i need some help with new motor....

bign1514

bign1514

"Rock-Man"
Location
Louisville, Ky
I broke my new motor in the weekend and have receieve some compression numbers that are starting to scare me. My set-up is....

82mm bore
freestyle port
ADA girdle kit with 33cc domes

My compression on front cycl. is 162psi and the rear is 175 psi after break-in. Before break-in the front was hitting 178psi and rear 190psi. I went through one tank of gas varying the throttle from idle to 1/3. Then did a compression test after break-in and received the above numbers.

Also the ski was hard to start every time I tried to start it. It was always take a good 5-8 seconds before starting (i am guessing a carb rebuilt).

I am using the Weisco pistons and rings. Could maybe these rings be bad or anything? I have check the cycl wall and ran my figure around and couldn't feel any scouring - cycl. look like new.

Anyone have any ideas where i can start to get this engine running the way its suppost to be? Any help would be greatly appreciated.
 
wsuwrhr

wsuwrhr

Purveyor of the Biggest Brapp
Location
Alta Loma, working in Upland
Could be a couple things.

Most likely it is two different domes.

I would start by checking the dome CC to be sure, sounds like the domes may have been mismarked.

One quick easy check, where the spark plug screws into the dome there is a counter bore(step), are the steps the same depth, are you able to measure it? If not, look at the base of the spark plug, does it look like they are at the same level?

Probably best to take the head off and the domes out and make sure they are the same cc.



Brian
 
bign1514

bign1514

"Rock-Man"
Location
Louisville, Ky
i tested the gauge, and it should be good. Its a new Professional Craftsman gauge. (not the best but not cheap either)

I know the domes are 33cc (from there markings) i will check and measure the volume of the dome itself are correct.

Any other suggestions? Thanksd for the information.
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
bign1514 said:
i tested the gauge, and it should be good. Its a new Professional Craftsman gauge. (not the best but not cheap either)

I know the domes are 33cc (from there markings) i will check and measure the volume of the dome itself are correct.

Any other suggestions? Thanksd for the information.
Click to expand...

wsuwrhr said:
You're welcome.

Just because the domes are STAMPED "33" doesn't mean squat.
Click to expand...

Brian is correct, if you look at the domes, the stamping is done by hand with an engraver. who is to say that the person grabbed the wrong dome and marked "33" on it.

Also, you may have a bad oring causing you to loose compression. the oring may have slipped out of the groove when you installed it. Did you grease the orings before you installed them?
 
bign1514

bign1514

"Rock-Man"
Location
Louisville, Ky
i swapped the domes around for compression.... still the same! so no oring or dome mismatch.

Anything I am missing?

Is there any way the piston rings could of been slightly damage when installing them?
 
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