So I bought my bike last summer and LOVE it but like a lot of people I want more. So my questions are....

Will the 351 Big Bore kit work on my bike? Can I use the stock carb with the 351 kit if I rejet it? Will the IMS 04 KLX 400 E/S 4.0 Gallon fit my bike and if so will I have to make any mods to get the tank to fit?

I'm just looking for a little reasurance befor I jump

 

I go against the grain when it comes to adding the 351cc kit, at least until it's time to rebuild. I dunno if my 09 just runs better than others or what, but even stock it surprised me. But I hated the sound of the stock pipe so the mods began, and with this heat here, probably wont be finished until the winter time.

Have you added an aftermarket pipe yet? Try a slip on like the FMF Q4. The sound is so much better and it added a little bottom and mid range on mine even with the stock jetting, gearing and airbox. In fact, I think it was still jetted good!

Phase two was to pull the airbox lid and add the FMF Mega Bomb header pipe. I wish I would of bought the Power Bomb insted of the MB because it sticks out to far and burns your pants. But with those mods, I am definitly running too lean now. I have the DJ jetting kit but it's just to feeking hot to work on my bike in a parking lot.

Before you start ripping apart a perfectly good engine, do the slip on exhaust, air box mod of your choice, the DJ kit and gear down 1 up front and try that.

Welcome to the forum!

 

The 351 is the best mod I have done to my bike. BUT it doesn't hurt to start with some of the other stuff first you will need most of them if you go with the 351 anyway. Maybe the smaller improvements the pipe and jetting gives you will be enough, or satisfy you while you save up for the 351.
The 351 will fit your bike.
You can use the stock carb, (I still do and it's fine)
I don't think that tank will fit.
congrats on the bike
Dan

 

Yeah, I agree with Dan. My KLX had every common mod of a full Muzzy exhaust, DJ rejet, all airbox mods, and de-smog when it was a 250. The engine performance was much improved. The biggest notice when going to just a 300 OEM cylinder/piston was bottomend increase. I still had to wring out the 250 pretty well to really get it going, but just the addition of the 300 jug gave some very noticeable increase down low with much better short shifting and lugging power. It still sings in the higher rpm range which is a nice feature in many instances. Not surprising, I guess, when you consider that I believe the '06 and later engines to really be more akin to the KLX300 than the first KLX250 back in the 90's.

Regardless, the nice thing is that you can do all the common mods to this bike and add a bigger bore later with not having to reinvent the wheel on your previous mods.

 

I have a Q4 and a MB header pipe and haven't had any problems with the setup. The MB bulge is too far forward in the installation to be too close to my legs. I commute in blue jeans and thick boots and nothing has gotten burned so far. I don't do any trails/track type riding, etc. so it may be different under those circumstances but not on the paved/dirt roads I ride on.

 

+1 for doing header and pipe and rejetting first. Do this, break it in right and be patient, these motors really seem to break in and hit stride more than others I've had, I think I hit something just over 1,000 miles and all of a sudden it just woke up and had some more. Still no corvette like my KTM LC4 640, but actually much more fun to ride outside the interstates. I do want to do a 351 eventually so I can get throttle only wheelies, but no complaints in fun factor

 

You will be waiting a Looooooonnngggg time! hahaa

I put my 351 kit on at like 1k miles and wish I did it the day I bought the bike.. It's that good.

 

Thanks for all your input.

Your probablly right that I should start out small and work my way up to the 351 since I will need and want the other parts anyways. It's just the 351 sound soooo tempting to jump into right away

 

Yea it burned a hole in my jeans. But I was just looking at it and the header pipe is much larger than the stocker so I'm pretty sure itll perform better than the stock pipe. I just have to figger out a way to put a heat shield on it.

 

Ditto the heat shield planning