94 KTM 300exc fork swap

Well I found a crack in my lower fork ear yesterday while preping my bike the the Sumter Enduro in two weeks. I talked to my welder at work and he said welding it up would weaken the surrounding area of cast aluminum and may make it to brittle to be used under the high stress of taking all those hard hits.

So my solution is to just throw the front end from my Vertemati on it with the 48mm works WP forks and billet triple clamps. I'm just going to swap the steering stems and bolt the new stuff back up. Not that big of a deal all I have to do is turn up a few shims.

Here is where I am at now.




Mock up




Stock on right. Vertemati on left



Vertemati steering shaft hole


KTM hole


Sorry some of the photos are blurry. I'll upload more as the project progresses.


Looks like a lot of incompatibility. I'd try and find some good used fork stanchions or a whole set of old forks. Maybe try Slavens Racing. I wouldn't think of welding.

Other than that I guess you could machine steel reduction bushings for the newer triple clamps and press in the older smaller steer tube. Not sure what to do on the top one to accept the smaller bearing. I guess another reduction sleeve to accept the bearing race.

Edited by modifier

Well I got the lower bushing into the Vertemati triple clamp with a nice tight fit, +0.0015" heat shrink. On cool down the I.D. of the bushing shrank a touch too much so I'll have to run a small boring head though to bring it back to size. Tomorrow after work I'll get the steer shaft in the lower clamp and start on the bushing for the top. :ride:



Should have everything done and back on the bike by Wednesday.

The Ny-locks holding the limit stops got a little hot! :unsure:

I got the KTM steering shaft into the Vertemati triple clamp and made the bushing for the top clamp as well. I'll hopefully get them on the bike tonight and maybe the forks bolted up.





Turning down the stock for the top bushing




The lower clamp is a +0.0015" heat shrink fit for the bushing and a +0.0008" press fit for the shaft. The top is a -0.0040" slip fit into the top clamp and a -0.0020" slip fit for the shaft.

Got everything all back together!!! All that is left is putting the bark busters back on for the race.

Here it is:








Old vs New.


Sorry about some of the photos being blurry. My camera doesn't do well in florescent light.

I see. All you needed was a reduction bushing for the top clamp too. I didn't think it through. Good job.

Thank you. It was a fun little project.

If anyone wants to do something like this let me know. I would be happy to help.

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