compression


Information and questions on GL1000 Goldwings (1975-1979)
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bull42
Posts: 1
Joined: Tue Jul 16, 2013 5:51 pm
Location: Beaumont, Texas
Motorcycle: 2005 GL1800 Trike
1978 GL1100
2004 GL1800

compression

Post by bull42 »



Well a couple of years ago I sold "The Beast", my '79 GL1000 in the name of raising money to purchase a GL1800. I have regretted it ever since. I recently bought a '78 to replace it. This one isn't a beast, it's a Frankenstein's monster! I have a '78 chassis with a GL1100 engine and '76 carbs. The bike has been sitting in a garage for a couple of years is a state of semi-disassembly. It was obvious that the carbs need to be rebuilt so I got what's needed from Randakk and got after it. Spent 2 full days meticulously cleaning and rebuilding the carbs. I re-installed them and the bike fired right up. However, all is not well.
It is running great on the right-side cylinders (1 & 3) but is not on the left. It pops erratically through the exhaust, so I began troubleshoot a lean condition. The plugs did not support that surmise. They seem to indicate that these cylinders are not running at all. There are no vacuum leaks on them. There is good spark. They are in time. Valve lash is correct. Compression is very low. This is where I get a bit confused. My experience says that compression is either good OR it is consistently low. These 2 cylinders are all over the place. Consistently 60 psi or above, but I occasionally get up to 120psi. I ran and re-ran the test with these results. I noticed that if the engine was running on the other 2 cylinders (the darn kill switch is bypassed) that I never got above maybe 80psi (usually 60 for the worst one... number 4), However, when just cranking it over I get varying results. I noticed that I can usually get the compression reading up by stopping and starting the starter. it will jump up on the last compression stroke (usually). Doing this several times in a row without releasing the pressure in the gauge I can sometimes get the compression reading on these 2 cylinders up to 120psi. I have been wrenching since the 60's but this behavior is new to me. Please share with me any insight you have.
I am hoping for sticky valves but fearing sticking rings.


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virgilmobile
Posts: 9088
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: compression

Post by virgilmobile »

Compression test done with cold engine,all plugs removed,no spark,wide open throttle..
Each cylinder needs a minimum of 80psi to fire(badly)...crank the engine for 5 seconds per cylinder only.
Erratic compression would lead me to think a valve isn't snapping shut due to sticking or a broken valve spring.
As I recall each valve has 2 springs and I've seen the inner spring broken.Its replacement can be done without removing the head.
Old Fogey
Posts: 839
Joined: Fri Oct 30, 2009 2:09 am
Location: Glasgow Scotland
Motorcycle: 1976 GL1000
1979 GL1000
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Re: compression

Post by Old Fogey »

Sticky rings are a given on these engines if left sitting for any great length of time. But not really a worry. If it will pull you down the road without shaking itself to bits, go thrash the living daylights out of it and you can be almost certain that the rings will free off.
'Impossible' is just a level of difficulty! The only stupid question is the one you didn't ask first!

( Seriously, you haven't read all 115 pages of my http://www.wingovations.com website ?? :shock: )
User avatar
virgilmobile
Posts: 9088
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: compression

Post by virgilmobile »

The phrase.."ride it like ya stole it".


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