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KLX 300 header/exhaust

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Hi, first timer here and just picked up a 06 KLX300. I've been looking at the mods to do because the bike just seems to lack throttle response. After reading the forum, I'm also going to remove the airbox cover, get the 49 state jet and ordered the 44 springs ford the fork.

I'v read that leaving on the stock muffler and adding a header is the best way to go for better performance. Has anyone done this with better results than adding an exhaust pipe? thanks

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I just recently got a 07 klx300. I haven't done any mods myself but the previous owner cut the airbox from what I believe (haven't actually looked at what he did yet) and rejetted it.

One thing you can try is to take off the end piece from the tailpipe. It opens it up a little and so you get some more power (I heard that you gain 4HP but I can't image that's possible with just taking that off) and you still have the spark arrestor. I've heard that you can keep the stock slip on pipe, and just get a new header from fourstrokeworks. When you take off that tailpiece, the only thing that is limiting airflow is the header.

You could also put a pumper carb on, but I believe those are pretty expensive. Those really unleash the bike, from what I have heard.

http://www.planetklx.org/ is a great site where you can find all the mods and things you can do with these bikes.

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Zack,

Thanks for the info and I have seen the sight Planetklx. I just wanted to know if anyone found that by adding just the header would do the trick or if an aftermarket pipe was better...rejetting and changing the fork springs this week.

I took off the restricter plate experimenting and it ran like crap, way to lean. Once the jet is changed I'm hoping everying will be much quicker.

thanks for the reply

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If you only have the desire or funds to replace one of the items then getting the header pipe and removing the butt plug from the stock exhaust would give you the best bang for the buck. Go to Planet klx and do all the free mods listed or you care to perform. You will get additional benefit from these upgrades and they do not cost much if any cash outlay at all. A JD jet kit would be of great benefit to the performance of your machine and it is not all that expensive.

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A JD jet kit would be of great benefit to the performance of your machine and it is not all that expensive.

Is JD making a jet kit for these bikes now? Or did you mean the Dyno-Jet kit?

Ride on

Brewster

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If you only have the desire or funds to replace one of the items then getting the header pipe and removing the butt plug from the stock exhaust would give you the best bang for the buck. Go to Planet klx and do all the free mods listed or you care to perform. You will get additional benefit from these upgrades and they do not cost much if any cash outlay at all. A JD jet kit would be of great benefit to the performance of your machine and it is not all that expensive.

100% exactly what you should do. don't buy a silencer just to make it look pretty like some folks do. an oversize header is where its at.

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Zack,

Thanks for the info and I have seen the sight Planetklx. I just wanted to know if anyone found that by adding just the header would do the trick or if an aftermarket pipe was better...rejetting and changing the fork springs this week.

I took off the restricter plate experimenting and it ran like crap, way to lean. Once the jet is changed I'm hoping everying will be much quicker.

thanks for the reply

You twice mentioned the "jet".

You do mean the 49 state needle, don't you?

This is not to say it doesn't need rejetting, of course. And don't forget to remove the plug over the mixture screw it it's there.

A better ideas, as others have said, is to get the Dynojet kit. It includes their own needle and an assortment of jets.

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:thumbsup:I have a 2004 klx300 and did all the free mods to it as seen in planet klx and was very pleased but wanting more I put a dyna jet kit in the carb,moose air filter and a complete Big Gun exhaust header included. The increase in power with the free mods were good but when I added the other it was like a whole new machine. If you don't want to spend money on exhuast I would suggest the dynojet kit. What I understand is that by just adding a Fourstokesworks header and leaving the stock muffler is about as good as you can but I got a really good deal on the big gun off of ebay. The Klx is a very easy bike to hop up at a very reasonable price and by doing a little research on this forum will be helpful .

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Hello Everyone,

Thank you for all your comments. Here is what I have done so far with some great results: Changed the needle to the 49 state one from the California smog one and one of the jets. Removed the exhaust plug and opened the air box. What a difference!!! Now I have throttle response. After reading all the posts I'm wondering if I should have purchased the Dyno jet kit...not sure if it would make that much difference.? Does anyone or has anyone put on a header without the dyno jet kit and have it workout okay?

Oh ya, I put new fork springs 44 and it definately helps the nose dive but the oil that was in there was very thick...i will be changing that soon.

Thanks again,

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Just to let you know that the increase in power with the dynojet kit and the Big Gun full exhaust did give it more power. I could lift the front wheel pretty decent before with just the free mods but when I went with the dynajet kit and exhaust it,s like a not even having to think about just whack the throttle and you have it in the air but low speeds in snotty conditions it is very tractable. I went this was because it was cheaper maybe some day I will spring for the carb swap but right now I.m very pleased with the bag for the buck I got. I hope you did the crankcase breather hose mod also. If you do think you want to swap carb search the intake forum as they have some good info on mikuni tm carbs and kehin fcrs. Happy riding!

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The first item I put on my bike back in 99 was an exhaust system. I to did the free mods listed on Planet KLX. About four years ago I add the header pipe from Four Stroke Works. Big improvement in performance. Last year I put in a Dyno Jet Kit. Once again the improvement was impressive. I also cut 3 coils from the vacuum spring. You definitely get your moneys worth with this install. I hihhly recommend it.

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