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Old 03-09-2006, 04:04 PM   #54
Ricardo Kuhn
a.k.a. Mr Rico Suave
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Joined: Sep 2001
Location: Salt lake city, Utah
Oddometer: 12,504
Originally Posted by Pezz_gs
Breif Version

Well there are a few things to consider.

The twin shock swingarm was my preference due to Final Drive ratio options

What tyre size are you wanting to run?
First This is all for a R11Engine that i want to build, hopefully that is not a sacriligio

the Rim will be a 18" by 3.75" I beleive from a R11R from wheel, so the tyre will be at the most a 150MM Karro with really spikky knobs

Can you get that tyre in the centre of the bike?
Some of the conversions I have seen have them off to one side by 5 -10 mm 1/2 inch or more.
I have no idea, but i don't see why not..


Do you want to run twin shocks or single shock?
Single, i don't know if mount in the middle of the swingarm or at the end like on this HPN bike with the shock laying sideways (+/- 45 deggres like on the picture)

or maybe a linkage like this drawing i made many eyars ago.


I am going to run a single WP shock of a KTM i have on the shelf.

How much travel do you want? 300mm (12 inches)?
10 will do just fine,i don't think i need more than that, I just need very progresive action so the travel is more useful.

Once you have this worked out you can start building your Jig to extend the swingarm.

Make a Jig up for the swingarm in the stock position and make it strong!!
There will be a lot of force on the swingarm to 'pull' during welding
Allowing for the swingarm to be extended to desired length.

Basically you then have to remove the webing/ Bracing from the swingarm.
Then cut it Just above the cutout for the wheel on the shaft cover (RHS)
Later model swingarms look easier to modify

Then weld in the new section. Might be good to use another swingarm for the same material then brace accordingly.
I'm scare to use the cast aluminum of the estock BMW swingarms, i remenber seeing somewere a guy that cut and paste a section of tube on a stock swingarm(for sure very easy) but the possiblity of a weld fracture scares me far to much, specially after the swingarm failure on my KTM 950 two years ago..
Take your shaft to a drive shaft company with a good reputation. Have them cut and extend the shaft by the same as your extension (100mm)

Hope this helps

Pezz :)
that part is easy, i can get that done in not time, the part that scares me is how to make the cone, the final drive pivot points and also the half moon shape cut at the swingarm to ake the wheel fit..

thanks for taking the time to explain the whole process...oh oviuslly this will be a single sided swingarm
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