintenance. No use waiting for summer to be here while you tear it down. You will have to do a "leak-down" test to make sure the valves and seats are good. If it's a valve issue, at least you don't have to take the cylinders off, at least I don't think. If it's a bad cylinder situation, I've seen adds for companies that can re-surface our type of cylinder lining. I'll see if I can find them and get back.
 
Thought I'd add some more thoughts. This engine has done almost 90k miles and, guessing without factory specs, should still have 120+ psi on all cylinders. Its important all cylinders check within 10 - 15 psi of each other even if the range is low. Slightly tight valves won't change compression much as long as they completely close and are not burned.

My more frequent oil change recommendation. Ring sticking in a gasoline engine is a dead giveaway to high temperature oil oxidation and often effects only one or two cylinders. If the compression recovers after directly oiling the bad cylinder, I'd even go to a higher viscosity oil for servicing to reduce oil burning and carbon. Carbon buildup on valves and seats can reduce compression too.

PS - I thought only BMWs and Goldwings lasted over 100k miles, congrads on the FZ1 and I hope mine does as well :Rockon:
 
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