Even though the 1981 Suzuki GS650L is still in no condition to run and a compression test should be run on a warm engine, it is still a good idea to determine what kind of compression the engine has before spending time working on other components of the engine. If the compression is low on one or more cylinders, there are bigger and more costly issues to be solved first.
In a warm engine compression test for this engine, each cylinder should have a compression reading between 142 psi and 199 psi and no more than a 28 psi differential across the compression readings.
I pulled the four spark plugs to perform the compression test and also thought that they would give a good indication of how the engine was running in the past. Doesn’t look like it has been run much at all with these spark plugs.
Next I had to get the engine to turn over. I installed a Yuasa YUAM62H4L YTX14AHL-BS Maintenance Free Battery instead of the original equipment Yuasa YUAM2214Y YB14L-A2 Battery which obviously requires maintenance, breather hoses, and puts out corrosive gases. I don’t think I have ever had to add electrolyte to a battery.
With the keys obtained from Hawaii, the battery installed, plugs removed, and a compression gauge (OTC Tools – http://bit.ly/RmjM8y) connected it was time to crank over the engine. Here are the results:
- Cylinder 1 – 168 psi
- Cylinder 2 – 180 psi
- Cylinder 3 – 150 psi
- Cylinder 4 – 180 psi
Everything was within spec, even when cold. I sprayed some PB Blaster in Cylinder 3 and it came up to 165 psi. Very satisfied with these results on a cold engine.
Next will be the biggest challenge for me, I hope, rebuilding four carburetors…