300ex performance

[mpbond]

Hi, I'm new to the board. I have a 98 300ex that I have had for 6 years. I finally got back on it after about 2 years and I am now able to do more riding and I want to up the power some.

It already has a K&N filter and 4 1in. holes cut in the airbox. First, what would be a good jet size for this setup.

Second, what are some of the cheaper performance mods to get some more power. I will get an exhaust, but it will be later this fall.

Any help would be appreciated.

[Mx_523]

What kind of riding do you do? Whats your budget? And, where exactly did you put the four 1inch holes in your air box?
Just run the K and N with a outwear and no air box lid. For an exhaust the best is the Curtis Sparks X-4 and it cost 350 dollars I believe. Hmf makes good pipes for the 300ex too. I wouldn't go to far with the mods for a 300ex because you will be wanting more power soon. Just my opinion.

[mpbond]

I mainly ride trails with some places where you can really open up. I don't really do jumps anymore. My budget is whatever I want. If I want something, I will get it. I'm 27 not a kid. I don't really have a set budget.

I haven't done anything to the bike. It was like this when I bought it. The holes are in the top of the airbox lid.

I would like to do a good amount of work to the bike. I don't ride enough to get a new one and I don't race. So a bigger bike isn't neccessary. I spend most of my money on my cars and I build 600-700hp turbocharged engines for a living, so mechanical work is no problem.

[Mx_523]

Well we can start with suspension, I would go with +1 arms (burgand) and Elka res shocks. A raptor 01 rear shock.
With the engine, you can get a 330 kit from FST (www.fourstroketech.net) and have a web cam to that. You can get a web cam from Magic Racing (www.magicracing.com). For the exhaust, I perfor the Curtis Sparks X-4 exhaust. But it is very loud. You can get a quiet core for it also. You can buy the pipe from Curtis Sparks Racing (www.sparksracing.com ). As for the tires, I would go with either Kendra Klaws (sp?) 22"s or Maxxis Razr 22" both rear and front. You can get them from Rocky Mountain Atv (www.rockymountainatv.com).

Hope this helps a bit.

[Sjorge450R]

^^^^ I will have to disagree. Dont get 22" tires all the way around. BAD choice. go for 22" fronts and 20" rears. With the raptor rear and the 22" the rear end will sit SOOO high. Take this from a racer that has raced with 22" rears. I will NEVER do that again.

Also, if I were you, I would do a 330 kit and compliment it with a matching cam/valves/springs. Most of a 330 kit you can do yourself expect for the sleeve instalation. Also, dont forget an oil cooler.

Exhaust pipes on quads is a very touchy subject. Everyone has their own opions on what is the best, but most people have only used one exhaust on their quad. I really dont understand why a a lot of people say what they have on their quad is the best, does it really matter? Any of the higher end pipes will be good. I myself run a Supertrapp and I believe I am the only one on here that uses it, but let me tell you it works. I have won 2 races and am ranked 1st in D-6. That is against some 300ex's that have a Sparks Pipe. Just go with what ever you want: Sparks,HMF,HMF/WB combo,Supertapp,pro-circuit.

Any more questions just ask.
Stevee

[bwamos]

I will agree with most of what's bee said here.

First get the exhaust. Sparks X-4 is also my reccomendation for the 300ex.

I've also ran a K&N on my 98 ex with a prefilter and no lid for years without any issues. I'm playing in the same Missouri muck you are.

Next in the performance market.. get a Cam, and perhaps an 11:1 piston. Beyond that.. don't waste your money. If you want more than that get a 400ex. ;) It will be cheaper.

Outside of engine work.. the shocks on the 300ex can use an upgrade. There's a lot of different options out there.

[mpbond]

I think I have decided on the HMF/WB combo. It sounds like the Sparks is going to be too loud for me. I am also looking for a 400ex carb.

I am also going with a cam and eventually a higher comp. piston(11:1).

I have been hearing about a new CDI box for more RPMs. How high can these things rev before they come apart? I don't know if it will be neccessary to turn that much more RPMs.

Also, I just found out about adjusting the valves. I haven't done it since I owned it, and I don't think it was ever done before. I was told that it will give me a noticable increase over what I have now. I bought a Clymer manual, so I will be doing some adjusting and tuning this weekend.

I ordered a prefilter and will be removing the airbox lid when it comes in.

Thanks for all the advice. Keep it coming, it is much appreciated.

Mark

[300exOH]

Originally posted by mpbond

I have been hearing about a new CDI box for more RPMs. How high can these things rev before they come apart? I don't know if it will be neccessary to turn that much more RPMs.


The CDI will only raise the rev limit about 1000 RPM's. It shouldn't hurt anything at all.

I doubt you will notice much performance gain from adjusting the valves unless they are way out of adjustment but it is still a good idea. When you adjust the valves it helps to bend the end of the feeler guage about 45 degrees. It will make it easier to get the guage under the rocker.

The best upgrade you can do on the 300ex is shocks. Good suspension will allow you to ride the quad faster than engine mods. The power isn't worth much if you can't get the power to the ground.

[mpbond]

My main problem w/ getting the power down is that my holeshots only have about 3/4 in of tread left. They were on the bike when I bought it and I never changed them.

I want more power. I here of guys doing wheelies in 3rd fairly easily. I can't get it up in 3rd even if I peg the limiter and dump the clutch.

I do think that my valves are way out of adjustment and I don't think that the carb was ever tuned.

[300exOH]

Tires do make a big difference. I really like the kenda knarly's on my 300.

Get the carb jetted/adjusted right and you'll be surprised what a difference it makes.

[bwamos]

I agree.

The sparks is pretty loud... but he does have quite cores for the newer model.

You'll like the HMF/WB combo.

Valves should be adjusted to .004 clearance intake and exhaust. You need the clearance for expansion.

Jetting will help a lot and you will feel a big difference with the new pipe/silencer combo.

Increasing the rev limit on the 300ex is a great improvement also. You can get the rev limit increased on your stock CDI. I cant remember, but I beleive the stock rev limit is either 7200rpm or 7600rpm. Either way it is really really low. +1000rpm won't hurt a thing. The 300ex can run at 8600 without issue. I run mine up near 9500 rpm's on a regular basis and I've got a larger bore, higher compression and a much more agressive cam.

I also agree that suspension is paramount for the 300ex. Beyone the simple pipe/filter/cam combo you want suspension.

[mpbond]

How do I raise the limiter on the stock CDI? If anyone knows the parts I need to change, I can do it myself. I work on circuit boards fairly often too.

[humblesquirel21]

i would recomend a cam after suspension work it makes a big difference since your quad is older make sure you look at the valves to make sure they are sound mine wore out and on droped needless to say catostrophic engine damage

hope fully mickey dunlap can help me out (hes one of the best around for engine work ) he has al kinds of kits for the 300 depending on how far you wana go btw