mikstr

What fuel do you run your bikes on? Will 91 octane do the trick? Also, are you running stock or aftermarket cams and does this affect your octane requirements?

thanks in advance

killer5280

93 octane with JE pistons and stock cams. I haven't tried 91, to be honest, but I did accidentally fill up with regular once and the thing would hardly run.

mikstr

thanks

I recall reading that more aggressive cams help to reduce cylinder pressure a bit so maybe 91 would do teh trick. I ask as some gas stations here in Canada only carry 91 as their premium and I wouldn't want to grenade the engine as a result of using it. It looks like I may have to find a way of upping compression by some other means than the JE method (milling the head, custom pistons,....)

gboezio

Petro Canada have 94 octane on their big gas stations, it's expensive stuff tough.

mikstr

yes, and I am led to beleive that the additive in their gas (ethanol?) attacks the diaphragm in the fuel petcock too, drastically shortening its life (I know, I've had to replace two of them already).....

gboezio

uh Ethanol eats the petcock ?? Damn that's what I'm using on my bike, I'm fueling at the CO-OP these days.
Volumetric Efficiency is directly affected by compression. A compression increase will definitely wake the bike up, it will increase gas mileage, horsepower, response. The stock compression is so low that it's totally useless to use premium gas on the stock form, I fueled my bike with regular gas without a hint of detonation even on lean operating condition.

If you raise the compression, get a larger main jet and back the needle more, it will chill the combustion a tad. Whatever is done make sure the squish aera is unchanged, this is the key for fast combustion and detonation avoidance. This is the clearance between the piston top and the head that induce turbulences in the chamber to spread the flame front. Specially avoid high compression pistons and a thicker head gasket to back it up a bit, it will ping like a piano.

If you need higher octane fuel, you can blend plane fuel to 91 octane 1:4 if you get trouble (I haven't tried yet).

vtr1000

Sunoco has 94 octane too!!

mikstr

Sunoco definitely has ethanol. While it does have certain advantages (keeps insides clean, for example), it attacks the rubber membrane in the petcock (albeit not over night)

jamesvtr

i just run premium where ever i go no problems i a couple of years