Just curious as to what are the biggest differences between these 2 machines other then displacement? After Nobrakes does his 300 kit mod, do you think that our machines will perform just as good as the KLX 300?
I am just curious as to what the biggest things are done to the MX machines also to make them run so much stronger then our KLX 250 dual sport? What would be the biggest difference between the KX 250F and our machine? I know that the KX will be able to rip our machine apart, but what makes it so considering they have both the same displacement. I know ours has all the added weight to make it a dual sport, but what else engine wise?? I know the suspension is diff. and all, but Im just talking about the engine and the output of power and how it does this better, differenet then our bike?

 

Good questions, I have always wanted to know what makes the KX so much faster. A friend of mine had two boys that race, one has the Kawasaki 125 two stroke, and the 250F 4 stroke, and they are like rockets.

 

A couple of notable differences are the carburetor, cams and timing, as well as other factors such as compression, air intake, valves and seats, etc, etc. But just replacing one or two of these components with their racing brethren's counterparts is not going to turn the KLX into a KXF either - it's a total system thing.

Most of these racing bikes use a "pumper" carb which forces the fuel into the mixture while our CV carbs rely on vacuum to raise the needle and fuels gets delivered that way. That's where a lot of that instant throttle response comes from. Racing cams are finely timed to optimize power, perhaps at the trade-off of longevity of the valves. Racing bikes typically need a lot of engine maintenance with frequent rebuilding.

But just about everything is optimized for performance on these bikes from the air intake pathways to the shape of the piston crown.

All of these factors add up to that rocket-like punch. It amazes me to see the MX and SX pro riders pull out of a turn where they had to slow down to a near stop and then lay on the throttle and rocket off the jump right in front of them and do a double with little or no room to pick up any speed beforehand. Those bikes are amazing. Of course, they have dedicated mechanics to tune them to perfection. The factory riders, do, at least.

I think that the 300cc upgrade kit will make the 250S perform similarly to the KLX300. The bikes share a large number of components in these areas including the same carburetor and many others. And with the jetting recommendations that we've performed that are all based from the KLX300 community as well as a KLX300 aftermarket pipe, I think they will be very similar indeed! But a racing bike it is definitely not. The KLX300 is sold as an "off-road" bike, but off-road does not equal MX.

If you want that racing bike performance, it would not really be cost-effective to try and transform a KLX (300 or 250). That's not to say you can't race one of these. Sdunne proved that you could and could do OK, but even he eventually went with a YZ250F if I recall. But I would argue that for general off-road and trail use, I'm not sure racing performance is all that desirable. But that is subjective and each person is going to have their own definition for what they like the best.

I have no illusions about what the 300cc kit is going to do. I want more low-end grunt. I want to be able to lift the front end more easily for clearing logs and stream crossings on the trail. I don't race, so I don't really need high RPM performance. I might end up replacing the stock carb with a pumper like the Mikuni TM33, but I'll assess whether that is something I want to do after I get a feel for the bike after the 300cc upgrade. I don't want to make too many changes at once and would prefer to get a good feeling for what each upgrade has done for me before doing the next one. The Mikuni pumper is actually a farily cost effective upgrade at about 1/2 the cost of the 300cc upgrade. But the pumper is not going to give that low-end grunt like increasing the displacement will and that's what I'm really after so the 300 kit makes more sense for me at this time. But even with the pumper, it's NOT going to have that rocket punch of a racing bike. But that's not really what I want, though, and I'm not trying to turn my KLX into that.

 

Thanks for the response, I also do not want to turn my bike into a MX bike, but I was just curious as to what makes a mx bike so powerful.

 

Nice accurate thoughtful answer Brian

cheers

 

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What did all the bits and pieces cost to upgrade it to the 300? Is it much louder?

I've been contemplating a dual-purpose bike and wonder why one would buy the KLX250S, then modify it? Why not buy a KTM or Huskey; which seem to be more off-road capable to begin with?

What are the advantages going with the KLX' as so many novice (like me) off-road riders and experienced one's, as well, go with it?

Thanks ~ Walt

 

Green is my favorite color? (Woman's answer)

 

Ok, do you know the total cost for the upgrade?

Thanks,
Walt

 

Hi Walt,
A novice rider could get used to the power and handling of a KTM / Husky / Gas Gas but quite easily get into trouble with it as well, the KLX is a lot "softer" and makes a very good bike to learn / relearn on. The KLX is also a much better road bike than the above and so is a better dual sport. If you want a good dual sport to learn on the KLX is ideal, if you want a potent enduro bike which is road capable than the others are better. The KLX is also cheaper than the others and can be upgraded and still have change left over from the purchase price of the exotics.
Cheers
Garry