compresion/coolhead help

[jjfizzle51]

hey when do you have to use race gas. like what compresion rate, and if i get a cool head with 19 cc domes being at an elevation about 4500 can i run 84 octain (regular gas) in the shee thanks

oh and i plan on advancing my timing +4 so will that make me have to run a higher octain with that combo

thanks again

Edited June 6, 2005 by jjfizzle51

[jeepman380]

I don't know if i'd run the 84 you might be able to get away with 91. If not run a 5/50 mix.

[switchblade]

I sure wouldn't run 84 octane gas. Run a compression test on to anything over 180 I would run race gas for sure. A few extra buck on gas each hour is better than rebuilding a motor. If race fuel is to rich for your blood just go to a larger cc dome. That is what cool heads were designed for tuneabiliity.

[jjfizzle51]

thanks thats what i thought, how about a 20cc dome could i run the 84 or still be pushing it

[FASTOYS]

thanks thats what i thought,  how about a 20cc dome could i run the 84 or still be pushing it

378274[/snapback]

I would DEFINETLY run premium pump gas in it especially if your bumping the timing! Lots of variables (bore size, altitude, domes, timing , jetting , porting, etc.etc.) when it comes to compression and what gas to run. Normally if jetted correctly i can run prem. pump gas up to about 160-165 lbs of compression WITH a GOOD compression guage like a Snap on . Just my .02

[switchblade]

I would run premium even in a bone stock banshee. I wouldn't chance it for the price.

[Cotton eyed Joe]

hey when do you have to use race gas. like what compresion rate, and if i get a cool head with 19 cc domes being at an elevation about 4500 can i run 84 octain (regular gas) in the shee thanks

oh and i plan on advancing my timing  +4 so will that make me have to run a higher octain with that combo

thanks again

378259[/snapback]

I have a shaved stock head that I'm thinking is around a 20cc dome. I run the high test pump gas with no problems. I haven't dared run anything less. I have the +4 timing advance too. You should be fine with high octane gas.

[aj77ta]

hey when do you have to use race gas. like what compresion rate, and if i get a cool head with 19 cc domes being at an elevation about 4500 can i run 84 octain (regular gas) in the shee thanks

oh and i plan on advancing my timing  +4 so will that make me have to run a higher octain with that combo

thanks again

378259[/snapback]

 

I would run no less than 93 octane in a stock banshee, if u are going to run 19cc domes and advance your timing you had better mix in a little race gas. I run 20cc domes and some advance also and I run a 50/50 mix of 110 and 93 octane. I tried running just 93 octane and had severe detonation to the point that it ate the electrodes off of my spark plugs. Adding race gas fixed that. So I would suggest the same for you. If not you risk severe engine damage. javascript:emoticon('')

smilie

[bansheeryder_69]

I would run  premium even  in a bone stock banshee.  I wouldn't chance it for the price.

378340[/snapback]

Run 1 gallon of 110 with 4 gallons of 91 with your regular oil. It will help your motor if anything.

[80overShee]

Dont ever run lower than octane than what you are graded for by your compression. Even the manual (Clymers anyway) says never run below 90 oct on standard compression. A friend of mine was riding his FRESH rebuilt Shee with me in Leota and blew his head gasket and was pinging like crazy running 87 octane. Literally melted the head gasket. I run 94 on standard compression, just to be safe. If you are too poor to run high octane, you are riding the wrong kinda quad. Banshees LOVE to make a fat wallet thin.

[05bansh]

I have the 19cc's and +4 on the timing. I only ride Sand Mountain. I run 50/50, sometimes 70/30 110 + 91 just to be safe. I rather be safe than sorry. And even if you are running stock I would AWAYS run at least premium pump in your shee.

[sheefreak]

According to a Banshhe compression chart I have, 21cc domes on a fresh top end will put you at 157 psi, 20 cc will put you at 169. Generally over 160-165 most generally run 50/50 mix w/110. If you want to stay w/93 octane(premium pump gas) you should go no smaller than 21cc. You may start running into reliability issues w/your crank if it is stock going smaller than that also.

[Ducman]

jjfizzle51, you keep saying 84 octane but do you really mean 94? I have never heard of 84 octane pump fuel in the US. Most states either have 91 (West coast) and 93 (East coast) for premium pump fuel and 87 is the min octane available. 94 octane premium is available in some cities but rare.

 

Anyway, sice you are running at a higher evation, it would be best if you would measure your compression and use that as a guide to determine your octane. As said previosly 160 psi or less should be fine on premium pump fuel. According to the compression table on the NOSS machine web site if you interpolate to get compression at 4500 ft, 19cc domes should be at 145 psi on a typical stock port motor. At 145 psi you should be fine running 91 or 93 octane even with +3 or 4 ignition advance, but I would measure the compression to make sure you are going to be safe. Also make sure that you know your elevation and don't go riding in an area below 3000ft (which would put you at approx 160psi with 19cc domes), if you do mix in some race fuel 50/50 and you'll be safe. Also make sure you are not jetted lean, if you are at the maximum cylinder pressure which your fuel can support a lean condition can cause detonation. Also remember the cylinder pressure table is for typical conditions, if the air is very very cold and dry cylinder pressure will be higher.

[champ66]

never run regular gas with any 2 stroke youll be boring and replaceing pistens in your shee or chainsaw or any other 2 stroke!

[jjfizzle51]

thanks guys for all the help i think im going to go with the 19 and see if i want to advance the timing. my bad on not running regular this is my first two stroke so i didnt know these things ive been running regular for over a year with no problems but will be sure to run 91 now thanks for saving me a rebuild lol.