compression testing ??

[superjetincairns]

i think i may have smeared my pistons into my bore during testing/jetting after a full rebuild from the crank up. I have a superjet with 82mm pistons, ada head with 35cc domes and ports matched up to the sleeves. It has had a really bad lean bog since the rebuild that i have been trying to find the cause of, I think its a faulty fuel tap leaking air into the line or a bottom end air leak but i havent pulled the motor out to do a leak down test yet. ive pretty much eliminated everything else. I did a compression test on the weekend and got 160psi rear and 150psi front cyclinder. From memory I'm pretty sure it was up around 190/195 when i first tested it after the rebuild. the motor has around 2 hours on it and most of that has been mucking around chasing the lean bog problem.
150/160 seems pretty low for my setup but i am using a different guage to my original test. does this seem normal or should i be getting higher numbers with these mods?

 

[Harbor]

Ya it seems low, can you use the gauge you used before ? If not can you get another gauge and retest ? I'd do that first but you could also pull the head and have a look

Edit: Also the short reach hose lowers compression reading by about 10 psi or so. I assume you are using the long reach hose

 

[Quinc]

Check your orings, You might have blown them. Also fix your jetting! start rich and work your way down.

 

[superjetincairns]

the hose on the guage is a lot longer now that you mention that harbour, good point!
it is also concerning to me that there is a solid 10psi difference between the 2 cyclinders.
local dealer says 5 psi max difference is acceptable.

 

[restosud]

don't worry about length of hose as it won't change your readings.accuracy of the gauge however is primordial.