is this right ?

[Jaystre]

ok so i ruled out the faulty gauge ... so how much octane is needed when running 190 psi of compression and do u calculate compression ratio?

[Jaystre]

would not having a spacer plate under the cylinders change how much cranking compression i am getting ? because the port timing would be off.

[bansheesrtoys]

well i am running a spacer plate under my jugs with no porting and 19 cc domes and i'm at 175psi and run 100 race gas stock timing .and it runs perfect.

Edited December 28, 2010 by bansheesrtoys

[Jaystre]

well i am running a spacer plate under my jugs with no porting and 19 cc domes and i'm at 175psi and run 100 race gas stock timing .and it runs perfect.

are u at sea level or close ... i have 21 cc dome and 190 psi . where did u get those spacer plates??

[bansheesrtoys]

741ft above sea leveland the spacer plate came with my crank when i bought it. but i think vitoes will sell the plates by them selfs.

[Jaystre]

741ft above sea leveland the spacer plate came with my crank when i bought it. but i think vitoes will sell the plates by them selfs.

thx for sharing your setup info! at least i know im heading in the right direction

[tedd1]

What is the squish on this motor?

[Jaystre]

ill have to check nothing change since the rebuild but ill let u know soon .

[Jaystre]

What is the squish on this motor?

squish is around .038 -.040

[tedd1]

squish is around .038 -.040

 

Getting that up ~0.050" with a thicker base gasket would get you a lot closer to where you want to be.

[Jaystre]

Getting that up ~0.050" with a thicker base gasket would get you a lot closer to where you want to be.

yeah id like to run regular pump gas a lot cheaper and way more convenient ! you think a thicker base gasket would get me in the 150 ish psi range or it would not make that big of a difference?

[bigboybanshee]

yeah id like to run regular pump gas a lot cheaper and way more convenient ! you think a thicker base gasket would get me in the 150 ish psi range or it would not make that big of a difference?

 

Just so I'm on the same page here...

 

You have a 4mil stock cylinder that hasn't been ported for a 4mil, and you're running a spacer plate on TOP of the cylinders, correct?

 

If so, it sounds like you need to move the spacer plate to the bottom of your cylinders. That way it moves your cylinders up to put the port timings where they should be. Then try checking your compression again.

 

21cc domes at or around sea level should put you around 150 psi compression, stock porting. You could run 93 pump gas and advance your timing 4 degrees and be safe with that compression and squish.

 

I would not mess with the thicker base gasket to adjust your squish. It'll change your port timings. Honestly, I think your squish is fine. I try to shoot for close to .040

[Jaystre]

Yep thats about it ! i bought this bike and it was all messed up as im going thru the rebuild im finding some weird stuff hehe ...but slowly i am making this right or trying too at least . ive ordered the spacer plate that goes under the jugs when it arrives ill install it and recheck compression . how can changing the spacer plate from top of jugs to bottom of jugs change compression that much ...does it have to do with port timing?

[bigboybanshee]

Yep thats about it ! i bought this bike and it was all messed up as im going thru the rebuild im finding some weird stuff hehe ...but slowly i am making this right or trying too at least . ive ordered the spacer plate that goes under the jugs when it arrives ill install it and recheck compression . how can changing the spacer plate from top of jugs to bottom of jugs change compression that much ...does it have to do with port timing?

 

Yes, it affects when the piston passes the ports.

 

Putting the spacer plate above the cylinder basically just keeps your piston from smashing into the dome with the 4mil crank. The purpose of the spacer plate is to move your port timings up to match the 4mil crank, AND to keep the pistons from smashing into the domes. Being that your piston is not in the correct spot in the cylinder means it's not passing over the ports correctly and I imagine that would have an effect on your compression reading.

[Jaystre]

ok thx a lot ! I will let u guys know what happens i installe the other plate ! do i need a gasket on both sides of the spacer plate or some black gasket meaker will be fine ?thx again to everyone for the help!