what fuel or fuel mixture do you use?

[DriftRacer B]

I'm building an Azusa minibike with a Powerfist 208cc, which I call the Canadian Predator clone. I'm leaving the governor in, but using the longer hotter plug for more compression, size 34 carb jet, heavy duty valve springs and have a Gokartsusa exhaust pipe and muffler. I'm planning on running 91 octane, ethanol free gas because I know how ethanol screws up engines, especially 4 stroke motors like these.

I'm just wondering if anyone else feels the same, or are people just running 87 octane with 10% ethanol? I work in the fuel refining industry and know this subject very well and wouldn't use 87 octane in my car so I wouldn't put it in a new minibike engine. I'm also going to be adding a small amount of fuel additive/cleaner/lubricant and octane booster usually used in NHRA Pro Stock racing, which will get the octane up to about 93-94 points.

I'm new to this hobby so I'm curious if anyone is running customs fuels or anything. I run 91 octane, zero ethanol fuel in my car with the additive/booster and in summer, I mix 8-10 ounces of 100 octane racing fuel so I'm used to mixing up my own blends for specific purposes.

 

[creia]

For the engine you have described, you are wasting your $$ on 91 octane- absolutely no need for that. We have been using regular unleaded pump gas 87 octane for years in our bikes w/o a single problem. We DO ,however, always use "Sta-Bil" brand fuel stabilizer, which keeps the gas from going bad. We add 2 ounces to our 2 1/2 gallon fuel container every time we fill it up. A little bit goes a long ways and is very inexpensive.
Michael

 

[minikenny]

You should do what makes you happy. :thumbsup:

A spark plug is not going to change the compression ratio. 87 octane is plenty for these engines in stock form.

If you aren't running 5000+ rpms you don't want or need heavier valve springs either.

Improper storage with fuel in a vented system screws up engines, whether it has ethanol in it or not. In my opinion.

 

[DriftRacer B]

Thanks for the information! I will forget changing the valve springs. I was thinking that was overkill w/o removing the governor anyway, glad to have confirmation. Ok, being new to this, I am only quoting what Gokartsusa.com says about the plug I purchased. They said because it was longer and had hotter spark, it increased compression a bit. my mistake, I'm new to 4 stroke engines and learning my way around them by taking apart the engine myself and changing out the parts I want to replace.

However, regarding the fuel, I appreciate your information and we are doing sort of the same thing. I am using ethanol free gas and the additive that I am using is also a fuel stabilizer for the same reasons. But, the reason I won't use 87 with ethanol is not just the gumming up of the engine as the fuel separates, but also because 87 octane with ethanol is also known for carbon deposit buildup, especially in direct injection engines, but can also cause similar problems in carbureted engines as well.

Where I live, gas is cheap because its refined about 10 minutes away from my house. 91 is only a few cents more than 87 octane, so price isn't really an issue.

If you want a really good fuel stabilizer, lubricant and fuel system cleaner, that also boosts octane a point or two, try Muscle Products, Fuel Treatment, FT-10. a 16oz bottle, will treat 160 gallons of fuel and will make the engine run amazingly well. Its a good stabilizer, I have added it to 5 gallon cans of 100 octane racing fuel and its still good almost 8 months later. No separation. If you have a full size motorcycle, it will make it run like a scared rabbit on steroids.

thanks again for all the input. I really appreciate the help.
Cheers

 

[bigrob]

I tend to use a mix of gas from the lawnmower jug or left over mixed outboard gas or last winters snowblower gas
It really doesn't seem to make much difference lol