compression check


Anything goes - doesn't fit any other category!
  • Sponsored Links
blackbird
Posts: 53
Joined: Sat Apr 24, 2010 8:24 am
Location: Onalaska, WA
Motorcycle: 1966 305 Scrambler
1968 Trail 90
1970 Trail 90
1995 Pacific Coast
1983 GL1100A
2008 GL 1800

compression check

Postby blackbird » Mon May 17, 2010 12:52 pm



I ran a compression check on GL1100A. Engine sat for many years, but I have gotten it started. Carbs are rough, but seaFoam seems to be helping. Still very hard to start.
Question: ran a compression check(cold). #1 AND #3 are at about #150psi. #2 and #4 are at 120. Sound like a head gasket or ring problem developing?
Got the bike running this evening, and sure enough, I got a head gasket blown on the left bank. Just another learning experience. :(



User avatar
thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: compression check

Postby thrasherg » Tue May 18, 2010 11:38 am

blackbird, if the bike hasn't run for a while I would hold of jumping to any conclusions. 120PSI is high enough that the engine will run, if it has sat for a long time, there might be rust on the valve seats or bores, this will wear off quickly once the engine is running. Get it running put a couple of hundred miles on it then check the compression again. If it's still low then I would look at a problem in the engine, but at the minute it could be low because of a lack of use.. If you put a small amount of oil in the bores and run your test again it will give you an idea if the issue is due to rings or valves.. If adding a small amount of oil increases compression significantly (>20%) then you have a problem with the rings/bores, if it doesn't change much then the problem is likely with the valves.. Have you checked the valve clearances?

Gary

blackbird
Posts: 53
Joined: Sat Apr 24, 2010 8:24 am
Location: Onalaska, WA
Motorcycle: 1966 305 Scrambler
1968 Trail 90
1970 Trail 90
1995 Pacific Coast
1983 GL1100A
2008 GL 1800

Re: compression check

Postby blackbird » Tue May 18, 2010 10:58 pm

Gary
Thanks for the help/reply. I got radiator coolant out the exhaust at the junction of the pipe and the block when I got it running this last time.

User avatar
thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: compression check

Postby thrasherg » Wed May 19, 2010 11:53 am

That's not so good. If there is coolant coming out the cylinder then you have a failed head gasket or a cracked head/block.. Sounds like you do need to remove the head and find the source of the coolant..

Sorry.

Gary




Return to “Goldwing Chat”




Who is online

Users browsing this forum: virgilmobile and 3 guests