Compression test 90 psi every cyclinder

[alexis291]

Sealey make decent tools. They're not SnapOn but they're ok.
I agree with what others have said that this is more likely to be a problem with the test method than the engine being in poor condition. Those readings are very low but it's unlikely in my experience that every cylinder would be that bad.
If you want to check the gauge, do you have access to another engine (in any vehicle) which you know is ok that you can try it in?


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[RóisínDubh86]

Thanks Martin will do

Alexis yes I tried it on another engine which I knew was ok, again read 90 psi, so gauge was faulty [emoji1303]

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[wmax351]

My K75, prior to the engine replacement had some across the board and fairly even compression loss, but with a bit more in the front (iirc) cylinder. It did use some oil, but within normal range for a K bike. I replaced the engine at about 100k mile s.


On teardown after replacement with a stripped, inspected, and resealed engine, it was notable for some crowning of the cylinders, and a good deal of clearance around the pistons.


Of note, I had discovered a failed-open thermostat while I was tuning the megasquirt system, as accurate engine temperatures were displayed and logged. My guess is that this was present for quite some time, and led to a varying degree of over-cooling depending on ambient temp and load. This would also explain the somewhat varying and often low fuel mileage.