Compression problem

Information and questions on GL1100 Goldwings (1980-1983)
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Posts: 1
Joined: Fri Feb 12, 2010 11:05 am
Location: CapeTown
Motorcycle: 1982 GL1100 Interstate

Compression problem

Post by Moatdg » Sun Mar 07, 2010 10:01 am

I am a newcomer to the goldwing community and appear to have a problem on my GL1100 Interstate possibly with piston rings. The engine has done 70000 kms. I have lower compression on the back right cylinder compared to the other three causing vacuum problems and slightly rough running. I have overhauled the cylinder heads to like new with new valves/seats etc having read a few suggestions on this forum, but to no avail. Is this a known fault? And does replacing the rings normally put it right, or is there something else to look for.

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Location: Utah
Motorcycle: 13 F6B
81 GL1100 (gone)

Re: Compression problem

Post by MSGT-R » Sun Mar 07, 2010 10:29 am

Loss of compression comes from four sources:
Worn Rings
Leaking Valves
Leaking Head Gasket
A crack somewhere (god forbid).

The tests:
Cranking Compression: Done w/engine warmed up and throttle wide open, engine kill switch off.
*Wet test: Same as above, but with a quick shot of WD40 to seal the rings. If the numbers come up, it's the rings. If it doesn't, it's the valves.

Leak-Down: Done with piston @ TDC and both valves closed, Keep engine in gear and hold the rear brake (have a helper). Introduce air through the sparkplug hole (you'll have to get an adapter for this) using about 40 psi on your compressor. Look for the sound and evidence of air in the intake, in the tailpipe, in the oil filler hole, and bubbles in the filler neck of the radiator.

The above tests will tell you exactly where the compression is going.

The one thing I didn't mention is the camshaft. A severely worn cam lobe will give reduced lift on that cylinder, thus making it look like a problem elsewhere. A dial indicator check on the lift will settle that question also.
Don't spook the road sheep.

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