There are many ways to lengthen a TY175 swingarm but I decided to make new, longer axle mounting plates from 6mm x 50mm mild steel strip and weld them to the stubs of the existing axle plates. This avoided having to make new shockie mounts. Its probably not obvious in the photos, but the centre line of the new axle slot is lined up with the centre line of the swingarm side arms, which is also the case with the original axle slots. The length of the new axle slots and the location of the cam stops relative to the slot ends is also the same as for the standard setup. I made a cardboard template of the new axle plates, sized to have the axle slot 45mm further back than standard, and marked the cut line on the existing plates. I made the new axle plates from the template, carefully making them exactly the same shape and size and slot position. I ground a vee on one side of the new axle plates, cut the first axle plate off and made a matching vee on it. I then tacked the first new plate in position. I then ground a vee weld prep on the other side of that joint and welded it. I then welded the other side of the plate.
I used a flat surface and a dummy axle to make sure that the second plate was going to be positioned exactly right and welded it on.
I then welded on the cam stops, made from the shank of an 8mm steel bolt.
The brake plate link is now too short so I am planning to make a longer one. The brake rod may be long enough as is, as I have rotated the brake arm on the spline. The chain needed a few extra links. The rear frame loop needed to be bent up a bit to provide tyre clearance at the rear end of the guard.
I've ridden it since the mod and there is more weight on the front end as expected and the stability when turning uphill is much better. I can tell that the front wheel needs a wider arc in tight turns but it is still taking a smaller arc that my non-TY175 1970s twinshock trials bikes. The longer swingarm has also increased the travel of the rear wheel slightly, which has softened the rear suspension action nicely.
Edited by feetupfun, 29 January 2011 - 08:56 AM.