What could cause low (but not no) compression? The Starfire had been a bit reluctant to start then just died after about 5 minutes of riding. I've got fuel getting there, sparks, I've checked the EI hasn't slipped on the tapered rotor, so spark timing is OK. I'm showing about 75psi.
I checked the pushrods are free to spin as per Rupert ratio so I don't think the valve clearances have closed up. Put a bit of oil down the bore and that's impeded the compression based on kickstart feel, I'd put the test away by then.
And then how do I fix it? Thanks in advance all!
Low compression problem
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- Crofty1984
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Re: Low compression problem
I take it that impeded is improved, if this is so your rings are worn. I had this problem with mine, it had been started and run without the bore being checked and the rust slowly ground ground thing away.Crofty1984 wrote: ↑Sun Mar 10, 2019 10:14 pmPut a bit of oil down the bore and that's impeded the compression based on kickstart feel, I'd put the test away by then.
Doug
Should never have sold them old motorbikes
Should never have sold them old motorbikes
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Re: Low compression problem
Knackered piston rings take a while to wear down and start to smoke badly.
Sudden loss of compression can be due to a chip off a valve face or eroded seat. Doesn't take much to bleed off PSI. Pull the head and have a good look, best also to remove the valves and either replace or recut.
Sudden loss of compression can be due to a chip off a valve face or eroded seat. Doesn't take much to bleed off PSI. Pull the head and have a good look, best also to remove the valves and either replace or recut.
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- kommando
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Re: Low compression problem
Even a small loose piece of carbon stick to a valve will do it, once it comes off normal service will be resumed. Had it on a C15 that stopped on way to work, 50 easy kicks later it restarted.