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Discussion Starter · #1 ·
I've performed leakdown tests on 2-strokes. I'm sure I can figure out how to do my Bomber but, I thought it best to querry you folks.

I suspect I'll need to do one cylinder at a time. Go through spark plug? How long to hold how much pressure ? Can you tell where any pressure lose is ? Rings, intake, exhaust, head gasket ?

....see, I probably need a procedure spelled out to me !

Did a search here to no avail....

ThX for any advise....
 

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A leak down tester is screwed into the spark plug hole with that cylinder's piston at TDC on the compression stroke.
Then air, lots of air is applied. At least 125psi.
Once you have the air applied, you will hear where the air is escaping from if you have a leak.
It will come one of or all three places, exhaust, air box/carbs or crank case vent.
If it comes out of your exhaust, it is a bad exhaust valve.
If it comes out of the air box/carburetor, it is a bad intake valve.
If it comes out of the crank case vent, it is bad rings or a hole in the piston.
 

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You can also have air come out of the mating surface between the head and the cylinder barrel. If this leaks into the cam chain valley, the sound will be evident with the cam covers off. A mechanic's stethoscope with the probe end removed, leaving the end of the tube open is good for pin pointing escaping air sounds. With luck, there's a chance a head re-torque could cure the problem. something not mentioned is that you have to lock the crankshaft with the piston at TDC compression to do the leakdown test, which you would have had to do with the two cycle. Except that your crank has to be in the valves closed position, the cylinder leak down test is otherwise the same.
 

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KERRY said:
You can also have air come out of the mating surface between the head and the cylinder barrel. If this leaks into the cam chain valley, the sound will be evident with the cam covers off. A mechanic's stethoscope with the probe end removed, leaving the end of the tube open is good for pin pointing escaping air sounds. With luck, there's a chance a head re-torque could cure the problem. something not mentioned is that you have to lock the crankshaft with the piston at TDC compression to do the leakdown test, which you would have had to do with the two cycle. Except that your crank has to be in the valves closed position, the cylinder leak down test is otherwise the same.
I forgot about the possibility of a bad head gasket, sorry about that. :roll:
 

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Your leakdown tester should have instructions - mine specifies 90 psi as a max. The instructions will tell you how to interpret the 2'nd gauge of the rig.......

It's absolutely critical to keep the piston from going past TDC - the rings have to be in the bottom of the ring grooves, so if you overshoot at all, you'll need to rotate all the way around (twice, so you're on compression stroke) again. No "backing up".....
The 180 degree twins will try to roll past TDC on you, so it takes a bit of technique to get it right.
And the other spark plug should be in place.

Everything Ray says is good info, concerning what and where to listen for.......
 

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Discussion Starter · #6 ·
Thanks guys....learned a few things. I appreciate the help.
 
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