Super Jet need help comp is low

[Poizen]

Hey guys

Just installed my bored 701 to 760 61x cylinders put im new domes for the 760 38cc which should give me 180psi but im only getting 150psi equal in each hole tested cold but doubt warm will make a extra 30psi

Rings are gapped to 0.3mm
Bore 84.05mm giving me 0.1mm piston clearance

What will cause this only thing I can think is the head of the pro-x piston isnt right

Im not worried about it being low as ita more reliable but I like the extra for the punch

Suggestions are welcome

Might put my 701 35cc domes and see what that gives

 

[tor*p*do]

many times compression is low until rings "set"
get a few run hours on it and re-check

 

[Poizen]

Cool thanks

Hope this is the case

 

[tipafew]

Or porting is high....

 

[Poizen]

I made sure I didnt touch the exhaust port roof

 

[OCD Solutions]

My ported 760 cylinder was at 150 with a 38cc dome as well. I had to go to 35cc domes to hit the 185 mark.

 

[JT_Freeride]

My ported 760 cylinder was at 150 with a 38cc dome as well. I had to go to 35cc domes to hit the 185 mark.

I just put a ported 735 with 35cc domes and it read 235 psi before break in and now it reads 205 psi. Did you guys check with different gauges. And dumb question are you at sea level?

 

[JetManiac]

Hey guys

Just installed my bored 701 to 760 61x cylinders put im new domes for the 760 38cc which should give me 180psi but im only getting 150psi equal in each hole tested cold but doubt warm will make a extra 30psi

Rings are gapped to 0.3mm
Bore 84.05mm giving me 0.1mm piston clearance

What will cause this only thing I can think is the head of the pro-x piston isnt right

Im not worried about it being low as ita more reliable but I like the extra for the punch

Suggestions are welcome

Might put my 701 35cc domes and see what that gives

701 domes only good up to 83mm pistons

many times compression is low until rings "set"
get a few run hours on it and re-check

That would be my advice also.

 

[Poizen]

Im at sea level

Ran the ski on thw hose today for 2x15min sessions warm up and cool down and repeat

Tested and im getting 175psi now yay what a relief still 10psi short but im happy will test with my other gauge tomorrow

cant wait to get out and feel if I did a okay job with my porting seams snappy with the little blips I did