Why is my compression so low

[rhuebner]

I just rebuild my motor and checked my compression it is only 120psi on both cylinders. here are the mods it have it should be higher than that right?

-68mm bore cheetah cub

-4mil hot rod crank

-hemi head with 20cc domes

-35mm pwk airstriker carbs on 109 race gas

- +7 timing

-wiesco pistons

-V-force 3 reeds

[peak-j]

Well, I dont' have the mods you do. look at my mods and I have 150 in each cylinder and motor is all stock internally. It has never been reringed yet either. Mine was 120 in each cylinder before I added the coolhead also. Hope that helps a little.

[rhuebner]

I just rebuild my motor and checked my compression it is only 120psi on both cylinders. here are the mods it have it should be higher than that right?

-68mm bore cheetah cub

-4mil hot rod crank

-hemi head with 20cc domes

-35mm pwk airstriker carbs on 109 race gas

- +7 timing

-wiesco pistons

-V-force 3 reeds

Is it cause i'm using 20cc domes? Maybe go down to about 18cc, what do yall think?

[5150banshee]

its the domes stock is close to 21 or 22 so i would go with 17 or 18 and your compression should jump to about 160 or 165 maybe more.

[Snopczynski]

porting on the cheetah's and your dome size is what affected it. Go down in dome size and check your squish with the new domes.

[pokeatyou2]

its the domes stock is close to 21 or 22 so i would go with 17 or 18 and your compression should jump to about 160 or 165 maybe more.

 

 

thats not so true im running 21cc domes and have 160psi

[Snopczynski]

Its the exhaust duration on his cheetah cylinders, could also be his elevation.

[dajogejr]

You should have way more compression...if you're at or near sea level.

 

first things first, check the squish on your motor...

Next, what kind of compression gauge are you using?

Third...did you keep kicking until the gauge didn't move? Often it can take 20 to 30 kicks.

 

my 4 mil cub with 20cc domes, NOSS head, about 600 ft above sea level put out a healthy 185PSI with .045 of squish...

[cam2]

You should have way more compression...if you're at or near sea level.

 

first things first, check the squish on your motor...

Next, what kind of compression gauge are you using?

Third...did you keep kicking until the gauge didn't move? Often it can take 20 to 30 kicks.

 

my 4 mil cub with 20cc domes, NOSS head, about 600 ft above sea level put out a healthy 185PSI with .045 of squish...

yeah, sometimes you may have to kick your a$$ off. also did you let the engine warm up first? when every thing is warmed up the piston rings will seal the cylinders a little better so you should get a higher reading then when the engine is cold.

[rhuebner]

You should have way more compression...if you're at or near sea level.

 

first things first, check the squish on your motor...

Next, what kind of compression gauge are you using?

Third...did you keep kicking until the gauge didn't move? Often it can take 20 to 30 kicks.

 

my 4 mil cub with 20cc domes, NOSS head, about 600 ft above sea level put out a healthy 185PSI with .045 of squish...

I'm at 3600 ft above sea level. This is going to sound stupid but I dont know what the squish means.

My compression tester is just a Actron, yes I should just go get me a good one for a more accurate reading but this on cant be to far off.

This 120psi reading I got was cold also.

Thanks for your feedback.

[Snopczynski]

I used to have a sears craftsman that was about 30 psi off. I also had an S&K tester that was about 20 psi off.

[rhuebner]

I used to have a sears craftsman that was about 30 psi off. I also had an S&K tester that was about 20 psi off.

What kind did you find that works the best?

[06BaNsHeE]

who built your motor.You or did you take it to a shop?

[rhuebner]

who built your motor.You or did you take it to a shop?

I built it.

[Michael Jackson]

higher you go, comprsssion lowers