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Posted

what would be a safe dome size if im only running pump gas mixing 32:1 on a almost stock engine? 21 or 22 any help will be great thanx.

Posted

I run 20CC domes and just added +4 timing and its a blast. but I run 50/50 mix of 110 race fuel

i actually run 20's, pro circuits, and +5.5 on 95 with stock porting and no deto. pulls hard as hell in the mid. yeilded less power with 100oct.

Posted

i actually run 20's, pro circuits, and +5.5 on 95 with stock porting and no deto. pulls hard as hell in the mid. yeilded less power with 100oct.

 

HUH....when I went from 110 fuel to 93, my friend with the DS650 was able to pull on me by almost 2 full bikes

 

I put in race gas, and we are dead even....have yet to race him with my new timing...my previous timing was -5...dont ask why...I just tore it apart and thats where it was...

Posted (edited)

odd....it must have to do with the timing. when i ran 100, then went down it was after i set it to +5.5, and pulled the mid a bit harder. of course, I'm using av gas, which is formulated to atomize differently

Edited by AKheathen
Posted

Someone forgot to ask you the most important question.

What elevation do you ride at?

 

If you're at a higher elevation, sometimes even a 19 or 20 is fine.

 

Second,

Cranking compression does NOT dictate the need for more octane, compression RATIO does.

NO fuel is rated for cranking compression. It is rated for compression ratio.

Posted

I ride at about 800-1200 ft depends on the area.

 

@Sea level to 600ft i was running 19cc domes on 93 pump with no detonation.......stock port.

Posted

Exactly...every motor and tune is different.

That's why I say check compression ratio.

It's math, you have some measuring to do, but it's not that bad.

I consider it a learning experience as well.

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