If you have the cylinder off, could you post some measurements of the skirt part that fits into the crankcase? I'm curious how it differs from a '09 250 cylinder.

 

Sure. Tell me what you want

 

OK, so a couple of observations from today:

I think Kawasaki has been lying to us. The 300 forks are rated at 11.2", and I'll be lucky to even see 11.

My shock measurements were a little different than the previous post. I hung the shocks from a 10 mm rod, threaded a 10 x 100 bolt in the bottom and measured between them.

300 shock 16.875"

09 250 shock 16.5"


The 250 linkage is different than the 300 with the distance from the frame mount to the dogbone mount being about 10mm (~3/8") . The dogbones are also 2.5 mm longer on the 09 (119.5 vs 117).

Using just the 300 shock raised the bike (lowered the rear wheel, unloaded on a stand) about .625. Using the 300 linkage (250 dogbones) added about 1" travel, with the same bike height. Swapping the 300 dogbones on would have added about another .25" or so in height, but slightly lessned the travel. Best travel was with 300 shock, 300 linkage, 250 dogbones, and it was about 10". I'm not sure how they're getting the quoted 11" as the swingarm distances measure the same.

Fork overall lengths measure about 35.25" on the 250, 35.75 on the 300. The 250's were done on the bike, so they could be a little off. There is a difference in travel, and the upper tubes are the same length.

 

2009 KLX rear springs:
white = 250S; 257mm
red = 250SF; shorter than white, can't measure as it's installed, have a note somewhere.

 

OK, so I did the 300 to 09+ suspension swap a few days ago. It was pretty straightforward, but there are a few things to know.

Forks:
The 09+ springs are a higher rate, so I would have preferred to use them, but they're also 45mm shorter (same spring as 300, shortened = higher rate).
The fork rods are accordingly 45 mm shorter, and limit the travel at the same time.
So I thought I could maybe use the 300 internals in the 250 forks. That way everything externally remains the same, no problems bolting stuff on.
Everything fits, but the underhang on the 300 forks is longer than the 250's. It works, and you get the increased travel, but the forks also end up being roughly 35-40 mm longer. I didn't want that much extra height.
I also thought I might be able to use the 250 spring in the 300 fork with a 45 mm spacer. It would work, but measuring the spring, it looked like it might coil bind before it hits 11" travel, about the max that fork allows.

The caliper mount is slightly different. Bolt pattern and height is the same, but I had to machine 9mm spacers to move it (in) closer to the rotor.
The bolt pattern for the fork guards is different, but one lines up, and I drilled one more and it bent around and tightened up fine.
I also removed the wire hanger for the brake line on the bottom of the fork. Could have drilled a mounting hole, but don't think it's necessary.

The rear was straightforward.
the 250's white spring is a lighter rate than the 300's. Same height, same diameters, and same pitch, but the wire diameter is 1 mm less.
I have yet to install the 300 linkage. The one on the parts bike had bad bearings, and I'm waiting for parts.
It doesn't change the ride height, but does give about 25-30 mm more travel, so the ratio is increased, and wil reduce the wheel rate assuming the same spring. Curious to see how it works out with the lighter 250 spring. Probably good for me as I'm 145 lbs.

Have yet to ride it, but should be able to get out by next weekend.

I'll add more as I remember it

 

Installed the linkage from the 300, but with the 250 dogbones to give a little (minimal ) drop.
Height remained the same, but I was right about the difference in ratio. It made the rear softer, and changed the sag I had set at 75 mm to 100 mm. I reset it to 85, and it feels much better. Before the adjustment it felt really soft.
You can see the difference in the linkages. 250 linkage on the left

 

Was that with the 300 shock or the 250?

 

If you read the previous post, it was the 300 shock with the white 250 spring

 

Any results from riding? Is the bike one inch taller and the suspension working better? I like the idea of what you're doing, but pirelli mt43 trials tires add one inch of height so i might just go that route.

 

So I've had a few really good rides on it now and I'm really happy with it. The bike does sit higher, but I'm not exactly sure how much. I forgot to take those measurements before I started. Ground clearance is increased, which is one of things I wanted to accomplish. If somebody wants to take some measurements on their 09+ bike, we can compare.

It handles great. I've never been as fast on this bike as I have been on my last two rides. Not even close. The rear spring rate is just barely enough for me at 145lbs. Sag is set at 85, and I might tighten up a bit to 75. It is bottoming, but only on fairly extreme sections on thee trail, and high speed. On the MX track, it doesn't take much to bottom, but that's not what I'm using it for.
12 mm preload spacer in the forks, 3W (same as 5) oil at 100 mm, forks up in the triples 15 mm, and sag at 85, it feels very balanced like it never has before. I would say if you do this swap, unless you're under 150lbs, I would use the 300 spring. Also, where I have the forks set, and considering that the travel gain is only about .5" or so, I might just stick with the stock forks.