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I have a Yamaha F250 that blows smoke above 5000 rpm from oil getting into intake manifold (via breather tube). Not an uncommon problem for these early F250's, but it didn't do this prior to powerhead replacement. PH has about 300 hours on it since replacement and regular use of ringfree. Exhaust system was replaced earlier in its life too.
Anyway, the instructions on the OTC brand leakdown tester warn not to set the regulator from compressor any more than 10psi from the pressure used on the tester...
So in this case, I limited the regulator on the tank to 110 and set tester to 100 psi.
The problem I'm having is that when I adjust the tester dial to build psi up to 100, it can only climb to about 60 (leakage gauge follows it within 2-3%), then it'll suddenly drop pressure down to ~30 psi (again with leakage gauge still matching the pressure gauge).
Thinking the regulator could be faulty on my compressor, I set it to 125 psi and slowly but successfully adjusted the tester to 100 psi. With this adjustment, I'm only seeing 2-3% leakage on the gauge (97-98 psi). Also tried 90 psi on tester and had same good results (too good to be true?). I feel like this rules out cylinder not being on TDC.
With regulator on tank set to 110 (tester could not reach 100 psi, got to 60 then dropped to 30)
Anyway, I'd already bought a quart of Yamaha internal engine cleaner, so ran the engine in a horse trough for 1 hour @ 1500 rpm off a small tank (with 32oz YIEC and 1.25 gals gas). Also gave it a 15 min break halfway through to drain and refill tank with cold water.
Barely any smoke the entire time, so pulled plugs (surprisingly clean) and retested leakage... still had the issue with sudden pressure drop (110 from compressor regulator), but got ~2-3% on all cylinders when adjusted compressor regulator to 125psi (with 100 on tester).
Do I have a faulty regulator on my tank? Or am i doing something wrong in this process?
Thoughts?
**No smoke makes me think it didnt need a de-carb, and if it is only 3% leakage, clearly its not rings... I also have an oil breather tube "T" joint and oil isnt overfilled (done the whole yamaha procedure of tilting up halfway while warm, waiting 5 mins, then tilting down and checking).
Anyway, the instructions on the OTC brand leakdown tester warn not to set the regulator from compressor any more than 10psi from the pressure used on the tester...
So in this case, I limited the regulator on the tank to 110 and set tester to 100 psi.
The problem I'm having is that when I adjust the tester dial to build psi up to 100, it can only climb to about 60 (leakage gauge follows it within 2-3%), then it'll suddenly drop pressure down to ~30 psi (again with leakage gauge still matching the pressure gauge).
Thinking the regulator could be faulty on my compressor, I set it to 125 psi and slowly but successfully adjusted the tester to 100 psi. With this adjustment, I'm only seeing 2-3% leakage on the gauge (97-98 psi). Also tried 90 psi on tester and had same good results (too good to be true?). I feel like this rules out cylinder not being on TDC.
With regulator on tank set to 110 (tester could not reach 100 psi, got to 60 then dropped to 30)
Anyway, I'd already bought a quart of Yamaha internal engine cleaner, so ran the engine in a horse trough for 1 hour @ 1500 rpm off a small tank (with 32oz YIEC and 1.25 gals gas). Also gave it a 15 min break halfway through to drain and refill tank with cold water.
Barely any smoke the entire time, so pulled plugs (surprisingly clean) and retested leakage... still had the issue with sudden pressure drop (110 from compressor regulator), but got ~2-3% on all cylinders when adjusted compressor regulator to 125psi (with 100 on tester).
Do I have a faulty regulator on my tank? Or am i doing something wrong in this process?
Thoughts?
**No smoke makes me think it didnt need a de-carb, and if it is only 3% leakage, clearly its not rings... I also have an oil breather tube "T" joint and oil isnt overfilled (done the whole yamaha procedure of tilting up halfway while warm, waiting 5 mins, then tilting down and checking).