Was just wondering since you seem to be the only one that did the 300 kit and are going to the 331 overbore. What is the cost difference between the complete 300 kit and if you buy the cylinder have it bored/sleaved and get the 331 piston? Is it cost effective if you are going to buy the 300 kit to not spend the money on the 300 piston and get it bored right away and get the 331 piston? Also to clear things up when doing the 300/331 you do or don't need the 300 head, and if you don't are there any advantages to using a 300 head. Thanks

 

If you think you might go all the way to 330cc, then you are better off to skip the 300cc step and not buy the piston, rings, gaskets, etc. This will save you about $160 in those intermediate parts. You still need the 300 cylinder which is around $310. I'm using Kustom-Kraft.com for the 330cc work, and their price is $440 + you provide them your cylinder, or about $750 total. Their price includes all the cylinder work (boring, plating, honing) plus all the parts you need to complete the job (piston, rings, gaskets, piston pin and clips).

You do not need to use a 300 head. I don't know of any advantages to doing so - I think the only difference is the exhaust port thing where the EPA hoses hook up. Most folks remove those anyway and cap off the opening.

 

so it would be about $250 dollars more to go right to 331 than if you just went with the 300?

 

Yeah, I guess about that. That $250 I guess would be roughly the price of boring, plating, honing, and any difference in the other parts (piston, etc).

Obviously, I'd recommend going direct to 330cc, since that's where I'm ultimately ending up. But 300cc wasn't bad at all - it's just not quite there with what I want. It's close. Perhaps if I'd gotten the new carb by now it would make the difference and 300cc + pumper carb would be where I want to be and I'd stay at 300cc and not feel the need to go to 330cc. But the carb is so long delayed and back-ordered, I figure I'll go to 330cc. And since I can't ride due to my injury, it doesn't matter that my bike will be down for two weeks in the height of my riding season - I can't ride anyway. All that factored into my decision and the timing of it.

 

You know I could be wrong here but my understanding of Carbs like these is there not going to give you any more horsepower per say but will give a better and more instane throttle responce. Same with my Mikuni on the sporty. It doesnt really give more horsepower then the stock carb but better throttle responce. 300 or 330 I think it will run the same with the pumper carb. My 2 cents....



LV

 

Yeah, I'm aware of that. I did a good bit of research before I plunked down the money for it and have my expectations set accordingly. My understanding on the pumpers is the instant throttle response and some have described it as turning the KLX300 into a "wheelie machine". I don't know about that last characterization, but we'll see. My throttle response is actually pretty good with the CV carb, so I'm curious to see how much faster it can get. Also, I realise the FCR carb in particular can be more finicky to tune as it has more jets to adjust and more fuel / air screws to adjust. So it is highly tunable which means it can really be dialed in for great performance across the entire RPM range. On the flip side, it can be hard to get it dialed in for optimal performance. That's one of the reasons I bought it from where I did because the owner indicated that, based on his experience with this carb on the KLX300, he would select and adjust the various jets and screws to a reasonable starting point for me.

But I still want to get it and get it set up and dialed in before doing a dyno run, just so I know the final end result of at least my "Year 1" mods.

 

I bought the mikuni for the sporty for All the reasons you just listed for your pumper. Since I never jetted the stock carb I could not tell if there was any difference other then quick throttle responce. For me the thing I noticed was I dont have have burp/fart type issues that people have with their stock sporty carb. The mikuni was a lot less then what you paid for your pumper. I personally could not justify that type price for a carb. Now the 300/330 upgrade I can Somehow justify to myself.


LV

 

Nobrakes,

Sure does sound like you are fully understanding the "Pumper Carb" addition.

Back when I was running the drag car, I had installed dual 70 cc accelerator pumps and high volume "squirters" on the Holley carb on the car. The reason is that at initial throttle opening, you are squirting raw fuel into the intake to cover up the lag time of the air flow reaching the cylinder.

Right now, when you open the throttle on the Keihin CVK34 carb, there is a lag from the time you actually twist the throttle until the signal from the engine causes the slide to open and feed more air/fuel mixture to the engine. In essence, the throttle is not connected to the carb opening mechanism in this carb. The throttle being opened "allows" the slide to move up and let air flow through the carb to feed the engine. There is a certain amount of lag time. By drilling the slide, you allow a bigger "signal" to be sent that will allow the slide to respond quicker to your input.

With the FCR carb, the throttle is connected directly to the butterfly in the carb. When you open the throttle, the first thing that happens is the accelerator pump shoots a bit of raw fuel into the venturi and feeds the engine's immediate need for more fuel. It takes all the lag out of the system we get on our KLX250 when they come from Kawasaki.

Of course, there are good things and bad things that come from this. The bike is more altitude sensitive, the jetting needs to be spot on or you will notice problems. The Keihin carb covers most of these problems up.

For the kind of riding I think you want to do, the FCR is the carb of choice. I think you will find that with the 330 cc motor and that carb you will have no problem in getting your front wheel up in the air any time you want to!