Hello All:
Considering installing a keihin FCR35 or the Mikuni TM33 on my KLX"250"
I'm in search of feed back from those who may have installed eitherwith the stock 250cc discplacement.
Most of the postsare with the 300 / 340 big bore kits installed. I'd like to here how it works on the stock motor.
Thanks for the info!
DJFields

 

I installed a Bill Blue Mikuni TM34 (going froma modded Keihin CV34) on my bike with stock displacement. HOWEVER, the intake and exhaust systems were not stock.

The biggest noticible difference was throttle response. The throttle is directly connected to the carb slideand accelerator pump provides a shot of fuel as soon as the throttle is twisted (this is to account for the momentary lean condition). The CV carb works differently and there is a lag between opening the throttle and when the slide opens.

I think that the TM34 would work just fine on a stock bike, you'll have to spend some time getting it jetted just right for your particular setup/altitude.

 

Thanks Dan
To clarify, I have completed "all" theintake mods, installed a KDX snorkle, removed the smog stuff, and also have a HMF slip-on, and rejetted accordingly.
I'mjust looking for a little more "snap" on the bottom end. I completly understand the difference's but really need to know the true effectiveness before Igo buy one.
Don

 

As I understand it, the TM33 fits better into the space we have available... FCR35 is a very tight fit I think.
Pilot screw adjustments would be easier on the TM33 - I think there's even room for the T screw that Bill Blue can supply.

 

Don,

My bike has the 331, so I can't help much with the effect the carb will have on a 250, but I can tell you that the TM33 is easier to install. There isn't a lot of difference, but some. The TM 33 is a little shorter overall. Plus, the idle mixture screw is not adjustable with the carb installed on the FCR. The float bowl rides almost on top of the starter. The TM 33 with the T-screw is adjustable with the bike running if you wish. The TM33 has a choke. The FCR 35 does not. That could be a factor in cold weather.
I'm still experimenting with the FCR on my bike now, but the Mikuni as set up by Bill Blue was almost perfect out of the box. I'm only using the larger bore carb to see if I can get anything more at higher RPM. The stock bike could suffer at low end with the larger bore because less air is sucked through the carb. You'd be on new turf with that one.

Let us know how it goes.

Bill Dragoo
Norman, Oklahoma

 

As I understand it you don't need the choke anyway just give the throttle a twist and the AP squirts raw fuel into the engine, then just hit the magic button. (I don't have either carbie ... yet)

 

You are correct, Garry. It will start under most conditions by using the accellerator pump as a primer. It will likely die a few times when cold, until it generates enough heat to atomize the fuel better, then it should settle down and run normally. I just don't know how bad it might get for the guys in the really cold climates up North. Airplanes don't have a choke at all, but they have a primer and a mixture control.
It'll probably be fine.

Bill

 

There are quite a few that are running pumpers on stock displacement, I am sure they will chiming in soon. Tremor38 is one of them. I have heard that the 300 with a properly tuned pumper will out perform a 331 with a dialed in stock carb. The same thing should apply to the 250. If you do not plan on going over 250cc I would stay with the smaller 33mm or the bluebill bored 34mm. If bigbore may be in your future then it would be a toss up between 34mm and the fcr. The tm does cost a lot less though.

 

i have a bill blue carb on my bike with the stock jug .
given the choice between a bike with the mikunipumper and one with the stock carb. i'd go with the pumper. it's expensive though and the gains are not that significant. nevertheless i'd pick the pumper.

don't expect to get a hit like you would out of a 2stroke. it won't happen. ever. the power is more subtle than that. it is there just not so blatant.

 

I'm running the TM33/34 with stock displacement andam very satisfied with the upgrade. I see it as more of an insurance policy in cases where the only way out of trouble is to get on the gas. There were a few times though that it probably got me into trouble too. Either pumper is a good choice, but went with the TM33 due to cost.

Not sure where you are at as far as all of your upgrades, but in my case I should have probably went with the gearing changes (14/48) and the suspension upgrades before buying the carb. I got the carb first but feel like I got more out of the gearing and springs than I did the pumper. Not disapointed but may not have bought it knowing what I do today.