Hello,

Started riding last August at the ripe old age of 28. What took me so long?

I bought a KLX250, then an XCF-W 250. I love them both. What the KLX lacks in power and lightness, it makes up for in me not being afraid to work on it.

I need some advice from you fellas. To optimize my carb so the bike runs as good as it possibly can without me having to shell out $900 bucks to Bill Blue.

I bought the thing and it had an FMF Powercore 4 pipe on it. From what I can tell, the head pipe is stock.

The carb has been modified in the following way: The washer on the needle is in the middle (3rd position). The main jet is a #132. I can tell the main jet has been changed from stock because it is not a Keihin jet. So that means the previous owner did some jetting to suit exhaust.

It ran okay I guess. Kinda wimpy. Especially compared to my buddy's big bore KLX 331 Bill Blue.

The mods I am doing to mine are as follows:
Drilling slide to 7/64ths size hole.
Removed smog stuff, capped appropriate holes.
Rerouting crank case vent with 5/8ths hose, bypassing air box.
Installing a snorkel from a KDX 220 (currently the airbox lid is on, no snorkel)
Changing out stock head pipe to KLX300 stock head pipe.

That's pretty much all I can think of for performance mods. Unless someone else can think of any I am missing???

I know most of the performance increase will be from changing the carb. My options are to do the mods, throw the carb back in as is, get new spark plugs, see if it's running lean or rich, and go from there. Or I can get a #138 main jet now and see how that works. I read somewhere Kawasaki recommends a #138 main jet to derestrict the bike (I will post the information below).

Any experts can give me advice on jetting/mods? All the above mods, UNI foam air filter (red one), 300 meters (1000') above sea level. I just want the thing to perform at peak with the least amount of $ spent.

Thanks guys, and awesome forum!!






Here is the post about the Kawasaki recommended derestricting methods, can't remember source but from some forum:

For Reference: Derestriction Procedure For Standard KLX250T9F
To improve the performance of the KLX250T9F model for competition purposes, the following modifications may be performed

1) Remove the carburettor.
2) Remove the carburetor slide and Jet needle.
3) Fill the 2 holes that are beside each other towards the top of the slide with a suitable plastic or metal epoxy. Sand off any excess taking care not to remove excessive material from the slide surface. (The hole in the lower part of the slide must not be filled or blocked.)
4) Alternatively replacement slide part number 43028 – 1081 may be used, this part does not have the restriction holes and is available through the Kawasaki spare parts department.
5) Place a spacer (Part # 92022 – 1003) under the needle jet to richen it up 0.5 clip position.
6) Suggested main jet for modification of a standard bike #138 (Part # 92063-1015)
7) Suggested air mixture screw setting is 2 ¼ - 2 ½ turns out from lightly seated.
8) Remove the intake snorkel from the top of the air box. (Do not remove the air box lid)
9) Re-assemble the motorcycle and test, sometimes alteration to the carburetor mixture settings may be required to obtain maximum performance. Each motorcycle should be jetted individually, however the above settings will generally be very close to optimum.

 

All you gotta do is get a DynoJet 2152 kit, order a DJ140 main jet from DynoJet ($2.00).

Install as per instructions for stage 2 except put the clip on the needles' 2nd notch down from the top (2N), use the stock slide spring instead of the DJ slide spring, and use the DJ140 main. Pull the airbox lid off and enjoy about 22hp and about 16 lb ft of Torque - so hang on!

P.S. Do not drill your slide, Do not put on a KLX300 header, The rest of your mods are OK to do...

 

This is "Best Max" performance fueling with your slipon at your altitude - you'll not loose any fuel economy, one member reports better fuel economy when driven "normally"...

 

If you've already drilled your slide, you'll have to use the DJ 2206 kit with a DJ140 main.

 

Hey thanks for the reply to my thread!

No, I haven't drilled the slide yet. May I ask why drilling the slide and the klx300 header won't improve performance?

Also, what else comes in the Dj 2152 kit aside from the 140 main jet?

Thanks, just curious to how these things work!

 

Sorry, coloring with my 2.5 yr old grand daughter... So rite quick - 300 header is no different at all, so no performance impact. Drilling the slide is a permanent mod on an expensive part that is totally uncalled for unless done along with with the DJ2206 kit - which complements the larger lift hole with a proper fueling needle.. DJ2152/2206 does not come with a DJ140 main - you call DJ and get one of those. The contents of the 2152 kit can be seen online.. All you'll use is the needle, clip, needle washers, and slide spring..

EDIT 12/2016: If running with a lidless airbox (Which is the max performance setup with slipon or full exhaust system) use the stock slide spring and a "undrilled" slide lift hole.

 

No worries! Ok thanks, that makes life easier. Cheaper too.

Any other free/cheap mods I am overlooking? What is your opinion of taking out the backfire screen in the air box?

 

Except for the MCM (Marcelino Cam Mod), No other engine mods are effective. Don't remove the backfire screen, don't port match stock header to exhaust port. Don't drill anything anywhere on the engine or carb.. If you have to drill something, drill the crankcase vent port on the airbox.

The MCM will be additional power you can taste and smell, off idle up to about 9.4K RPM with your PC4. It is not difficult to do but it there is no room for error - foul it up and you risk your engine.

 

That video of you getting the klx up without having to pop the clutch.. What are the specs on that bike? Stock 250cc engine with the dyno jet mod and the MCM mod only? And a slip on pipe I assume... Stock header? Looks pretty badass, I couldn't dream of doing that on mine as it is now..

 

That was very early in my tuning. DGR slipon, stock header, MCM, lidless, and the DJ 2152 kit installed as per stage 2 instruction using the included DJ132 main jet..AND THAT IS ALL. No other mods/performance parts at all. Way too lean but the TRQ curve was already showing its' potential..