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Discussion Starter #521
My father-in-law was a research chemist. One of his favorite aphorisms was, "In theory, there's no difference between theory and practice. In practice, there is."

It turns out that my design for the the threaded-together cross-shaft is fundementally flawed. Pushing your foot down on the shifter can exert a remarkable amount of torque. Instead of a nice, positive stop, the limit of pedal travel instead devolves into an indistinct, mushy feel as threads begin to distort. After a number of upshifts and downshifts, either a) one of the threaded studs backs off and the whole assembly goes loose, or b) the lever rotates so far out of its original alignment the other way that the mechanism binds before upshifts or downshifts occur.

I tried adding blue Loctite on the threads; it might as well have been apple butter for all the strength it added. Then I tried a dollop of JB Weld in the bottom of the internal shaft threads, thinking that would provide more positive resistance for the studs and magically stop the thread deformation. That was utterly ineffective, and one of the studs broke free within a few gear changes. So, as of right now, the whole shaft is basically glued together with red Loctite 271 — effectively turning the self-aligning flange bearings and shaft into a single, non-disassemblable unit. I'm letting the Loctite set-up and cure for a couple of days before I really mash on the shift lever, but I am confident the whole thing will eventually need a re-design. Maybe this would not be an issue if I were dealing with a new Japanese bike that has a slick-shifting, low-effort, extremely precise shift action. Bultacos, however, are cantankerous, stone-age things with high-effort, balky shifting that requires a LOT of pedal travel. It might work marginally smoother when the engine is running and the transmission shafts are turning, so I am going to continue with the next steps and revisit this once I have a running machine, but I expect to revisit gear selection at some point.

[IMG]

Here you can see a whole raft of index marks on the backing plate. Between upshifts and downshifts, I need the whole range of travel between when the rear of the pedal hits the footpeg and when the front rose joint binds against the bracket going forward.

[IMG]

The bent-up linkage between the lower arm and the stub of the original shifter is just a quickie proof of concept. The real component will be an alloy clevis threaded to a spherical joint at the bottom, which should eliminate some free-play.

[IMG]

I had to re-bend the shift pedal just so. I discovered that there's barely enough clearance for it between the arc of the kickstarter and the shift linkage, but it all clears as it's positioned now.
 

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Discussion Starter #524 (Edited)
This morning before work, I made up the clevis for the right-side shift linkage out of 6061-T6511 alloy 3/4" square bar stock. The upper end is attached to the Bultaco shift lever using a socket head shoulder bolt (5x0.8mm thread, 6mm shoulder dia.). On the other side is the original rose joint that came installed on the Ducati stub arm I'm using for the lower linkage. It still needs filing and polishing, but there is no noticeable play, and the geometry of the linkage arms is much improved. Even without the shaft bearings installed, I can already tell this will work much more smoothly and precisely than my earlier mockup.









I am still working to resolve my shaft-spline interface issues. I think the ends are good candidate for brazing, rather than welding. I ordered some MIG brazing wire, so I will see if my little Clarke MIG welder is up to the task once that arrives. I have not decided whether to simply braze the ends on with the flange bearings already on the shaft (at which point they will become no-removable), or to go with some sort of (as-yet undetermined ) split bushing arragement. I have some Delrin stock coming this week, but I am not sure I will go through the hassle, especially if the brazing wire gets here first.
 

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Discussion Starter #525
After letting this shift shaft cause me bunch of unnecessary headaches — playing around with all sorts of solutions such as split bushings, pinned joints, and the like — I finally decided to use the KISS method and simply have the splined ends welded onto the shift shaft with the existing flange bearings already on it. A quick trip by my favorite local welder and I'm in business.


The bearings are now non-removable, which is admittedly a little bodgy, but in reality it won't make any difference. After all, having bearings as a captive part of a larger assembly isn't unheard of in the engineering world and, given this bike's experimental nature, the chance this linkage ever getting sufficient use to warrant replacing these bearings due to wear is a pretty far-fetched notion. At whatever future point these bearings are no longer serviceable, I am sure the bike itself will have been long-ago disassembled, or a rusty and corroded hunk lying in a field somewhere.


