Good to see people getting involved with leak down testing.
As far as numbers go ....and different tester.
The numbers I thru our we're a bit Radom and when I say that I meant exactly that. ( many here bring up good points ) suck as same tester ? What air pressure ? Cold motor , warm motor ? Hot motor ? New sled ? 250 miles , 500 miles, 750 miles 1000 miles.
Let's simplify this....
as far as tester go, we mainly use 2 different ones, ( and we and we constantly cross check them against each other. ( and someone brought up to buy the one that Indydan uses. ). Well here is where I need to explain.
We use an OTC, and a Snap on ...... Then we randomly test the import ones we sell... The import ones have been brought into offer a cheap price which was kinda stupid because they are a little random. ( but we are going to bring in only the OTC Dual gauge one. ) and stick with that. )
But let's just say we have to work with numbers from all different gauges so we can be real about all this.
Trouble shooting two stroke performance motors...... Is complex and if you are infatuated with peak performance then you should leak down test your new sled before you drive it.
Then at 250, 500, 750, 1000, 1500, 2000 and so on ( ball park of thes numbers. )
All that really matters is that either they stay very close to the same with little change from new..
Or...... The test starts out a little on th bad Side because of sub-par cylinder roundness or a below average set of rings ..... Let say 6 percent and the numbers keep getting better as it breaks in let say down to 1-1/2% to 3% and then stabilizes and flattened off.
No mater what guage, what pressure, or what technique if the numbers start to go up the need for a rebuild is coming. Soon
And here is the most important part of of all..... If the pull on the recoil rope starts to get harder and harder over time the motor on its way out.
Why does this happen you ask ? ( trust me your compression test numbers will not being going up..... ) but your leak down numbers will be going up.
What is happening is your rings and or Pistons ( most often both ) are failing and the hard pull on the rope comes from and pressure is going past the rings and pressurizing the crankcase and the motor starts fighting itself so to speak.
Don't be fooled by a great ring seal that is a crisp distinctive snap of the piston going over TDC ...... With great seperation .
Verses a poor overall hard pull that just feels ****ty and both cylinders kinda feel somewhat rolled together that lacks separation.
Leak down is the single best ( Motor ) performance trouble shooting test ( period )
Not, clutching and fuel mapping test.
I hope this helps.
Dan