AXL Stubbs wrote:Good trick, BAD news. I built the tool and filled my Dirty Bird full of of air.
I could not keep any amount of compressed air in. It seemed to be leaking out the intake valves mostly. Decided I'd check and maybe lap the valves and found one #1 and #3 pitted on the faces and #4 bent.
The bike ran (not super smooth) when I started this project and I don't really want to dump $100-150 on new valves. Can I lap these valves, re-install with the new head gaskets to recheck the compression? Will the new head gasket be ruined if I'm unsatisfied with compression?
ElPiloto wrote:To find the cause of your low compression for sure, get an old spark plug and beat the porcelein out of it. Remove the ground electrode and you will be left with just the steel shell with threads to screw into the spark plug hole.
Now, braze or weld an air fitting on it so that it will snap into an air line from a compressor.
Now, make sure the cylinder being tested is at top dead center.
Screw this tool into one cylinder at a time then snap on the air line with pressure at least at 100 psi.
Listen through a hose at the intake, take off the air cleaner lid and open the throttle all the way. If you hear hissing, you have a leaky intake valve.
Then listen at the exhaust. If you hear hissing, you have a leaky exhaust valve.
Take off the oil filler and listen inside the crankcase. If you hear the hissing, you have leaky or broken rings.
You can also diagnose a head gasket that is leaking compression into the coolant. Apply the pressure and, with the radiator filler cap off, listen, and watch, for bubbles in the coolant.
mtclimited wrote:The tip as described has been used for years by me on autos.
one other thing. If you see bubbles in the radiator when you do this....Time for a headjob, and don't go there.
Pouring water in your cyl. won't tell you that!
jbz wrote:whats the trick to keep the piston at TDC when doing this test.? JB
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