XR400R or XR600R or ?

[HomeMadeSin]

Here's the deal: living in dirtbike paradise, AKA Colorado. Want a strong, dependable bike for riding trails throughout the mountains. I've had a '83 XR200R and '84 CR250R and liked them both. I'm struggling with everything, from 2 smoke to 4 slow, etc. The XR was fuel and go, no problems, but with the CR, I had to drain the carb, clean the plug after every ride, even running leaner than factory. XR handled like a YUGO, and the CR was a dream to ride. :) So, I'm thinking massive 4 stroke to get the power and dependability. But what about handling? Have the XR's improved? Should I go 400 or bigger or what?:think

I'm a little concerned about jetting/elevation issues. Can't believe C'dale was the only one with balls enough to put FI in dirtbikes....:mad:

 

[MR. CRF]

THE CRF450R IS LIGHT, VERY POWERFUL AND EASY TO RIDE . THE XR650R IS NOT LIGHT, BUT VERY POWERFUL AND VERY FAST IN THE OPEN SPACES. AN XR400R IS OK, BUT IT WILL LEAVE YOU WANTING MORE POWER. A WR426 IS NOT A BAD CHOICE EITHER AS WELL AS A KTM520EXC. AND THE KTM HAS ELECTRIC START!

 

[wayneo426]

CRF- QUIT YELLING!!! :)

I would imagine you need something "flickable" for CO. IMO, the 600 is too much of a beast for tight singletrack, the 400 is nicer, maybe underpowered, the KTM's are great, (520 rocks!), but pricey, which leaves the WR. I guess you already know the answer then!
426 BABY! YEEEE-HAAA!!!! :p :p :p

 

[TONYKX]

In 92-93 I took Cr 250 to Colorado,good power have to jet it right but will lost power about 50 % on high elev.
In 94 I took xr 600,it good up hill,no jetting change because of big size motor.
But down hill is scarry,rear wheel try to pass front wheel (weight).
In 96 I took xr 400 up there,re jet with couple side leaner everthing just fine.,up hill or down hill power good every where fail many time,include in the water crossing friend of mine rode KLX 300 broke his radiator.
Now I have kx 250,xr 650 and wr 400 .,my oppinon,for remote area I belive in air cool 400 is the best.,for in town I love the blue .I will not recomend for
either xr 600 or 650 unlees you are 250 lbs.plus that would be another factor.BUT for KTM magic button is really help you going with confident if you are a little guy.
TONY

 

[scar tissue]

I've owned the XR600, great motor but heavy, ridden the XR400 several times. Lighter but less power. If you were choosing just between those two I would chosse the 400 for single track, and if you want more power simply build it to 440, and/or go with a pumper carb.

Honestly, I was donig the exact same thing you are, I wanted power, easy to maintain, but not big and bulky. I settled on a KLX, built by stroker to a 340 with a pumper carb and all, est.HP by them is 42HP. but it only wieghs 230lbs. Best of al they handle great, much better than the other two, and cost a lot less. especially if you go used. You can find 2000's for $3K have stroker do the work and have a sweet ride for less than you can buy the others used in stock condition. Good luck.

 

[HomeMadeSin]

Pumper Carb?

Thanks for the info. BTW, what is a pumper carb? Maybe I've been out of it for a while, but I have never heard of it.

 

[scar tissue]

Re: Pumper Carb?

Originally posted by HomeMadeSin
Thanks for the info. BTW, what is a pumper carb? Maybe I've been out of it for a while, but I have never heard of it.

Here's the info from stroker. From personal experience, these carbs really make a difference on XR's and KLX's.

What is the difference between a "cv" constant velocity type carburetor and a "pumper" carb? What about other after market companies selling "flat slide" two stroke carbs? They are cheaper, but how do they work?
Most fourstrokes come with a constant velocity carb on them. The way they work is when you twist the throttle, the slide doesn't go up. Instead a butterfly opens and allows for fuel to enter the motor. Once the motor builds up pressure, the pressure raises the slide. This is why the "CV" type carbs have no bottom end throttle response. There are other after market companies that sell "flat slide", two stroke carbs as a replacement to the "CV" type. The problem with the "two stroke" carb is that it doesn't have the fuel circuits needed for a fourstroke. The result is that you will have better mid and top, but the bottom throttle response will be worse than the "CV" type. At Stroker, we have put "accelerator pump" carbs on fourstrokes since we have been in business. People thought we were crazy. What these people didn't know, was that they have been in use on fourstrokes before we did it. Just no one put them on off road bikes, except us, until the new YZF400 came out. Now that the YZF400 pumper carb works so well for that bike, and comes from the factory like that, those people that thought we were crazy, are now using pumper carbs. The reason the manufacturers use the "CV" type carb, is because it is user friendly and is not as sensitive to elevation changes as the "pumper" carbs, and it's cheaper to make them. Sometimes cost is an issue when manufacturing a motorcycle. For performance, there is not a carb out there that will beat a "pumper" carb. We have seen more and more "new" fourstrokes coming out with pumper carbs on them. A pumper carb works like this. When you twist the throttle, the slide raises up, and an injector squirts raw fuel in the head. (Just like a fuel injector )This is where you get your instant throttle response with this carb.

It says here pumper carbs are more sensitive to elevation changes, I've ridden from Kennedy Meadows @6-7,000 feet and Big Bear at 4-5,000 to where I usually ride at 1,500 - 3,000 ft. I have the jetting set up for roughly 3-5,000 feet and it's worked pretty well at those other elevations.