No Brakes,

It feels like I have been lurking for months. I have a 2007 KLX 250S on order. It is supposed to arrive in a few weeks. I am thinking of doing the pumper carb mod first, and not bothering with rejetting the stock carb. I used to own a CRF230, and my only complaint was not being able to blip the front end up over rocks, trees, bumps, etc. From you video, the pumper carb allows you to do this. Any thoughts on this? I am new to the dirt bike scene, and the thought of changing out the carb seems easier than tackling a 300 cc upgrade or 331 cc big bore upgrade.

Any thoughts would be most helpful.

Thanks,

Mark
Calgary, Alberta, Canada

 

Well Mark, aka Maverick, welcome aboard the board.

If you can hold off just a bit, my Mikuni Pumper carb is headed out to the "specialist" to be fitted and tweaked for the KLX.

Once it arrives back here, I'll be posting an article, impressions, problems, results, etc.

Might this help you?

 

Definitely. How soon do you think it will happen? I am traveling to Arizona at the end of the month, and would like to order something so it can be delivered to my buddies house (saves on duty, shipping, etc.).

Is that just a different brand of pumper carb? Are you trying to see if one brand is better than the other?

I was a little scared off at first by No Brakes comment that his carb needs fine tuning. From what I have read, those carbs are difficult to tune. However, being able to get the front end up without clutching is very important to me, and his carb doesn't seem to be too far off tuning wise.

Thoughts?

Mark
Calgary, Alberta, Canada

 

Well, the guys over on ThumperTalk will tell you the FCR makes all the difference in the world. I'd say they are right, however, mine is still not quite jetted correctly, but even so, it is fairly close and it is a definite improvement over the CVK. I've ordered the recommended jets and needle - I'm told to expect them in 10 to 14 days. [&:]

I don't know how well it would work on the 250cc, though. I never got a chance to try that out. But I think it should be OK, but again, I wouldn't take my word for it since the only configuration I've had my FCR installed is with the 331cc bore.

I'd have no qualms about trying the FCR first, though, it should work. The 35mm might be a little large for a 250, though. One thing I'd do, though, is upgrade the exhaust at the same time or soon after to get the full benefit. I think the pipe, airbox, and carb mods need to be done in tandem. You won't realize much of an advantage with a hopped up carb if you don't get that air volume flowing in there and some more fuel to richen it up. And you won't get the full benefit of that, unless you can get the exhaust out.

 

Woops, looks like I was too slow in posting and missed Marty's response. If you plan to stay with the 250cc, then the Mikuni TM33 may be a better choice. I've heard good things about both carbs, though. The deciding factor may be what size displacement you have.

 

Thanks for the data No Brakes.

One of the things I found attractive with the one you got was that it was set up for you prior to shipping. All you had to do was pull out the old carb and put in the new one. That is attractive to me. I am not vary mechanically inclined, and with all of the money floating around this oil and gas city, to get anyone to do any work on your bike is major bucks (ie. $90/hour). I am a bit concerned about Marty having to send his to a specialist, but maybe once they get it fitted properly it could be made ready to ship like yours was.

I guess another option is for me to save my money and to the pumper carb upgrade at the same time I go to 300 cc's. Does your carb work with the 300 cc bike, or does one need to go to 331cc's?

Mark
Calgary, Alberta, Canada

 

Well the reason I chose to go with the Mikuni is largely due to cost.

The Mikuni carb, part number 13200-14D03 (Ron Ayers has them in stock), is under $300.

A gentleman I bumped into on one of the forums has done the mods before, here is an idea of what he is going to do:

The offset I mentioned was so I could bore it out to the 34 mm this lets me enlarge the bore without touching the bottom of the carb bore. You are correct about the adaptors. I used a file & micrometers to make the flanged round then made the adaptors I made them .002 smaller than the carb flanges, heated the adaptors up to 200 Deg. froze the carb so they would slip together also used high temp lock tight to make a air tight seal after it cooled & set up I finished turning them to size put the same groove as the stock CV carb so it would fit tight. Could use only one cable I used two tight fit.

Once I get the carb back, mounted and ready to rock and roll, if I am pleased with the work, I am going to ask if I can post his contact info for everyone to call and order some of his work.

The Keihin FCR runs in the $600 area.

Just trying to come up with alternatives! That's all.

 

Sounds cool. Hope it works good. When do you expect to have it?

Sounds like NO Brakes pumper carb may not work on my machine as I am only at 250 cc's.

Are you still running at the stock 250cc? I think I am going to stick with that for a while. If I can get the front end up with no clutch at 250 cc's, I will be very happy.

Mark
Calgary, Alberta, Canada

 

No Brakes,

Do you know if Keihin makes a small pumper carb that would work on my 250cc bike. Sounds like yours might supply too much fuel.
Maybe I will call the guy that fitted your carb and ask him. Do you have a name and number for him?

Mark
Calgary, Alberta, Canada

 

From what I hear it works great with 300cc though I haven't tried it myself. I think the key with being happy with the FCR is getting it jetted and dialed in correctly. I'm happy with mine performance-wise as-is, but the stutter is still there in the low RPM and low to mid throttle positions and I want to clear that up. I'm hoping the jetting recommendations I've received with fix that, but I'll have to wait on the parts to see. I ordered several other jet sizes in between in case I need to experiment.

Unfortunately, our starter motor is bare millimeters below the bottom of the FCR, so close that I don't think one of the Kouba or other brand fuel screws will fit. Otherwise, that would make it easier to fine tune.