Perhaps someone here can provide me some info.

I have used racing fuel on non-modified engines and the effect is none.
Really no power increse, no mechanical failures.

Now, What if you have a High Compression engine that has a modified head for use with high octane fuel?

The question is:
If you use pump gas on this, will you damage the engine?

High compression engines are designed for high octane fuel. Using 91 octane pump gas will cause detonation, and that can cause a piston failure. If you have a high compression motor, you should be using 100 octane at a minimum, and 110 is what I would recommend.

If your compression is high enough to cause the engine to detonate or ping, you will need to run race gas. Race gas will not help out much unless the engine is designed to run on it. Many people claim better throttle response and improved power but on the dyno and in my experience, race gas is wasted on stock engines.

If you ping, you stand a good chance of holing the piston or worse.

One website I read about this issue said detonation from inadequate octane fuel can even bend the connecting rod! OUCH.

Running race gas on a motor that doesn't need it will lower power. Race gas is made to ignite later so it does not predetonate in a high compression motor. This later burn slows the burn process down enough to lose power when you do not need it.

Race gas in a high compression motor is there to prevent predetonation. Rods can bend, pistons and combustion chambers can melt, and spark plugs can be warped.

If you need it, run it. Over the course of a weekend it costs me about 20.00 more to run race gas over regular gas. I buy it by the 55 gallon drum.

the only way race fuel will make you faster on a stock motor is because your wallet will be lighter

Thanks everyone for the inputs.

Last weekend I was riding and using VP. The quad was running excellent after putting a fresh top end.

I ran out of gas and someone bailed me out with some pump gas.
When I got back to camp, the quad was still running. Shut off the engine,but when I tried to crank it again to load the quad on the trailer, well there was no compresion.

It still turns when I crank it, but I can crank it with my hand.
I hope the damage is not so bad.

I also have a question about racing fuel, I was told that you could mix 91 octane with race fuel. A guy at a performance shop said that since it was a quad that it would be OK, does any one have any input??? I have a 87 tecate that has a big bore 300cc and I do not want to damage the engine...

It makes no bearing on whether it's a quad or bike or what. Gasoline engines are simple like that. The simple fact is as long as you get the octane you need for the engine not to detonate, you will be fine. Mixing pump gas and race gas is fine as long as you have enough race gas to get the octane you need. You don't add 91 to 110 (Octanes) and divide by two to get the octane either. You just have to experiment.

I could be wrong but isn't the general rule that anything over 11:1:1 needs something higher than pump gas?

Thanks Fireballsocal but how do I know if the engine is not detonating?? It seems to run fine.....

Run RC Nitro Car fuel!

i-ride: That is not correct any more. With efficient head designs and proper jetting, an engine could have close to 12:1 compression and live on pump gas. Look at todays exotic thumpers. The YZ450F and CRF450 dirtbikes both have compression ratios in the 11.5-11.8 ratio. Due to the extremely effecient head design, these bikes will run on pump premium all day long without pinging.

Suzuki32, it is very hard to hear pinging on a bike unless it is really bad. The best bet is to run what the manufacturer says but if you can't get that information, do a plug check. If you have access to a jewlers loop, use it to inspect the electrode for small bits of aluminum. These bits are actually part of your piston and are causes by pre-detonation.

i have an 05 crf250 with 12.5:1 compression and it runs on pump gas. Alot of new cars have compression in the 11s and they all run pump gas. it is just a matter of what it is designs for.

lol

I've got a question,what compression numbers do you need to run race gas.?

what octane race gas?
10.1 87-91
11.1 91 -100
12.1 100-104
13.5 104-108

im going to a 13.5:1 piston this summer and i cant wait to have to lighten up my wallet w/ some race gas... YAAAAAAAY ( notice the sarchasim ) BUT i do want a bitchen fast bike and i spose you gotta pay to play..

Gots me some headwork coming ( thinking that company that did 24v's head)
Cylinder is getting a makeover ( a company outta illinois )
Suspension is getting a makeover (mx - tech in pheonix )
Frame is getting cleaned up and touched up maybe a new paint job
New subframe (been bent for 3 years time to replace it)
ALLLL new plastics
Bars & Levers
new seat and tank ( yz style )
IF time permits a little bling

and my most favoritist that i cannot wait for... YZF450 CAM w/ autodecomp.. ahhhhhh

Nick, powdercoat that mutha. Don't waste time on paint. Powdercoating will be much more durable, is about the same price, and comes in all the cool colors.

what about the oil in the frame... just worried when they bake it they will get one helluva smoke cloud in the oven..

ISBB...don't forget to save some money for a better, bigger radiator.

you think it would heat up that much w/ just a oversized piston... i honestly dont think its necessary but will do some research on it..