sevenfifty Posted January 8, 2019 Share Posted January 8, 2019 Hi all! Owner of "oldschoolsuzuki" GSX750ES 1983, but new to the forum Today I did a routine valves check and tolerances was just fine on all cylinders. Then i decide to check engine compression to see how is it. I did it wiht hot engine, all plugs removed and with throttle fully open and these are the readings that i got: 1st - 132psi 2nd - 136psi 3rd - 128psi 4th - 90psi only!!! Then I put small amount of oil inside 4th cylinder and did a test again. The result was 142psi so the problem most probably is in the piston rings for me? According to manual engine has to be overhauled if there is such a difference between cylinder's compression. It's not my main bike so I ride her from time to time for short trips as I have another motorcycle to travel. Can't say that i feel some lack of power, i'm not sure as i really can't compare it with my other bike with 150hp Oil consumption is reasonable i think around 200ml/1000km Do you think it's such a big problem for 35 years old bike and what would you recommend me to do? Thanks in advance for your answers! Quote Link to comment
arnout Posted January 8, 2019 Share Posted January 8, 2019 Well.. If the engine runs fine despite the low compression on the #4 cylinder (no plug fouling?), I don't think there's an urgent need for repairs. BUT the fact that you felt the need to do said compression test makes me think perhaps the engine isn't running quite right? I think the feasibility to delay the engine (rings) overhaul also depends on the availability of quality fuel, so danger of detonation/pinging can be minimised. Another possibility to consider is that perhaps the rings aren't worn out but stuck in carbon deposits (from worn valve guide seals). Still makes taking the top end apart a necessity (unless you believe in the magic powers of aftermarket oil additives!) though.. (It is said valve guide seals can be replaced without taking the head off if indeed these are worn on cyl. #4). Quote Link to comment
sevenfifty Posted January 8, 2019 Author Share Posted January 8, 2019 Hi arnout, I do not complain about poor engine running at all. Just did the compression test as a routine task as i have the gauge. BTW last time when i checked the valves, about 2 years ago i did the compression test again and all cylinders were fine then. Anyway i also suppose there is stuck rings in this cylinder as you said, so tomorrow gonna put some kerosene to see if it helps remove carbon deposits if any. Quote Link to comment
Swiss Toni Posted January 8, 2019 Share Posted January 8, 2019 Kero might do the trick but, if you can get hold of some Marvel Mystery Oil, and it is gummed up rings, that should work. Quote Link to comment
sevenfifty Posted January 14, 2019 Author Share Posted January 14, 2019 (edited) Update: First I draw off engine oil, then I removed all spark plugs and put some amount of kerosene in each cylinder. After several hours cylinders were empty so I put kerosene again. Did this procedure 4 times total in the past two days. Today I put the old oil inside the engine again to wash the motor inside. Then started the engine to warm up and after 10-15min removed the plugs again to check compression. All cylinders are around 132-136psi and it seems kerosene did help! Did a test twice the just to be sure and everything was fine, so now i'm happy again Now I only have to put fresh oil and I'll be ready for action Edited January 14, 2019 by sevenfifty 3 Quote Link to comment
johnr Posted January 19, 2019 Share Posted January 19, 2019 excellent stuff. you may need to thrash this engine more, purely in the interests of keeping it running well.......... 1 Quote Link to comment
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