20cc domes

[87_shee]

I just ordered a set of 20s for my coolhead, I know I will find out whether or not I need to run higher octane once i check my compression, but I was just curious as to what you guys think.

my elevation is around 0-500 ft

I have about 130lbs with 22cc domes, so what should i expect with 20cc domes?

I also have an adjustable timing plate set at +4

[Wildcard2]

you will see around 16lbs to 20lbs going down to sizes in domes. Quick question though that compression seems kinda low for your altitude. Do you have pretty aggresive porting done?

[87_shee]

you will see around 16lbs to 20lbs going down to sizes in domes. Quick question though that compression seems kinda low for your altitude. Do you have pretty aggresive porting done?

 

No I have just a clean up port, but the motor is getting a bit tired so its probably lower than it should be. Its getting a new top end and welded crank at the same time as the new domes.

So i should expect to see a 32-40lbs increase when goin down 2 sizes right?

[Wildcard2]

yes thats low and you were ahead of me on needing the top end :happy: So yeah you should see right around that much diffrence in the compression.

[dragbanshee]

I just ordered a set of 20s for my coolhead, I know I will find out whether or not I need to run higher octane once i check my compression, but I was just curious as to what you guys think.

my elevation is around 0-500 ft

I have about 130lbs with 22cc domes, so what should i expect with 20cc domes?

I also have an adjustable timing plate set at +4

 

Yea I'd say 160-165

[87_shee]

So should i be safe to run premium pump gas or should i have to switch to race gas, asuming that i will have around 160lbs. I think that it will probably be borderline? what do you think?

I dont mind running race gas for a while, but i will probaly just get some 21cc after a while cause all i can get around here is VP and its pretty expensive.

[dragbanshee]

So should i be safe to run premium pump gas or should i have to switch to race gas, asuming that i will have around 160lbs. I think that it will probably be borderline? what do you think?

I dont mind running race gas for a while, but i will probaly just get some 21cc after a while cause all i can get around here is VP and its pretty expensive.

 

You have your timing set to +4 also so I think your going to have to go with some type of race fuel, I think your going to be on the high side of 160+ psi.

[87_shee]

You have your timing set to +4 also so I think your going to have to go with some type of race fuel, I think your going to be on the high side of 160+ psi.

If I backed my timing off do you think i would still need the race gas?

[dragbanshee]

If I backed my timing off do you think i would still need the race gas?

 

I would wait and check comp. and then decide, cause you were putting them on regardless. Kinda defeating some of the purpose for the domes/timing increase. You might get lucky, no not your old lady! your bike. :shrug:

[87_shee]

Yah you make a good point. I'll just pick up some race gas and leave my timing where it is now.

I have never used any higher octane gas before so what would be the right stuff to buy. I think i can only get VP around here but I looked on their website and theres a bunch of different kinds, I want to make sure i get the right stuff. Do you need certain oil too? I currently use Lucas semi synthetic, can i continue to use this?

Sorry for so many questions, but I appreciate the help

[Thewhite]

Personally I have no problem to run a set of 20cc dome with +4 deg of timing with 94 octane pump gas. My compression go up to 158-160 psi with a rush of crank stroke (like 15 to 20 stroke). My elevation is 0-500' (I ride normally at 100' of elev) near Montreal, Qu

[dragbanshee]

Yea I wasn't sure on the fuel I know I cant get anything over 93 around here.

 

You can use what ever oil you have been.