Hello to all. I have recently been having some carb trouble and I had the thought of just replacing it all together. I would like something more responsive than the CVK34 anyways. I mainly ride the bike on the street but do take it off road somewhat often. I was thinking about getting the TM 33/34 Mikuni flat slide pumper carb from B&B Cycles since I plan on doing a big bore kit from them in the future. Has anyone used this carb on a stock bore KLX250? If so, what are your thoughts on the upgrade? I have full FMF exhaust, K&N filter w/lidless intake box, and MCM.

EDIT: Bought TM36-68 and installed. All the tuning and jetting info I posted is based on the TM36, NOT TM33

 

It will work fine on a stock bore as long as you have it jetted properly. I even had the 36mm pumper Mikuni TM36-68 on my stock bore KLX. It had a full Muzzy exhaust and modded airbox. It worked just fine. Shortly after I did a KLX300 top end, but the 250 can run either carb.

 

I've read a few comments from others here who say it is the biggest change they did in performance gain. Direct cable action and virtually instant acceleration, no hint of lag. Plus the bigger carb will flow more. I think if you do a search you may find some threads with some jetting recommendations to start with. I would say it is the best performance mod to be done on any stock set up. When we went flat tracking with our Bultacos the first thing to try to do was go up 2mm on the carb size. Nothing else did as much.

 

I know of course proper jetting is a must as with the CVK or any other carb. Direct cable actuation is a big plus as well as the pumper. Seems like the logical thing to do is get the Mikuni. TNC, was yours set up for your specific application with some minor adjustments? Or are they all jetted the same and the user needs to jet and set up the carb for their setup.

KLX678, do you remember where you found that info? I did a little searching about the TM but couldn't really find anything, but I also didn't do any real deep digging. Also hope your shoulder recovery is going smoothly, I broke my shoulder a year and a half ago and its no fun

 

The TM36-68 does not come jetted for the KLX250 as delivered. If I recall it came jetted for something more along the lines of a 4-stroke in the 350-450 displacement range. I'd give you some numbers for the application to the 250 KLX, but it's been years since installation. I still have the numbers for the 300cc application. I'm not sure on Bill Blue's jetting for his 34mm, but I think it's optimally for the 351...though he may have numbers for a stock 250 just due to dealing with various customers over time.

I originally got my jetting numbers for running it on the 250 by looking at old threads on this forum from at least a couple of knowledgeable folks who also ran the 36 on the 250. I only had to tweak a couple of small moves to get optimum performance. Another oddity about the 36 pumper is that I got better fuel economy with it than the CVK-34.

 

I found D Pippin's jetting was in his web site click here to find it. It is down a ways. Gets you in the ball park.

 

DP's settings are exactly the same as mine for the 300 cylinder, full Muzzy exhaust, modded airbox with one exception. I have 2.5 turns out on the fuel/air screw instead of his 2...a minor insignificance due to any number of small differences. I'm at about 1750 feet altitude. Amazingly I have been able to go to high altitudes without rejetting. I've gone over Imogene Pass between Telluride and Ouray at over 13K and only had the engine "burble" a little and I had to turn the idle up approaching summit...and this only lasted for a few miles. I'm still not totally sure how a non-CV carb that is a pumper gets that done.

 

It's because your bike likes you and wants to do its best for you.. Isn't that obvious?

 

LOL!...well, I gotta admit this bike has never left me down, and I really appreciate that. I've been out in super remote areas by myself, and sometimes when I stop and look around, I think, man I hope this bike keeps running. It has always started, it runs great, and it's been about the most solid, reliable dirt bike I've ever owned.

 

thanks for the link and all the great info. do you know what the difference is between the TM33/34 and TM36-68? im guessing the inlet/outlet of the carb are different sizes, but there's gotta be more differences than that. i havnt seen the 36/68 anywhere except TNC's set up. TNC, did you need to make any modifications to fit or was it just plug and play? on the B&B website it says the 33/34 has custom built adaptors on both the head side and the airbox side so it will fit the stock carb boots, its bored to 34mm, and the throttle is modified to work with stock cables