KX250 Wide Ratio Option

[dtsviper]

I have a 2000 KX250 that I am setting up for woods. I saw a post on changing the shift drum out for a '98 model to get rid of the "notchy" shifting.

If I am splitting the case for this, I was wondering if it would be possible to change out 4th and 5th gear sets for the 2003 KX250 gears. This would give a wider ratio top end to the bike.

Also, what about the low/first-gear out of a "K" series KX250 (1994-1998) bike? This is a 32 tooth output on the 15 tooth input shaft. The 2000 KX250 has a 27 tooth output on the 15 tooth input shaft. This would put it closer to the "granny" gear 1st of a KDX (13/28).

Any comments, ideas, suggestions?

Thanks!

 

[bscottr]

Originally posted by dtsviper
I saw a post on changing the shift drum out for a '98 model to get rid of the "notchy" shifting.

For the notchy shifting you may want to check out this link: here. It cured my shifting problems.

I hope you get answers on the ratio question. I'd like nothing more than to lower my first gear ratio. If you find out information from other sources please post it.

Good Luck,
Scott

 

[Hondaxrguy]

Scott, I tried to follow the 2 links to the discussion, and pictures, at Thumpertalk, but they changed their format, and the links no longer work. Do you happen to have any pictures of yours? I'd really like to give the mod a shot. I've almost gone over the bars SEVERAL times going from first to second and hitting neutral.

Thanks,
Jeremy

 

[bscottr]

Jeremy,
I forgot about TT changing up the format over there. Below is a picture and explanation of how the guy from TT did his. He was a little more aggressive in removing material than I was. If you notice the yellow lines, that's the angle I grinded, filed and polished to. Let me know if you need additional info.

Good Luck,
Scott

 

[Hondaxrguy]

Tell me if I'm understanding the picture correctly. The picture of the shift star is UNCUT. The black lines show where he cut to. The yellow lines show where you cut to. From the factory, the sides are almost like a banana's arc. The goal is to file off just enough to make the sides straight. Is that right? Sounds simple enough to me.

Jeremy

 

[dtsviper]

Definitely good news on the shift star. Might just solve my problems in that area!

Any thoughts from anyone on the tranny gearing???????

Thanks!

 

[bscottr]

Jeremy,
You've got it! The picture is actually from a YZ400F, but the shift star is very similar to the KX. I polished all the contact areas after the modification as well, I also polished the other parts I mentioned in the other thread. BIG difference! 1st to 2nd and full power shifts are very smooth now.

DTS,
I'm hoping someone wades in with that info as well.

 

[cujet]

Is the older KDX250 similar enough to swap a couple of gears from? If so that may be the way to get a WR trans.

Chris

 

[dtsviper]

Well, I have been doing some research on the gearing. Haven't looked at the KDX250 yet. That is a good idea! I have read that the '03 KX250 has the same lower unit, but BuyKawasaki shows new case numbers. Internals look the same, but part numbers are different.

For what it is worth, the review I read on the '03 KX250 said gearing was the same as the previous bikes ('01, '00, etc.), but that 4th and 5th had been spaced farther out for a wider ratio tranny. This is where I got the initial idea to do a gear swap.

If the KDX-250 were to work, to get six gears would require a LOT of changing - drums, shift star, input shaft, output shaft, etc...

FYI: I priced 5th gear for a '03 KX250 and it runs about $65!!!! So, 4 gears to change out 4th and 5th could be an expensive option. I am not sure what the old IMS WR kits cost. Wish I could get a hold of them for some feedback. Their website is currently being destructed (reconstructed).

Thanks for all the good information! The shift star fix is on my list of things to do!

DTSViper

 

[Matt90GT]

A 91-94 KDX250 is only a 5 sp. It is based off the 88-92 motors.

Top speed with a 13/50 gearing is still 74mph for me on the KDX which is better than the 60 in my older CR250

 

[Sphinx]

Just out of curiousity what about the KLX and KLR transmissions? Anything which would swap over?