MX to Sumo Conversion

[shilka99]

Heres my latest project, converting my KTM dirtbike to a super motard. This will allow me to use 17" rubber and perhaps even ride it on the track, specifically the 1.3 at Cresson.



I'm starting with the rear wheel only as rubber without knobs for the stock 19" wheel is non-existant and afterall, hacking my mx tire with a sawzall is kinda ghetto... With this rim laced onto my existing hub I'm going to fit this tyre:



Past experience has shown rains to work well on dirt which is all this tyre will ever see. Once I get the front converted also I'll go to a harder compound to use on the track, maybe slicks. If I need more grip in dirt once I'm using it on the track as well I can cut some tread in them with the tire groover I've had for 20 years and never used...

I should be able to get this started on Monday. I'll post updates provided it isnt too embarassing.

[shilka99]

I finally got a chance to start working on this. I ordered the rear tyre today then came home and started with this:



Lucky I have my trusty Harbor freight tyre changer and NoMar bar.
I tried removing the spokes the tidy way but they were rusted solid. Easy solution:


A little no-seize lube on the new ones:


Paying careful attention to sprocket offset:


Five minutes later:


Five minutes after that:


It really was that quick.
Probably less than an hour after pulling the wheel out of the KTM I have this:


I'm told this was the easy part. Truing the rim will apparently take a lot more time. No problem.
Apparently the tyre is in a Texas warehouse so will be here soon. Should be able to go riding this weekend.
Cant wait to try that rain tyre on grass.

[shilka99]

I spent (my boy's) naptime truing the wheel. It really wasn't hard. The most difficult part was coming to terms with this cheap rim and its questionable build quality. Where the rim is welded together there's a .020" high ridge. I was able to get the rest of the wheel to .005" runout before being hit by the bulge.
All I need now is that tyre.

[milesmiles]

This is going to be awesome!

[shilka99]

The tyre arrived today:


Lucky I went for the 4.25" rim instead of the 4.5" or 5" - its a really tight fit.




Its 5 weeks before my next track day at ECR, so I should be able to take this thing to Haslet at least once before then.

[milesmiles]

that looks awesome, do you have enough clearance between the chain and tire?

[DarcShadow]

Man, that's close. I forsee some odd wear developing on the edges of your tire (the correct way to spell it )

[shilka99]

a little chain rub never hurt anyone. I've seen some factory motards (my old VOR) with even less clearance than this so I'm not worried. When I get a longer chain/smaller chainwheel I'll be able to move the wheel further back and that will create more clearance on the right.

[Firewa11]

One thing in your conversion project I would get if I were you is a chain guard. Since the swingarm on most off-road bikes are much smaller, and the distances between the chain and swingarm are larger, it's a bit easier to get a limb pulled into that space if you're tumbling and get something pulled into the chain and sprocket, something you don't want in there (like a finger, arm, foot, etc...). Other than that, looking good!