Gas for a 13:1?

[KingpinsEx]

Just curious what type of gas a 13.1 compression pistion needs to be run on?

[GPracer2500]

It depends.

In a 400EX?

[KingpinsEx]

No not a 400ex, more of just a general question... But something along the line of todays 450s.

[NacsMXer]

I'd go with a 50/50 mix of 93 and race fuel, if not straight race fuel. I run straight 110 leaded in my 400 with 12.5:1 compression, just cuz it helps me sleep better at night :o

[GPracer2500]

Originally posted by KingpinsEx
No not a 400ex, more of just a general question... But something along the line of todays 450s.

There's no general answer to that question that's worth anything, IMO. There are just too many variables besides static compression ratio that play an important role in an engine's fuel requirements.

That said, I would not run a 450 with a 13:1 piston in the places I ride with the pump gas sold in my region. A typical 450 with a 13:1 piston might be fine on pump gas but only if the circumstances are just right. I know for sure that for me, those circumstances would not be right.

[wes350x]

Dont run pump gas on a 13:1 motor, at least mix with race gas. Found that out with my last bike.

[Benjithx]

Also note that if your bike is jetted for race gas do not try running it on pump because pump fuel is thicker and your bike will run very lean.

This is why people who try running race gas in there pump bikes ofter notice it running very rich.

[Black R/T]

Originally posted by GPracer2500
There's no general answer to that question that's worth anything, IMO. There are just too many variables besides static compression ratio that play an important role in an engine's fuel requirements.

agreed, a STOCK 04-05 honda 450r has 10.5:1 compressioin and it would be ok to run on 92 pump gas. raise that to 13:1 however (without milling, porting,changing cam, timing, etc..) and you would need 100 octane at minimum. put in a radical cam, mill the head, and a little programming and you are now the proud owner of a 7.50 a gallon C12 guzzler.

[ohsobad_chevy]

Originally posted by Black R/T
........ you are now the proud owner of a 7.50 a gallon C12 guzzler.

Where you getting c12 for 7.50/gallon????