fuel octane question

[ARMY_rider]

When is it necessary to upgrade from pump fuel (91) to like 110? Right now I run half 91 and half 110. Is this necessary and why?

[trx250rider]

first you need to do a compression test, after you know that post it and we should be able to help you decide on what octane should be used..do you know what size dome you have in your cool head?

[ARMY_rider]

how do I do a compression test and what do I need to do it? and no I don't know the size. I just bought this not too long ago and haven't had a chance to take it all apart and really check. Is there a easy way to tell?

[trx310R#24]

go to autozone an ask for a compression tester...

[trx250rider]

you can barrow one from autozone for about 35$..when you bring it back, you'll get your money back...if you take your head off the cylinder you can look at the bottom side of the head...there will be a number like 19,20,21,22..the lower the number, the more compression you'll have..hope this helps

[wilkin250r]

People often mistake "octane" as meaning "power". It does not. More octane will not give you any increase.

However, if you compress your mixture more before you ignite it, you WILL get more power. But that's easier said than done, normal gasoline can only handle so much compression before you get problems (it will ignite on it's own, before the spark plug fires).

This is where octane comes in. It's not a measurement of power, but rather a more like a measurement of stability. Higher octane can handle higher compression. THIS is where the power increase comes in, from the higher compression. But you need a higher octane fuel to handle it.

This is just a general guideline, there is more to fuel than just octane rating, but it gives you the background info. You need higher octane whenever you have a higher compression ratio, which you probably DO if you have a Cool-head.

If you go to any automotive store, they will have a compression tester, and can walk you through the basic steps.