what is the most that a new rev box will do for me.. what other sugestions do you have for cheap power

 

I wouldn't get a rev box, I think the best thing for you would be gettin your head ported and pollished. The only thing the rev box will do is of course, rev the engine more, and won't give you much if not any more hp. I think the factory rev limiter is set as high as it needs to be, and any higher would just damage your engine.

 

You are very wrong, Beastly, without a +1000 rpm cdi, it is very hard to get any performance out of engine mods on the 300ex. I put a full exhaust system on my son's 300ex, opened up the air box, added a UNI filter, rejetted, and it ran like crap if you tried to run it hard, it would sputter and hit the rev limit,you could not wind it out in each gear like when it was stock, you had to short shift it, and the top end suffered, you bounced off the limit all the time. Honda has the lowest rev limit of any ATV out there, I have never had this problem with other brands. After putting a White Bros. +1000 cdi on, it was like a different quad, you could run out each gear, it accelerated faster, and you could hold it wide open on the long open spots with no sputter from the rev limit. You could still hit it if you revved the **** out of it, or held it in 1st or 2nd and kept it pinned, but nothing like the stocker. No sense getting better flow in and out if you can't use the extra rpms. Mxjunkie, cheap power for the 300ex is: open the air box, it only pulls air in through 2 frame tubes about the size of a quarter-cost-free. Rejet for extra air flow, jets -about 4 bucks each, do not just put a slip on silencer on,the head pipe is very small,go on eBay and find a good used performance system, then if you have the money,find a +1000rpm cdi, there are guys on eBay that have modded stock ones that remove the limit, DON'T use them, no protection from over rev, and they tend to have starting problems ( I tried one,made it very hard to start, stick with a name brand cdi). Money allowing, go with Beastly's idea of porting the head, that is also a bottleneck,but then you are pulling the head off, replacing gaskets, if you do that, you might as well get a .020 over higher comp piston for more low end grunt and more overall power.

 

thanks 95wolv. I already have jets hmf slip on silencer and a k&n lid removed and i'm getting the slip on pre charger. i'm thinking of a power core from fmf for a header pipe. and i think the 1000 rpm cdi from moose racing or ESR racing looks good. any other brand sugestions for the cdi. what is the usual price to get the cylinder bored out like .020 of .030 over

 

If you take out the jug and bring them the piston to measure, you can usually find a good shop to do it for 60 bucks or so, use a good name brand top end gasket kit, and make sure you have the torque specs for the head and jug bolts. If you are going with a bore/piston and maybe a port job, you should see if you can find the money for a decent cam, it will really make the most of the extra flow and compression, and will make a noticeable bump in power.

 

what do you think that whole set up will cost me total including the $140 cdi box cause that is next on my list then the bore and port job. what do cams run for. thank. oh yeah im 15 so i'm have to beg my mom and still get some cash doing side jobs.. haahaha

 

Weeellllll,
better get a good part time job ! cams run from 150-200, and depending on the type of cam you get, Hondas and some other rocker arm types require hardened rocker arms to prevent wear out from the stiffer valve springs some cams require (another 80-100 bucks) Unless you plan to keep the 300ex for a few years, instead of all the motor work, you could just get the head pipe, rev box, rejet, maybe even regear for more top end,the extra power should let you go up a tooth on the front sprocket (20 bucks for a sprocket). My guess is you will soon be craving more speed, and a Z400 or a 450 would be a heck of a lot faster stock than a modded 300ex. So spend a little now, enjoy one of the best handling trail quads ever made, and work real hard this summer and start saving up for a 400-450 sport quad in the next year or so. But everyone has to do what they feel is right for them, if you really love the 300 (a lot of people do),then there is nothing wrong with modding it to keep riding interesting, a few hundred here and there is easier to do than a few thousand more for a bigger quad !!