Project CB690 (KTM 690 engine in a CB550f frame)

Hydraulic brakes shouldn't be a problem, but manual drums set up like that - if the torque stay should give any, it just grabs the brakes harder. I enjoyed a 65 mph slide down Folly Beach Road in the mid '70s from that.
 
The bike is all back together and ready for a test ride. However the weather is pants so went on to some other projects. The radiator trim needed doing. I got some 38mm wide aluminium that has a curved profile, and just cut and rounded the ends. This will be painted black later. I also got an OEM Suzuki radiator screen and side cover bits in an auction. I had to modify the side cover bits, as they are now top/bottom cover bits. All's good, I'm happy with it. Also need to mount the horn somewhere, and a number of other small tasks. As soon as it stops raining I'll go do a shakedown run and test the shortened swingarm.
 

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That's a really nice torque arm, but torque arms are best in tension mode. If the load causes it to twist or bend, it can result in a locked up rear brake. The simplest set up is located on a peg in the swingarm, but if it needs a torque arm, it's better to have it in tension.

We had an RS125 racer years ago with a skinny little torque arm (in tension). The early GS 4 cylinder Suzukis used a 3/4" tube in compression, but a large diameter tube can handle more twisting/bending load than a thin rod. The larger the diameter, the greater the load it can carry, so a large diameter tube is stiffer than a small diameter rod.

How as the caliper retained on teh KTM wheel/swingarm combo and can that be replicated.
 
I've been reading your CD175 project with interest, even made a couple of suggestions, under the user name I M Band. This was a dig at Vertical Scope, who banned me for posting links to the new independent Vintage Honda Twins site, where most of us long time Honda Twins members moved to, following disgust at the way VS were / are running the original HT site. It'd be great if you'd look in at us over at VHT, all the old crew are there.
 
Ok well it's been over a year, it is finally time to do the full teardown. In the past year I've put about 50 miles (at most!) on the machine. I wanted to ride it and get to know it, so when it came time for the teardown I would have a good idea of what needed any fixing/adjusting, but everything has been pretty evident from the beginning.
The plan for the bike is as follows:

  • Address the things that need to be changed while the bike is still assembled.
    • Chain guard
    • Front computer mount revise
    • Horn mount
    • Centrestand
    • Sidestand switch revise
  • Tear the bike down
    • Put everything in piles
      • Parts to be generally cleaned
      • Parts for beadblasting and painting
      • Parts to be replaced
      • Parts to be modified then cleaned and or painted
  • Order all parts needed
  • Modify and finish anything else
    • Swingarm finish cleanup
  • Fully weld the frame. There a lot of m6 nut inserts and mounts and things that need finishing.
  • Drop the frame and swingarm off for beadblasting/powdercoat
  • Repaint the engine
  • Paint the tank/sidecovers/headlight shell
  • Finish cleaning, modifying, and painting all parts
  • assemble
  • Test
  • Ride the bike, document with professional pictures, videos, update this blog
  • Try and get the bike onto bikeexif or the like
  • Sell.
I've decided that I enjoyed creating the bike more than I like riding it. I don't want to park it in the garage and watch it slowly rust and deteriorate, it would just make me feel guilty for not riding and enjoying it. I'm into this bike for about £12,000 already, I will entertain serious offers.

Ok. So here we go. Over the last bank holiday weekend I started. Here is the initial state of the garage and the bike.
 

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I didn't document all this very well at the time. I mounted the horn by creating a tab off of the front engine mount. Next was the front computer mount. Below is the before picture, the after picture will have to come later! Also I changed the muffler mount. I had only tacked on the mount to the frame, but wanted to change it to a solid mount all the way down to the muffler. Then it will be part of the frame and it will be less visually distracting than a stainless mount.
 

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Currently the centrestand has no stop, and no spring. They will have to be revised since the new shorter swingarm doesn't allow them to be in their original locations. Below I've just mocked up where the stand will be stowed so when the bike is apart I can make a stop.
I am in the middle of deciding whether I actually want a centrestand at all. It looks a little awkward and it may be a lot of work to go through for something that the future owner may not even want. I will have a think about it.
 

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Rear brake return spring. It is a tube that is mounted to the body of the master, and the rod rides inside it. It works really well and is tidy, I'm happy with this. Note how rusty the rear brake got because I neglected to throw a coat of paint on it. I was expecting to do the frame teardown a YEAR ago.
 

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Teardown commence.
 

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Appreciate your thoughts on this one. I made a chain guard from some aluminium coping. The whole thing will be painted black in the end. I made some brackets but after assembly I could get the chain to touch the guard, so I made some new brackets, and now it seems to sit really high. Does it look weird? Should I make it lower?
 

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Frame outside for final cutting and sanding in prep for welding. The swingarm and engine await their turn.
 

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Parts organised on the shelves, awaiting the turn to be cleaned or painted.
Probably no work this weekend due to a visitor, will finish the frame hopefully the weekend after. Current lead time on powdercoat is 3 weeks.
 

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Almost a year between posts!
Where did I leave off? I had just totally disassembled the motorcycle in preparation for frame powdercoating and essentially a total rebuild and refurbish, then I had to go to America for 3 months for work, then a bunch of other stuff happened, then it was winter, and here we are. I completely forgot everything and now I have to remember what it was that I was doing a year ago.
I am considering painting the engine. I am also considering NOT painting the engine. I am considering vapour blasting the covers only, giving them a scotch-bright finish, and leaving the paint on the engine. Either way, the engine will need to be cleaned up, so I made an engine stand out of scrap parts. The rectangular tube was actually previously used on the the frame jig, in the last picture you can see the headstock support. DO NOT look at the welds! I tig tacked everything together, and then MMA welded all the joints for a little practice and to save my argon. It did not go well. But, it works, and is good enough. While I was at it I made the engine rototable.
So next I will clean up the engine, decide on the paint, and execute. Meanwhile, the frame has some last final bits to weld up, then it is off to the powder coater. He will also get a box of parts for bead blasting/vapour blasting. Then the wheels will get new tyres. Then, it should all come together at the same time, and will get built up into a rolling chassis. Then all the other parts get cleaned, refurbished or replaced, and installed on the roller. AND THEN,, the tank paint. Then I will be done.
 

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I did some testing with paint stripper just to see if the paint magically came off, it did not. I think it is powder coated because the stripper didn't even touch it. No matter, the determination has been made. I will just clean up the engine the best I can, and vapour blast the covers. I'll probably give them a scotchbrite finish and clear coat them for protection.
 

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