Have decided to use an FCR35 pumper carb to go along with the 292cc kit.I have a carb on order from Four Stroke Works.Question for you guys who have used the Four Stroke Works carbis does the stock KLX 250S intake manifold and airbox boot fit the carb, or do I need to get a different intake manifold and airbox boot? Thanks.

jb7

 

Hey, JB7

Yes, the stock intake manifold and air filter boot will fit. The carb's a tight squeeze into the space though. I'm sure you made it clear that you have an electric start, KLX 250, rather than a KLX 300, right? The carb inlet and outlets are different. The KLX 250 setup uses a longer carb outlet which moves the carb back about 3/4". Without that, it will not fit...no way. Did Jerry fabricate a cable mount for you? If not, you will need to do that as well. I had to modify mine a little by welding on a piece and drilling a couple of holes. No big deal since I have the stuff to do it, but it could be a slight pain otherwise. He will probably fix you up though if he knows which bike you have.

Have you, or are you planning to increase displacement? Keep us posted.

Bill Dragoo
Norman, Oklahoma

 

Shadetree,
Yes, I emailed him that I have an '07 KLX250S with the 292cc barrel and piston, muzzy, k&n, etc. I'm going to wait till I get the carb and put it together all at one time. Only have about 180 miles on the bike with the 250 cylinder on itand I have just gotten the CV carb running good. I'll see how it runs with the bigger bore and if I feel I need a little more I'll go bigger over the winter when I can't ride it. I see a lot of posts about 331's and I think 340 overbores. What exactly are the choices and who does the work. I remember someone mentioning that their cylinder exterior had been bead blasted when they sent it off to be resizedand they were trying to find paint to match the rest of the engine. Also will still be running the stock gearing with the 292, as I do mostly street riding with the bike. I'll wait and see how it goes before dropping to a 13 tooth countershaft sprocket. Sure would like to be able to do a wheelie just by cracking the throttle.

jb7

 

JB7, there are 2 companies offering big-bore kits, possibly 3. Kustom Kraft offers a 331cc kit where they take your jug, bore it, then re-plate it with Nikasil. You'll get back your cylinder, a new piston, wrist pin, rings, and all of the necessary gaskets. Thumper Racing offers a 340cc kit, which is what I have. You again send them your jug, but they will bore it out and sleeve it (and not re-coat it with Nikasil). They also provide everything you need. If you go to the Thumper Racing website, they don't list the 340 kit, but it is in their print catalog. Just call them and they will set you up. I had heard that Bill Blue was working on a big-bore kit that uses the stock cylinder instead of the 292cc cylinder. I don't know how far he's gotten with that though. Anybody else know?

Both companies will bead-blast the cylinder. Bill Blue told me what paint to use to match the rest of the engine, and it is Dupli Color High Performance Wheel Coating #WP101 Silver. It's nearly a perfect match.

I went right from stock to a 340 kit with a pumper carb, and in my case, wheelies are not a problem (no clutch required).

 

Along with the other companies mentioned, Jerry at Four Stroke Works also does a 331 big bore. The FCR35 I got from him for my 300 was set up ready to bolt on with no modifications necessary. Often he is hard to get a hold of but he is good about making sure you get what you need.

 

Now Mike, you know that a KLX won't do wheelies, even with a big bore. There you go making everybody think they will. Aren't you ashamed? <grin>

jb7, I agree with each of the guys who've answered your question. You will have to make your own choice as to whom you go with for the bore job and sleeve vs. Nikosil, but honestly, I haven't heard of anyone who has had trouble with either method recently. I used Marvin at Kustom Kraft and the Nikosil, but everything Bill Blue has done for me has been perfect too, as has the parts supplied by Jerry Leighton at FSW. Pick your poison. They're all danged good. I'm with you on the stock gearing, but again, that's a personal choice. I like to run down the highway or backroads at speed and the 14/42 does that well enough. I also slog along at trials speeds in rocks, roots and streams, but a little clutch finesse takes care of that nicely. With the big bore, bottom end isn't a problem even with stock gears. Someone mentioned or asked about vibration with the 331. I haven't noticed any at all with my build. Marvin uses a J&E piston. Let us know how it works with the 300 and FCR 35. Sounds like a good combination.

Bill Dragoo
Norman, Oklahoma

 

You're right Shadetree, I'm sorry.[sm=bustedsign.gif] A big-bore KLX is a powerless pig -couldn't do a wheelie even if the front wheel washung froma crane. It's so bad, it makes walking seem appealing. Don't waste your money. Go buya450 MX-bike-of-the-momentand be done with it. Blah, blah, blah!

There, did I set the record straight?

 

You guys aren't harassing a former KLX owner by any chance are you?

jb7

 

Thank you for coming to confession, Mike. Don't you feel better now? You have a whole week to mess up again.

What's that you say, jb7? Us? Nawww. We'd never...