racing a 300

[cr977]

i have a stock 300ex and it is in pretty good shape. i used to ride quads many years ago and got a dirt bike, i have been riding dirt bikes for like 4 years and i switched to quads 2 months ago and i am already riding my 300ex to just about its full potential. i am on a budget so i am going to keep the 300 just mod it, i dont know the racing classes so i would need to know, i am 15 turning 16 pretty soon so that may be some good info. i am going to put the basic mods on the bike, plus i am going to bore it out could someone give me some tips?

[SET THE STAGE]

before anything, get a pipe. stock 300 pipes are VERY restrictive. curtis sparks are wonderful and not too expensive compared to other companies.

[300exOH]

Suspension...even a used set of works shocks would do the trick. The stock shocks are horrible on the 300 and it is very easy to push them to the limit.

Also like set the stage said... a good pipe and proper jetting really wakes up the 300. Just stay away from cobra and the low end DG pipes. FMF, HMF, Sparks, DMC alien and even the high end DG pipes will help. I have the sparks x4 and it made a HUGE difference from stock. Just make sure you go with a full system and not a slip on. The stock header is very restrictive even on a stock motor and it would really hold back a modded engine.

What type of racing are you planning? XC, MX, etc...?

[cr977]

Originally posted by 300exOH
Suspension...even a used set of works shocks would do the trick. The stock shocks are horrible on the 300 and it is very easy to push them to the limit.

Also like set the stage said... a good pipe and proper jetting really wakes up the 300. Just stay away from cobra and the low end DG pipes. FMF, HMF, Sparks, DMC alien and even the high end DG pipes will help. I have the sparks x4 and it made a HUGE difference from stock. Just make sure you go with a full system and not a slip on. The stock header is very restrictive even on a stock motor and it would really hold back a modded engine.

What type of racing are you planning? XC, MX, etc...?

xc, my problem is i only found one 350under class and it went from 9-15, im out of that pretty soon, so i dont want to bore it out unless there is a class for under 350 where somone over 15 can ride. if there is not such a class i have a 390 kit waiting on me for a little money, that should be enough to run with c class 450s. right now, i just got some mods for it for cheap, a 350x swingarm and shock, a 14t sprocket, hub extenders(temporary i am running an atv rodeo this weekend) i got rid of the light and put new lights up there, i took off the reverse lever, cable, and the parking brake cable, in favor of just a clutch cable. and i am taking off the start, high low, control panel thing in favor of a starter and a new light switch those are my mods so far, and i have new plastics from an older 300. that is it for mods so far. alright i got to start somewhere with mods, i guess pipe is first, what is the best pipe i can get for a reasonable price? and what filter should i look at? i already have a 400ex carb with choke out, it is not on bike though. as you can tell i am getting rid of all the junk in order to ditch weight and give it a more simple race type feel.

[Justin#38]

Originally posted by 300exOH
Suspension...even a used set of works shocks would do the trick. The stock shocks are horrible on the 300 and it is very easy to push them to the limit.



yes but only the front ones suck the rear is fine stock

[300exOH]

Originally posted by cr977
xc, my problem is i only found one 350under class and it went from 9-15, im out of that pretty soon, so i dont want to bore it out unless there is a class for under 350 where somone over 15 can ride. if there is not such a class i have a 390 kit waiting on me for a little money, that should be enough to run with c class 450s. right now, i just got some mods for it for cheap, a 350x swingarm and shock, a 14t sprocket, hub extenders(temporary i am running an atv rodeo this weekend) i got rid of the light and put new lights up there, i took off the reverse lever, cable, and the parking brake cable, in favor of just a clutch cable. and i am taking off the start, high low, control panel thing in favor of a starter and a new light switch those are my mods so far, and i have new plastics from an older 300. that is it for mods so far. alright i got to start somewhere with mods, i guess pipe is first, what is the best pipe i can get for a reasonable price? and what filter should i look at? i already have a 400ex carb with choke out, it is not on bike though. as you can tell i am getting rid of all the junk in order to ditch weight and give it a more simple race type feel.

Sounds like a good start. I'm not sure if the 350x shock is rebuildable but you may want to look into it to get the most out of the setup..especially since it is a 20+ year old shock. Pipe is a matter of preference. If you are on a budget the supertrapp pipe is probably the best bang for the buck. It's almost identical to the sparks at nearly 1/2 the price. Sparks would be about the best you can get but it isn't cheap( around $450). I prefer the UNI filters but the K&N works well also. I'm not sure you'll need the 400ex carb unless you have some major engine work. The stock 300ex carb works quite well on a stock/lightly modded engine. Also opening up the airbox lid will help it breathe a bit better. I used a outerware airbox cover to cover the cutout in the lid to keep out mud/dust.

Here's a pic of my lid just to give you an idea...

[300exOH]

Originally posted by Justin#38
yes but only the front ones suck the rear is fine stock

I thought that until I switched to an aftermarket rear shock...the difference is night and day. If I had to only replace one it would be the fronts though. The stock rear shock is okay but I wouldn't want to race with it.

[cr977]

this probably isnt the most original idea but as a poor mans big bore kit, could i slap a 350x jug and piston? how would it mount up? and what is the actual displacement of the 350x?

[SET THE STAGE]

Originally posted by cr977
this probably isnt the most original idea but as a poor mans big bore kit, could i slap a 350x jug and piston? how would it mount up? and what is the actual displacement of the 350x?

i've heard of it being done, but i don't know exactly how.

doing that would also mean you would need to either make a custom exhaust or buy a 350x header

[300exOH]

Originally posted by cr977
this probably isnt the most original idea but as a poor mans big bore kit, could i slap a 350x jug and piston? how would it mount up? and what is the actual displacement of the 350x?

It may require some machining to make it fit but I'm not positive about that. I believe I read that the jug/head are slightly taller than the stocker and would hit the upper part of the frame. Plus as already stated you would need some custom exhaust work. After all that I'm not sure it would be any cheaper than just buying a big bore kit meant for the 300ex.