So I have 2009 KLX250S engine mods so far are FMF Q4, 300cc BB, MCM, lidless with K150 and #40 pilot jets as prescribed by KLXsters helpful info and bike is different animal from stock but I’m still looking for more 🙄
Particularly with regards to the lack of throttle response. Is that down mainly to the CVK carb? Would the TM33 carb really make much difference? Or can the CVK be just as good? Need more low end for lofting the front end up more easily to get over obstacles.

Any help appreciated.
Thanks

 

You should have more lofting ability than my KLX300R - which will loft , while in 1st, with just a throttle jab and in 2nd gear by adding a little weight shift.

So lets make sure you have all the "grunt" you should..

Please specify the following:
Which header - stock or FMF ?
Q4 - stock or have you restricted it by using a "DB killer" insert ?
exact main jet - (K150 is not a choice for lidless running)
needle choice,
clip position,
Stock or drilled slide lift port ?
Slide spring - stock or DJ ?
fuel screw setting,
idle speed,

 

For best throttle response, the switch to the TM36-68 is the most common route. The pumper carb's accelerator pump is what gives that quicker response. Some go the route of the 34mm pumper carb from Bill Blue, but there's no reason not to go with the 36. Fuel mileage is still great, and the 300-351 BB's can utilize that extra 2mm bore. The jetting for theTM36-68 is fairly well hammered out for your setup. I've been running the 36 pumper for years on my '06 with the factory KLX300 jug, Muzzy exhaust, open airbox. While the KLX will never be a fire breathing beast, the pumper carb will probably provide that little bit of extra snap you're looking for.

Klxster has probably milked as much out of the CVK carb as anyone, but I hated the CVK on mine. The CVK40's on my four KLR600/650's worked quite well and were easy to dial in for a wide variety of conditions, but I found the CVK34 to be too finicky all the way from starting to running at different altitudes...and the lack of quicker throttle response you're seeking. But then I think most riders who've come from more competition oriented dirt bikes will find this to be the case with the throttle response of the CVK34.

 

Don't forget you actually control the slide with your right wrist. No vacuum action slowing or altering response. Crank the grip the slide snaps up or down... now!

 

Stock Header,
Q4 with spark arrester because of where I ride requires it,
Size 150 Main Jet N424-27, I thought that was DJ138 equivalent?
Stock needle with washer,
Stock slide port
Stock spring
2 turns out
1200-1300 idle.

Thanks

 

Thanks for your input! I was worried the tm36 would be to much carb. I read it’s fits the bike out of the box unlike the tm33 which requires adapting.

 

Klxster, is the k150 jet too small for lidless? And/or is the standard needle the problem?

 

Yes it is !
1. Your bike requires a K160 / DJ146 main jet.
2. The standard needle IS a problem on your bike. A properly shimmed stock needle is only acceptable on a certain combo ( 250cc + Full exhaust system + lidless + non-MCM)

Your bike is set up for max TRQ in the lower RPM range. It should be crazy powerful up to about 8500 rpm with 1st, and 2nd gear power only wheelies and 3rd gear power wheelies with a weight transfer. That is exactly what my KLX300R did when it had the stock header + uncorked stock silencer + lidless DJ146 setup BUT WITHOUT THE BENEFIT OF THE MCM (THAT YOU HAVE) !

Your problem is that your fueling curve is not supporting your combo of performance mods. Between the shimmed stock needle, and the stock slide spring, not enough fueling is "hitting" soon enough for best accels after the initial throttle response - to a throttle snap.

My recommendations:

A K160 or DJ 146 is mandatory and must be done first. Then:

Get a DJ 2152 kit. Install the needle with the clip on the top-most notch (making the needle as long as possible - DO NOT use any other clip setting.). Initially, use the stock spring, ride the bike for a day in the manner you normally ride. Then you may test again using the DJ spring from the kit. You will prefer one spring over the other.

If you are determined to keep the stock needle, shim it .060 - .065 shorter than stock. You can achieve this with 3 DJ needle washers. With the new main jet, there should be an improvement in lower RPM accels.

 

Thank you! So only way to get needle is to order the whole kit? I’ll order main jet now.

She definitely doesn’t power wheelie right now. Slipping the clutch she will with a good measure of throttle.

 

Yep, you gotta order the kit..
If you are ordering a DJ146, you should add to your order three DJ needle washers.