cdi or coil upgrade

[300_dude]

Somebody told me that if I have a stock engine with aftermarket exhaust and precharged k&n filter and airbox lid off I should not put the aftermarket coil or the cdi box. Or if I do I need to upgrade octane to prevent detonation. Is that true? If so, what kind of octane do I need?

another thing is that I have on my 300ex (2001) the factory front sprocket (13t) and the rear one(38) both stock. All I do is ride in trails almost all the time. I was thinking about going with a 39tooth in the back and leave the 13 tooth in the front. Shouldn't that give me more acceleration? If I put the aftermarket coil and cdi box that should give me some more rpm too. So to conclude I was asking if I put a 39tooth in the back with the 13tooth in the front and if I can put the coil and cdi box will it be ok for me to ride around in the trails without a problem? I also have a 12tooth front sprocket but did not know if it was better 12t and 38t or 12t and 39t or 13t and 39t. thanks a lot. all answers will be really appreciated.

[honda300EXtreme]

no i dont agree because you only have to increase your octane to prevent detonation usually with a higher compression piston or engine mods, if you do either get the cdi box because that just allows more rpms before the rev limiter kicks in- does not require a change in gas ;)

with the 300- bigger sprockets will give you better acceleration but less top end, im up 1 tooth also and its alot better for trails and hills, and yes even with that gearing you can put a after market cdi box on,

* remember goin down 1 in the front is like goin up 2 in the rear*

if it was me i would run 12, 39 for best acceleration and it will run alot better on the hills

[300_dude]

thanks a lot I will keep all that in mind.

Does anybody knows what is the difference between a MONSTER COIL and a REV BOX? can you install both at the same time in your atv? do they do exactly the same? thanks a lot . all replies will be well appreciated.

[250X_project]

True, the CDI does not need higher octane. It just gives you more R's, that's true... But I believe in some cases the coil would need higher octane because it changes the ignition curve and intensity (do not quote me).

Also front and rear sprocket size changes are COMPLETLY OPPOSITE. Bigger in front is the same as smaller in rear, and vise verse. Bigger front/smaller rear gives better top speed, but less low end acceleration. Smaller front/bigger rear gives better accelerating power and LESS top speed. It is a trade off, you decide which is more important to you and your riding style.

Also the 1 front tooth = 2 rear tooth fact is interesting, I've never heard that.

So no the 2 do not do the same thing... and yes you could use both. And IMO I would never change the rear sprocket, unless it is worn and needs to be changed(which of coarse is easier and cheaper than a case replacement). It is all the same work as changing the front...and then some. ;)

JUST MY 2 CENTS...:D

[300_dude]

thanks a lot and I will keep that in mind. very good to know.

[suzukiray]

Actually, going one smaller in the front is like going THREE bigger in the rear. That, in most cases where you don't need ABSOLUTE top speed, usually works out the best. Ray.

[honda300EXtreme]

yea ive heard the 3 tooth increase also, but what were mainly saying is do your gearing up front

[250X_project]

Actually I did the math and it is 3 teeth. 1 tooth down in front is actually just a tiny bit lower geared than 3 up in the rear. (3.16 vs. 3.15) If you want to go down enough in front that you want as small as an 11T I can give you a site, if you don't find any that low.

2.92 is stock gearing
3.82 is lowest possible
2.40 is highest able (w/ parts I, personally can find)

Just some info to through out there...