The stock throttle has two cables - when you twist the throttle grip, one cable pulls the throttle actuator on the carb and the other pushes by the same amount. The pushing is not its real purpose though, it's there so that if your throttle cable sticks you can forcibly twist the throttle back to the zero spot and in that motion, the "push" cable operates like the pull cable and pulls the throttle mechanism closed even if the return spring isn't strong enough to do it on its own.

If you have only one cable, you twist the throttle and it actuates the carb's throttle mechanism and when you let go, the carb's spring is the only thing available to close the throttle. So if your cable sticks open or something, and the carb spring is not strong enough to pull it back ... well, you go racing off in whatever your last direction was [&:]

So the push/pull cable setup is a bit safer, I think. But there's nothing inherently unsafe about a single cable setup as long as you keep the cables cleaned and well maintained.

The price for the 300cc as I purchased it from RonAyers.com was $470 if I recall. I installed it myself so I didn't have to pay anyone for that but I think you'd probably figure around 3 or maybe 4 hours labor for a dealer mechanic to do it if you don't want to do it yourself. The 331cc kit was $440 but you have to supply the cylinder so it is really $750 which is cheaper than first doing the 300cc and later deciding to go to 331cc. If you can spare the extra $250, I'd recommend going straight to 331cc.

The carb was $600 from FourStrokeWorks.com all set up and ready to go. It took a long to to get to me, but it was worth the wait.

I just got back from a short but wet ride - I can't stop smiling, and I can't wait for some good weather. The ground is soaked right now and every time I twist the throttle, my rear wheel breaks free and sends clods flying everywhere. If you are real gentle on the throttle, it is controllable, but if you whack it open there ain't nothing stopping it, something's gotta give - either the rear wheel will break free or the front will come up. It's going to take me a little while to get use to this.

 

I wonder how a pumper carb would work with just a big gun exhaust and new air cleaner but stock cyl maybe a 33mm or something.

 

Niiiiiiiiice! Now there's even more things to think about this winter.....what to do, what to do!

 

I don't see any problem. As long as you are jetted properly, It should work just fine. Sullydirt runs a TM33 on his KLX250...maybe you can PM him. He also has machining capability and can make some adapter rings and give it an off-set overbore to 34mm for a very reasonable price. I believe he hard pulled his TM33 from a DR350.

 

Hey I didn't know Sullydirt installed a TM33 ... how'd I miss that bit of news? You're holdin' out on us Sully!

I'm still learning this carb stuff but I would think the Mikuni or the FCR would work well on the 250, assuming it is sized to match. The cool thing about these carbs are two-fold - first you have the little squirt of fuel from the accelerator pump to get things moving fast when you open the throttle and the second is that the throttle cable is connected directly to the slide. This is in contrast to our stock CV where all the throttle cable does is open the butterfly valve and it's up to the engine vacuum to raise the slide. We all did the "drill the slide" mod to improve throttle response and that was great, but it doesn't get any better than a direct connection to the throttle cable. Except for may fuel injection but that is not really an option for us.

 

hey i found a pic of you trying out your new carb....

 

That's what I looked like 3 weeks ago, only difference was I didn't have my knees under me ..... I was flat on my back!!!! My son almost crashed, he was laughing so hard. Then he came over to me and quietly said "Dad, sometimes you really embarass me!"
Anyway, I had to replace the rear fender and straighten my license plate.
But hey, it was kind of fun.

 

Oh man I hope not! You can bet I'll be riding with full concentration while I figure this thing out. It's like a whole new bike - lots more than I'm used to. I realize it's still probably not in the same league as the 4-stroke MX bikes like the YZ250F, but if that's what any of us wanted we wouldn't have purchased the KLX to begin with. However, these mods should really transform our mild mannered KLX into an ultra-fun and very capable trail bike that wouldn't be left too far behind the MX guys, with the added and very important benefit for me of being street legal out of the box From some other reports I've read, this level of mods puts it on par with the off-road offerings such as the WR250F and similar - this report coming from Bill_P over on ThumperTalk who owns both his KLX300 + FCR as well as a WR250F, so I think we can trust that characterization.

 

Sounds like you're hitting the bull'e eye for our KLX nirvana! With just a bit more dialing in, you'll be splitting arrows!



So of all the mods that have done to get where you are now, how would you rate each in terms of their contribution to your current overall performance (or in other words, compared to each other, which mods have the most significant impact):

Intake Mods
Breather Mods
Smog Mods
Exhaust System
250cc --> 300cc
300cc --> 331cc
Pumper Carb
Gearing
-------------------------
Brian's KLX 100%

(Don't worry about being mathematically correct , specially since the 300cc/331cc mods are sort of "either/or", but since we know the Eric doesn't like the math stuff [:'(], we won't be grading this.)

Mike

 

Whats your thoughts on the pumper carb mod?

Is it just feeding the big 331 enough fuel to make it run as best it can, where the CVK is starving it a little bit?

Do you think a Pumper carb would give the 300 kit a boost to near 331/CVK carb performance?