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I was going to do a GT250 but now that is shelved for my race bike this year and my old trusty 68 Cobra T500 race bike is now going to become my new cafe project. I am not much on naming bikes other that what they are so for lack of any imagination it will be "Cobra"
Hopefully when I am done with it it will have some bite. The motor will be ported with TR500 heads, Swarbrick pipes, GS500 front end and monoshock rear swingarm from the same. Original 68 Cobra tank with a cafe seat and GS100SZ Katana clipons so far.
How hard was the front end swap? And if you want to upgrade any of the gs500 suspension, check around at GTwins. Seems like everybody over there hates the stock setup.
Had to lengthen the stem about an inch and got bearings that made it a bolt up otherwise. I know the front end is wimpy but I plan new springs and emulators for that. Thanks for the link.
Surprisingly enough, on my other race bike that Frank Melling rode the next year at Dayton, it had two discs on it and would actually do stoppies. Depending on how you set up the front brake, one can be more than enough.
Had to lengthen the stem about an inch and got bearings that made it a bolt up otherwise. I know the front end is wimpy but I plan new springs and emulators for that. Thanks for the link.
Actually I cut it and made an insert to lengthen it. Welded the pieces together. The first time I pressed out the old stem with my sledgomatic and welded in a GT500 stem but didn't like the out come as I felt it was off center and angled wrong.
That's exactly how I lengthened my Stem, cut and weld in a heavy walled tube the proper length and plug weld it. Oh yeah, heavy champfer on the shoulders of the extension tube to get more surface area.
Cheers, 50gary
Well worked on the Cobra (#553 by the way). I got it only as a frame with motor, rear swinger, oil tank, rear fender. I was my old race bike and now a wild cafe.
Delugged the frame and removed the swinger pivot point mounts for relocation of the new pivot point. Just picked up the new "Classic Bike" mag with GT750 vs GS750 and it had an article on frame making. Gave me a little insight as to rear swinger fitment. It was mostly what I was shooting for but a nice simple explaination.
You in effect want a line through the motor, sprocket, pivot point and rear axel when the swinger is under half compression. This is what I was aiming for. I am also using the linkages as they work better than direct mounting. What the linkages do is use the shock for light damping to the half way point and from there it get stiffer under harder exceleration. Direct linkage does not give you this option and revalving of the shock may be necessary to get it to function the way you want.
The way I plan with linkages will allow me later to get a direct fit shock from either of the aftermarket companies makeing them for the GS500.
After I grind off all the slag I will make my cardboard mockups and start then installation process. To allow fitment of the GS500 swinger I will have to cant the motor forward slightly.
Finally got all the extranious stuff off of the frame I don't need to this point. Surely there will be more to come off and of course more to add. The way of the project.
Here is the frame swingarm point before cleaning up.
A couple of pics after the motor was installed and the swingarm set in place near where I want it.
The swingarm as it will look under half compression. This is where I will need to pay attention. The motor is already canted forward to allow more room for the swinger and allow me to angle it properly without chain bind.
A rear view before pivot mounting points are added. Once the pivot point is in place with the swinger, I will work on the rest of the shock mounting.
This is how close the cylinders and heads will be on my engine. You actually have a lot of area here to work with. The small amount you move it forward give lots of adjustment at the rear.
The bottom motor mount will now have to be refabbed as will the rear mount.
I also did some work on the front of the bike. Mainly the headlight brackets and headlight. I want to keep with the vintage look and chose the 1972 GT750 headlight shell and ring. This shell and ring have the squared bottom. The lense itself is a Halogen which will have a 35/35 bulb unless I can find a better charging system. The T500 is weak in that department.
Stock GS500 ears are currently used but don't allow the clipons any movement. I can modify the mounts or get aftermarket types like others use.
Yes, they are quite nice. Had thought of those but was just trying to put it together from stuff in the shop as much as possible. Though want it to look right when I am done.
I assume you rotated the engine about the original front mount point? Interesting to see that our projects are quite similar regarding the new swingarm mounting point. What angle do you intend using for the uncompressed swingarm? You seem to be moving along quite quickly with your project so I will continue to watch your progress, great job so far.
The goal is between 10* and 16* but I won't know for sure until I have all the linkages in place. The shock will have the spring off for intial setting of the swinger horizontal at half compression. From there I will know about where to weld the other mounting points. First I need a complete pivot axel with dust seals and washer to get the width right.
Chain bind is a big concern and will dictate whether the pivot is below horizontal or even.
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