Super Jet Ada head and domes not getting right compression. Need advice

S

superjetchet21

Location
United States
Hey guys i just recently bought a 06 sj with ported/polished 701 with ada head and 33 cc domes and it isnt getting anywhere near the psi ada says it should be getting I dont know if it was over ported or if that even has anything to do with it. I tested the compression with multiple testers and tested it with the throttle wide open on a new battery and im not getting anything over 150 in both cylinders. I even had a brand new set of rings and pistons I tried for the hell of it and same psi. Just wondering if the porting maybe the problem or what? im totally lost. I dont know if just throwing different domes in it would help bring the psi up?
- Ada Head 33cc domes
- delta 3's
- Factory B pipe
- Dual mikuni 44s
- msd enhancer and lightened flywheel

thanks guys
 
Blue

Blue

Judging your cheapness
Location
St Cloud Florida
Possibly overported if the builder raised the exhaust port the compression will not be the same as ada recommends. Are you sure the bore is not to worn out or oversize? But mostlikely over ported.
 
Trubski

Trubski

Location
Boca Raton, FL
I have the same problem but I'm at 165psi, the motor is lightly ported and runs awesome, my mechanic say if the psi is the same in each hole, leave it alone. Plus lower compression is safer

is you motor running poorly?
 
S

superjetchet21

Location
United States
all great ideas thanks guys! I may throw the stock head on there and retest compression I also have 84.50 mm pistons and my buddy owns a machine shop he is willing to re-sleeve and bore but its going to run me a little and I want something I can just get on and go but still has good power, I already sold my stock 38s too tho and bought dual mikuni 44bns. I may just keep the 701 top end and downsize in dome size. Would I get much gain out of using the dual 44s on the 701 top end?
 
motozachl

motozachl

uPsiDeDoWn
Location
JAX
Use a good gauge when checking compression. My harbor freight one was about 150 while the snap-on read 185psi
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
38s will hit hard on the bottom with the correct porting, but i think 44s are better. i run 48s on everything, for the same reason the dog licks his nuts, cause he can. its not a good idea to boost compression on a tired top end, just for the sake of raising it. if the comp is low due to raised port heights, then raise comp. but like fast superjet chase states,cranking comp aint running comp and if the ports were raised to the moon, running comp will be to the moon and needs race gas or it will grenade. if it runs good now and is tuned correctly, ride it like a rental.
 
rollin5150

rollin5150

Location
Idaho
In my experience, ADA specs are off from actual. At least in the kawasaki world. They state 32CC domes should be getting about 185psi. Almost everyone I know that put those on gets 150. We all run 28cc to get the desired compression of 180.
 
Nuklear6

Nuklear6

I Dream 10' Surf!
Location
Bordentown, NJ by week / Brigantine, NJ by weekend
superjetchet21 said:
its about 3.7 mm on both ports from top of port to top
Click to expand...

Im gonna assume you mean 37mm not 3.7. At 37mm (1.456"), assuming your cylinder is stock height and hasnt had any material decked off the top, that is quite high exhaust port timing. Still not sure if thats high enough to lower the cranking compression over 30psi. Would check piston to cylinder wall clearance just to see how wore the bore is, just to be safe.
 
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