The new longer swingarm

For those not familiar with the purpose of extending the swingarm, I'll try to give a good explanation. The first purpose, which is totally irrelevant in this application, is to keep the front of the bike from lifting during hard acceleration. Since we are not connecting the output of the engine to the rear wheel, this is not an issue. The second purpose is to make the bike handle better at high speed in a straight line. The longer wheelbase makes turns happen more slowly, and will serve to keep us traveling straight and true down the track. One of my shorter explanations to be sure!

Swingarm cut

The first step in extending the swingarm was to cut it and fit in extension pieces. I chose to make the cuts right at the point where the rear of the swingarm made their bends in to the axle adjusters. I then used 1" x 2" rectangular tubing cut to 8 inch lengths to make the extensions.

Extensions clamped in place

C-clamps were used on a work table to clamp the original swingarm pieces and extensions in place so that the alignment would be true and level. Tack welds were then used to get everything temporarily fastened into place.

Finish welded

With everything tacked in place, measurements were taken to insure that everything was aligned correctly. With a few slight adjustments, everything looked good, and final passes were made with the welder. Slightly beveling the ends of the pieces to be welded made for good penetration so that everything will be as strong as the original swingarm without extra supports.

Looks good

With the swingarm extension complete, everything was mounted back on the bike. It looks great, and really makes the bike stand out when compared to a stock swingarm. Now, I just had to figure out how to get the shock completely out of the way of the jet exhaust.

The exhaust solution

To get the stock shock absorber out of the way, it was decided to remove it altogether. This would make the bike a hard tail of sorts, but considering the size of the bike it is the best solution. We could have gone with old style shocks, one on each side, but felt that the appearance of the bike would suffer with that approach. Instead we went with struts that go from the rear of the swingarm up to the underside of the frame where the tank and rear body panels meet.

Room for the exhaust

There is now more than enough room for the exhaust to travel through the frame from the turbine exit and into the afterburner. In fact, this made so much room that we can situate other components under the seating area as well, since the exhaust bends will not have to be so severe.

Battery box location

The area in the front of the swingarm is prime real estate for a battery box. With the tire no longer occupying the space, we can fit two of the PC310 batteries from Odyssey in a custom designed box. The batteries will be able to supply up to 620 amps of short term current, although we will be using a more modest amount in the range of 25 amps for the pumps.

Getting bigger

Compared to the stance of a stock YSR-50, this little bike is getting bigger! The rear tire is about 2 inches off the ground in this photo, but the point is made that the bike definitely sits a bit higher with the mods. Once again, my lovely wife Jordan couldn't help but be included in the pictures. Most guys dream of having their bikes featured on the cover of a magazine with a beautiful model posing beside them. I am lucky enough to be married to the model!

Heim joints

After all this modification, the rear is still adjustable! If you look closely at the mounting point of the strut to the swingarm, you will see that the connection is made with small Heim joints, also called rod-ends. They thread into the ends of the struts, and one end is a right hand thread while the other is a left hand thread. By rotating the struts you can fully adjust the ride height of the bike up or down by over 2 inches. I could have left this out and made them one length only, but the joints were so inexpensive, and looked so neat that I just had to do it. I am sure that it will come in handy later as well. Maybe I will lower the bike for runs down the dragstrip!

Well, that's it for this time. We still need to fit the fairings on the bike and get the lower frame assembly built so room can be found for the new oil tank. Other than that it has been a lot of soldering once again as engine computers are being worked on. Stay tuned, as more updates are on the way! Don't forget to support the site as well, as your donations help to keep the project going.

Russ W. Moore
and
The Bad Brothers Racing Build Team

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