Fm what gearing are you running? You guys have to remember that these are geared as a dual sport bike, not a dirt bike. The old klx250 had 14/50 gearing on it. And yes the pumper will help with the wheelie ability. I also liked the instant response as much on the street as I did in the dirt.

On thing to consider is carb size from a 250 to a bigbore. Some on here will disagree but I say the billblue 34 is too small for anything over 300cc. Check out planetklx and read what they have to say about carb sizes and cc's with the klx. And yes, if tuned right the FCR is a way better carb than the mikuni.

 

The motion pro does sound like a good idea. I'll look into it.

 

My mods are listed in my sig. I have a 13 in the front with the stock rear.

I may do a big bore in the future so if I do get a pumper now, I want to be able to continue using the same carb it even after I install the 351. I certainly don't want to have to buy another $400 carb in the future.

My plan was to go with the BB 34 as I like the fact that the carb is a direct plug n play for the KLX250S. You now got me interested in the FCR. Which one are you talking about, and would it be too much for a KLX250S? How much modding is necessary to shoehorn a FCR into the KLX250S?

 

Sorry I have sigs blocked so the pages load faster. The FCR was 35mm and I would say it would be too much for a 250. You would have to have the FCR setup from someone like Jerry at fourstrokeworks. He machines some inlets and outllets so it will bolt on to the 250s. The ones setup for a 300 will be different due to the air boots that are used. As far as mods to the bike, I belive you only had to move the wire harness over a little(no cutting, just move it). It is a tight fit in there but they go.

I would also say that the Mikuni TM36 pumper would also be a good carb for the 351. From what I have heard they will drop right in from out of the box and actually fit better that the FCR or the BB34. I was going to run a TM36 with 300cc but came across a deal on a FCR that I couln't pass up.

 

No$, isn't BB34 modified by Bill Blue to be basically a plug n play? I thought I read somewhere here that it was. I'm not sure but isn't the reason why a stock TM33 doesn't fit is because of the throttle housing hitting the top? I was under the impression that Bill Blue modified that on the BB TM34 to be a plug n play for the KLX250S and that it dropped right in.

 

Heres the settings that FSW supplied for the fcr35.

Jerry said he installs the carb on his personal klx250 to dial the carb in. Final jetting on the 250 was a 152main 55 pilot 2.5-2.75 turns out on the fuel screw. Final 350 jetting 162m 58 p 4th clip from the top of the needle 2.75 turns out on the screw.

 

Yes I belive that the bb34 is a drop in affair. From what I have heard from the ones that are running it the tm36 is a very good fit, and fits better than the tm33/bb34 or the fcr. They all fit in there regardless.

 

I would like to ride the bike that Jerry sets up the carbs on. Most that have gotten a carb from him have had to make jetting changes and not just one size. I belive that nobrakes had to change the needle as well, and I think mine was border line on the needle. Most are reporting that the 55 pilot is too big. I know it was for me.

Don't get me wrong Jery is a very smart guy when it comes to the klx, I would just like to see how his bike runs with this jetting, I know mine wouldn't.

 

I think the TM36 and the FCR is going to be too much carb for my 250. If BB's TM34 is plug n play, I think I'm going to go that way. I'm not sure if I'm going to go big bore. I just want to be able to loft the front over small obstacles like a log without clutching it in first gear. The BB TM34 should be able to accomplish that, yes?

No$, I did a quick seach regarding your statement about TM34 being too small for the 351 and I did see some complaints about that. However it seems like it was from people that removed the airbox lid. It seems like the 351 is pretty much at the upper limit of the TM34 and tossing the airbox lid crosses the line for the TM34, but with the lid on, it is still ok.

 

Yes the tm36 and the FCR35 will be too much carb for 250cc IMHO. I still belive that the tm34 is not enough for anything over 300cc., but this is based on no scientific info, just my opinion.

I think most run the bb34 on the bigbores, due to the bandwagon effect. Most do not want to shell out the money for the FCR and not enough were running the tm36.

Next question is, why spend the money on mods to get more power, when you will have to put the airbox lid back on(and reduce power) to keep the carb happy?