T
thompd84
Guest
Hello Everyone,
I picked up a 1980 GS550 in a bike trade a couple of months ago and have been working though all the issues that you have with a dead bike that has not been run in seven or eight years. This site and the Basscliff site have been a gold mine in useful info and resources and my thanks to all who have taken the time to put it together.
During the initial evaluation I found no spark on Cylinders 2-3 (which is probably the reason the bike had been sitting) and stuck fuel floats with fuel running out of the air bleed ports in the back of the carburetors. I had to replace a smoked ignition module with a Dyna S to get any spark and now the bike will start and run for a short period with a spray of starter fluid. I ran a compression test on the bike during the initial evaluation also and found that cylinders 1 and 4 had about 90-95 Psi and in 2-3 there was only 75 or so. Not too great but I don't know if I want to read too much into a compression test on a cold bike with possible sticky rings). Anyway I dumped some oil in the cylinders and they all popped right up to a respectable 135 to 155 range so I put that issue on hold for a while till I could get the bike warmed up and get a good check. I still need to run a leak down test on the cylinders to see if the head gasket is leaking and the condition of the valves but I will have to borrow a tester from my Dad. That test should also be run on a warmed up engine for good results.
Since then I have been working though the carbs and after a couple of half hearted attempts at a quick cleanup I am in the process of the full teardown and cleaning and O ring replacement as per this site.
Anyway, I wondered if anyone had any info on what the minimum compression could be and still have a cylinder fire with standard jets and tuning. I hate to go chasing carburetor issues if I have a mechanical problem and the compression is insufficient for the plug to fire the mixture.
Thanks
I picked up a 1980 GS550 in a bike trade a couple of months ago and have been working though all the issues that you have with a dead bike that has not been run in seven or eight years. This site and the Basscliff site have been a gold mine in useful info and resources and my thanks to all who have taken the time to put it together.
During the initial evaluation I found no spark on Cylinders 2-3 (which is probably the reason the bike had been sitting) and stuck fuel floats with fuel running out of the air bleed ports in the back of the carburetors. I had to replace a smoked ignition module with a Dyna S to get any spark and now the bike will start and run for a short period with a spray of starter fluid. I ran a compression test on the bike during the initial evaluation also and found that cylinders 1 and 4 had about 90-95 Psi and in 2-3 there was only 75 or so. Not too great but I don't know if I want to read too much into a compression test on a cold bike with possible sticky rings). Anyway I dumped some oil in the cylinders and they all popped right up to a respectable 135 to 155 range so I put that issue on hold for a while till I could get the bike warmed up and get a good check. I still need to run a leak down test on the cylinders to see if the head gasket is leaking and the condition of the valves but I will have to borrow a tester from my Dad. That test should also be run on a warmed up engine for good results.
Since then I have been working though the carbs and after a couple of half hearted attempts at a quick cleanup I am in the process of the full teardown and cleaning and O ring replacement as per this site.
Anyway, I wondered if anyone had any info on what the minimum compression could be and still have a cylinder fire with standard jets and tuning. I hate to go chasing carburetor issues if I have a mechanical problem and the compression is insufficient for the plug to fire the mixture.
Thanks
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