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Minimum Compression Spec? 79 1000e

open1mind

open1mind

Forum Apprentice
Past Site Supporter
I have a mint 79 gs 1000e, and I have most of the bike sorted both cosmetically and mechanically. In a recent trip to a dealer (for the required annual NY State Inspection sticker), I asked them to check the compression--- only because I never have after a few years of owning this gem.

I was disappointed to hear the numbers. In cylinder order it was 110, 100,100,100. That sounds pretty low to me. The bike has 12000mis on the clock, runs very strong, and does not make any troubling noises. if you review my other posts you will see some manageable headaches with fuel/electrics, but they were solved through a combination of a) capable advice from the GSR wizards here, and b) some mostly capable techs once I started using the right service people. I dont wrench much myself for some life/time/family reasons.

AZR capably rebuilt and sold me a full bank of replacement carbs that are going on over the winter. A prior dealer CLAIMS to have adjusted the valves about 1500mis ago-- but I am not sure.

My take away is that I planned to keep riding this summer, but when the carbs get switched out over the long winter to have the valves adjusted again. Thoughts?
 
Have you adjusted the valve clearances yet?
Those numbers are typical for an engine with neglected valves.
We get this every day.
 
"Thoughts?" Sure.

How was the compression test done? It is supposed to be done on a warm engine, with the throttle held wide open, AFTER assuring proper valve clearances.

1. You THINK the valves are OK because a prior dealer claims they were done.
2. You don't KNOW how the compression test was done.
3. The manual calls for compression pressure of 128-184 psi, with a service minimum of 100 psi. If the test was done incorrectly, you should have higher numbers than what they reported.

Bottom line, I don't think you have anything to worry about at this point.

.
 
Dealer's job 1 is to sell new motorcycles. Keeping old ones on the road is in direct conflict with this. They are not all as honest as you might imagine.

At the very least check the valve clearances yourself and do the compression test yourself.
 
Ok, some good advice on one point. The dealer (in this case one with a proven track record and seasoned techs for my other bikes- indian, victory), was honest and said that they did the compression check cold because that is apparently the spec on their other lines. As you stated, they are supposed to be done on a warm engine, open throttle etc. Those things did not happen so the correct measurement would have been higher, perhaps a lot higher.
Just in case I wasnt clear, the valves will get done over the winter as part of the carb swap. My question, more accurately put, was whether I should hesitate to keep riding it all summer. Given the responses here, and the fact that I put a long ride into it yesterday with lots of power and no problems, I am plan to put it out of my mind until the off season.
 
If they did not open the throttle all the way then they got a bad or low reading 100psi with the throttle closed is pretty good compression. I do not understand why they would not open the throttle up during the test though. I do my bikes with the carbs off. With CV carbs you have to remove the carbs to get a true reading
 
Do the valves now or risk destroying the cylinder head and valves over the summer. Valve adjustment should NOT be neglected.
 
Just circling back to this long forgotten thread. Duly noted about not letting valve clearances get too bad. As planned, I had a trusted tech do some work on the bike over the winter. Specifically, a full replacement of the carbs (rebuilt's source from our own AZR), new intake boots, stainless screws... and a valve adjust with a new gasket and halfmoons. I even bought the specialized tool for the job. The good news- no valves needed re-shim work. Given the gentle treatment and low miles on this bike (10k), I am not surprised. Short ride says it is better than ever, even though it was never bad. Hoping for more sunshine soon to get more miles on to check for any fine tuning needs.
 
stetracer said:
I do my bikes with the carbs off. With CV carbs you have to remove the carbs to get a true reading
Click to expand...

I didn't know this. Would doing the compression test with the carbs on give a falsely low or falsely high compression reading?
 
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