Race Fuel?

[nshalaby]

hey guys, ive been looking for a RN SJ now for awhile, and more specifcally one made for freestyle and close to me. I found one, however, the owner says that it has a 735cc motor thats been ported/polished by balance racing and that it needs 110 octane fuel. He says it also will run off 97, but i heard that when you run high octane fuel they are alot more to maintain and its hard on all the rings and seals...other than that it seems like a nice ski...ill have to do a little work to convert to a freestyle, but just wanted to ask the pros! thanks

 

[yankeeboy]

I just started running race fuel, and i'll have to say its not fun. If you can find it locally its not as bad ( besides the price). The pros vs cons though i have yet to see anything good about it.

 

[restosud]

race fuel is nice but gets expensive quickly.
you may be able to detune it enough to run pump gas however?

 

[Freakrider]

find out if the head has removable domes so you can bring the compression down to run 91-93 pump gas...or bring it down some and blend avgas with pump gas....u have several options...

 

[Matt_E]

If the engine was built to run with 110 octane gas, then detuning it to run with pump gas will be very detrimental to performance.
I am guessing that the exhaust ports are high and the bottom end is made up with high compression.
Run lower compression and the bottom end will be gone.

 

[Don 79 TA]

I myself have been using race gas for years
quiet honestly never had a problem, and i run some strong PSI, not to "make more power" but for that crispy throttle feeling and strong wind up. I don't ride W.O.T.

does it require more maintenance, well yes and no...
the psi will put more stress and pressure on the rings, crank, etc...
but it also depends how the motor is setup overall, what oil you use, how much riding you do, etc.

the pros... there are alot to list... same for cons...
to me the con was getting the fuel and the price... however when gas was almost $5 and race gas was $6... didn't matter to me

race gas is also a much better quality fuel. to me it depends on your preference and riding style, and of course $$ and availability of fuel...

I have also ridden pump gas setups that were faster then mine, but their initial build cost is more $$ in the porting and what not...

if you are interested in it, make sure you do a compression test in both cylinders, and see what race gas costs in your area. you can swap domes, but as Matt said, you don't know what effect it could have.

don't forget the other pro....
the smell... although quiet honestly i can't smell it.

 

[nshalaby]

alright thanks alot for the input. the head on it is just a stock milled. I dont mind paying for the race fuel, but the owner did say that the engine was built in 05 and has been running since. Should the rings, seals, and gaskets be checked after that amount of time or should it be alright?

 

[Don 79 TA]

really all depends on how much time has been on it, what was initial compression reading, how is it now (even both cyl's) and after a ride how does it feel to you?

never hurts to have a tear doown done to double check things, and replace rings.

 

[nshalaby]

yea he said that compression was 175psi, but that was last year, so im guessing he just hasnt fired it up yet this year. I was thinking if i do purchase would it be wise to get new rings and seals, and maybe a port and polish job?

 

[Matt_E]

Porting isn't something that's done on a regular basis.
It is a one-time mod.

 

[Etheraldreamer]

yea he said that compression was 175psi, but that was last year, so im guessing he just hasnt fired it up yet this year. I was thinking if i do purchase would it be wise to get new rings and seals, and maybe a port and polish job?

175? if thats true and thats what its supposed to be, you are fine with pump gas.
most of us run pump gas up to about 185-190.

 

[Matt_E]

175? if thats true and thats what its supposed to be, you are fine with pump gas.
most of us run pump gas up to about 185-190.

I would talk to the builder of the engine to find out why race gas was recommended. Porting and ignition timing may still require the OP to run race gas.

 

[SurferSmurf]

i have a 771cc motor built by pro tec and it was an ex-racers ski. i was told to run 105 octane then i checked out the motor it has race porting and the compresion is only 160. i started running on 93 octane and never noticed a differance in power or opperation. the only differance i noticed is that my wallet is fatter and my ski does not smell as good without the race fuel.