HOW TO: Brace Your Swingarm
You'll need some scissors, some stiff paper, some pva glue and glitter...Kidding...
This guide is for painted swingarms, but it will work on the 98-01 if you know a good alluminium welder. There are no pictures of the processes 'cause I didn't think to take any, there are pictures of the finished product, and you'll get the idea when you look at your swingarm.
Remove the wheel and chain if you plan to leave the swingarm in the bike until you're ready to weld. You'll need some clear contact (adhesive book covering) and a fine permanent marker. Clean the swingarm with metho. Stick a piece of contact to the swingarm. Get it to stick as close to the radiused edge as you can, try not to get any wrinkles. Cutting off the excess contact will help. Trace around the inside of the hole (on the sticky side of the contact) with the marker. Don't worry about the leading edge of the left hand side where the chain goes through. This comes shortly.
Next you'll need two pieces of raw aluminium sheet, NOT anodised. They need to be 400mm x 200mm for the '04-'06. I used 2mm thick sheet, much thinner and it's hard to weld without melting through, much thicker and it's hard to shape. Stick the contact with the outline to each sheet. Now you can draw the leading edge of the chain hole, don't worry if you don't get it right first time, wipe the marker off with metho and try again. Be aware of the linkage bearing in the center front of the arm. If you cover this up it will hard to replace this bearing. You may also run out of room for the chain, if you go too much further forward than this. Now cut the shapes out on a bandsaw, if you dont have access to one, find some one who does, or ask a metalworking shop to do it for you. Now is a good time to look out for a competent aluminium welder too. NOTE: When you cut the shapes out, cut at least 3 mm outside the line so that you have room to work with.
Now it's time to shape the plates, both the edges and the curves. This is the hard part, and it's worth taking the time to get the shapes as perfect as you can. I used a linishing belt to shape the edges, but an angle grinder with a sanding "flap" disk will do. Make sure you have a bucket of water near by, it'll get hot real quick. I used my knee and various different bits of pipe to help me shape the curves on. You can mostly push the plate with your hands, but if you go along the chain and around the radius of the lower brace, you'll need a hide or wooden mallet to shape tighter curves with. You have to shape the outer edge as you shape the curve, because you can't tell what size the plate should be, until its the same shape as the swingarm. Keep at it, it takes time but you'll get there. NOTE: The plate should rest on the radiused edges of the hole in the swingarm, for the most minimum weld. Don't take too much off the outsides, you dont want the plate to fit inside the hole, you want it to be flush with the surface of the swingarm.
Now remove the swingarm and everything connected to it. Remove the spindle sleeve from the pivot bearings, and clean the pivot point outside edges with solvent, to remove all grease. I used xylene. Then mask the pivot points well, with several layers, to protect the bearings. There is a ridge around the pivot ponts where they are machined by the factory. mask up to these ridges.
This is where the metal workers and the NOT part ways. If you can't do this yourself, go back to that metalshop you found and make some freinds...
Now you need to prepare the swingarm for welding. I cut a piece of 60mm pipe, 5mm wall thickness, slightly longer than the space between the arms. Then I squared up the ends in a lathe and got it the exact length. I put the pipe in between the arms, put a thick 50mm washer in the axel cutouts, and bolted it together with a 16mm threaded rod and nuts. This stops the swingarm from both twisting and expanding when you weld it. Now heat the arm up with a jetfire gas heater,(or similar) untill it's too hot to hold but not too hot to touch. Sand the paint off the edge and 20mm on each side, only sand the side you are about to weld, this prevents aluminium oxide forming and breaking the arc. I used a MIG welder because it is quicker and cooler than TIG. Tack the plate in, on the out side of the arm, with 50mm between tacks. Then go back over and fill between the tacks. Don't build the weld too much because most of this gets sanded off later. Then fillet weld inside the swingarm. This is the actual stong join between the plate and the arm. While it's all still hot, turn it over and repeat the process on the other side. Then, still hot, sand off the excess weld on the outsides of the plates. I used a flap disk to get within .2mm of the surface, and a disk sander to finish it off. Now let it cool right down and remove the axel spacer.
Next up is prep and paint, I gave both these jobs to professionals. I got the swingarm bicarb blasted because it gives a silky smooth finish for the painter. Sandblasting is too coarse but there are other abrasives available, check with your local blaster for the smoothest finish you can get. When you give it to a painter, make sure he plugs all the threads and holes to protect the threads. And get him to mask up the linkage bearing and dust seals, if you don't intend to replace them. My painter used a black JOTUN epoxy filler to get the suface right. This is used on ships hulls before paint, and is very hard and corrosion resistant. The fillet welds inside the swingarm were coated with SIKA paintable sealant, to keep water and corrosion out of the weld. The arm was painted black, given a very fine mist of silver, and finally a 70% gloss clear coat. It helps a lot if you can provide a sample to get the paint to match the frame perfectly. You can often find destroyed or damaged subframes and swingarms at a wrecker that you can borrow or cut a sample off of.
Finally you can put it all back together, this is the best bit, try not to get too excited and damage something. I used this opportunity to replace or repack my bearings with grease. You can do the shock , linkages, pivot and axel as well as cleaning those rarely seen places. It'll make you feel better.
Good luck, get modifying.
Last edited by CARBONAR1; 09-20-2009 at 05:15 AM.