I'm looking at both of these pumper carbs. Initially they will go on a stock engine but, I'm going to do a big bore kit sometime this summer.

I've done some reading online but, I'm not sure what I'm getting into with installation and jetting. Do I need to do airbox and boot mods for either or both of them? How about throttle cables and frame modifications?

I'm hoping a carb change will help my cold starting problems (winter time <50F) in addition to adding some throttle response. A carb change won't add any power will it, just better throttle response?

Thanks!

 

I have no direct experience with the FCR 35. Everyone who installs one swears by it, but that's all I know.

That being said, I can tell you why I went with a TM36. First off, price. An FCR from Four Stroke Works runs $600 +, a TM36 can be had for less than $300.00 if you shop around. Second is fitment. The FCR needs to have adapters front and rear to fit the KLX (hence it's hefty price), while the TM36 is a drop-in. Finally, familiarity and simplicity. I already had a bunch of Mikuni jets and had jetted many of them. There are less jets to changed on the TM36 compared to the FCR, which makes it simpler to jet. The accelerator pump comes with adjustable starting and stopping points, eliminating the need for the "taffy mod". On the other hand, the full range of adjustment the FCR offers might be what makes it better (albeit harder to jet). Again, I don't know.

With a TM36, you ditch the "push" cable and only run the "pull" cable. There are no frame modifications needed. You may need to slide the boot on the airbox side of the carb forward about an 1/8 inch because the TM36 is about 1/4 inch shorter front-to-rear than the stock CVK carb. This is actually a blessing because it is much easier to get the carb in and out. You will probably want to take the lid off the airbox, even with a stock motor. Some guys run the TM36 with stock jetting and a stock motor and are happy. I've only run mine on a 340, so I don't know how it runs on a stock motor. With the some mods (exhaust, big-bore kit, etc.), the carb will add some power in that it will allow the engine to breath better. In any case, a pumper carb will vastly improve throttle response.

 

Wow Mustang,,, it wasnt even my question but Now I would rather have the TM36,, thanks

 

Do either of these carbs have a spot for the factory Throttle Position Sensor? or do they have their own....

 

I went with the Mikuni "34" from Bill Blue.
Bill had done all the hard work so it was easy.
Sometimes I think, should I have punted on FCR?
I here it's better but I don't know for sure.
BTW, I also have the 300 kit.

 

None of the pumper carbs use the throttle position sensor. I just unbolted mine from the stock CVK carb, wrapped it in electrical tape and tucked it up into the wiring harness. It seems to have no effect on performance.

 

I was going to go with the tm36, but got a good deal on the FCR. I am not sure if the FCR is worth the extra money. The money you save by going with the TM36 you almost have the big bore kit.

I also think that either is overkill on 250cc. Just my own opinion. I did notice a torque drop from the cvk to the fcr. That 1mm increase must have done something.

 

thx neilaction! i always wondered bout that!

 

I have the exact opposite experience with the fcr35 on the 250. Low to mid range was the most improved imo. Top speed is the same... plus no lag in throttle response.

 

If you can get a new Mikuni or a gently used Keihin for the same money, which would you get and why?

I' leaning towards a Mikuni because they seem to be easier to install and easier to adjust but, I haven't spent my money yet ....