BTW, the discoloration on the shaft is NOT excessive HAZ from the welder. I'd previously blued the ends using a polypropylene torch to un-do the red thread locker.
 

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All you'd have to do to replace them is cut the end off and re-weld it back on once done. Super easy, barely an inconvenience.
 

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Discussion Starter #528
I got the fuel tank mounted. In British fashion, the BSA OIF Export tank is designed to be secured by a central mounting bolt. Rather than permanently weld a stud or bracket onto the frame, or modify the frame further, I decided to utilize the unused bosses I'd originally added for mounting the rear shock, back when I was messing around with a monoshock arrangement. I bent up a bracket out of 18 ga. galvanized steel (the thickest my dinky HF brake can bend).



I realize that using four M8 bolts to mount a bit of light-gauge sheetmetal is slightly absurd, but in the immortal words of Nik Blackhurst, "Overkill is my second favorite kill."
The tank rubbers at the front and rear are standard BSA issue, however the tank needed to be raised significantly at the back. You can see the two strips of thick rubber I added to the rear mount. A length of threaded rod runs down through the three pieces. Also, since my backbone tube isn't quite as large in diameter as the OIF BSA-Triumph frame, I need a tiny bit more width. The stick-on weatherstripping actually does the trick perfectly, but I might try to come up with something else just to make it less amateurish looking. The two rubber bumpers on the bottom mount are non-BSA-spec, just to keep the tank from rocking side-to-side.



To keep the sheet metal from deforming when the center bolt is tightened, there's a thick steel backer plate between the bolt head and the box. The hole for the bolt is threaded, to lock the bolt and keep it from turning when the top nut is tightened.



It all needs a bit of tweaking to be perfect, and I need to get some new, proper hardware for it, but once the center bolt is cranked down it's not going anywhere, and it looks good.
 

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Discussion Starter #529
Well, with the pegs and foot controls sorted, and the tank mounted, I went looking for another excuse to NOT begin rebuilding the engine. The front forks are from an '82 GS750E, and the front wheel is from an '81 GS850GL, both of which had two single-piston calipers clamping twin 276 mm rotors. The logical thing would be to just mount the stock brakes. But I figured I should see what front brake setup might be possible from the brake components currently in my parts cache:

The mounted disc is from an '84 GS550E with a 16" front wheel. It fits, but it's 260 mm diameter.
The disc at right is from a '76 GT550. It will also mount to my wheel, but it's 292 mm dia. and 6.5 mm thick.
The disc at the left is from a Kawasaki BN125 Eliminator. (It has nothing to do with this at all, but it was on the shelf. Why I bought it, I'll never figure out.)

Perhaps one of these discs could work with the right caliper?

Cockwise from the top right:
  1. 4-piston from some Yamaha sport bike. I didn't bother going back to look up the year and model because its opposed-piston, monobloc design is much too fat to work with my wheel and forks.
  2. Grimeca 3-piston caliper from an Aprilia Atlantic 500 maxi-scooter. It is actually a pretty promising candidate, but since it was used in a linked brake system in its OE configuration, I'd have to do some figuring-out on the proper diameter master cylinder to match it with.
  3. Yamaha V-Star 250. Small, twin-piston caliper isn't known as a super powerful option, but it's lightweight and would probably be suitable to a bike of Bultakenstein's mass. (Although the bike keeps getting chonkier with every overbuilt bracket I fabricate.)
  4. Single-piston rear brake caliper from the off a Suzuki Vinson 500 four-wheeler. I bought this to replace a Honda CB125 mechanical caliper. It has no business on the front of this bike.
  5. Suzuki GS650GL. This came with the first set of forks I bought for this project, and the caliper itself should work. However since its off a cruiser with leading-axle forks, the hanger bracket it's on won't work with my forks.
If I wanted to make a custom adapter bracket for the Grimeca, V-Star, or GS caliper, I could make any of them fit the forks and work with one or both of the rotors I have. However, after looking everything over, I decided that that'd be too much unnecessary bother. There are plenty of of Suzuki brake parts out there that will bolt up. Since a single disc is more appropriate to this bike than twin stoppers, I narrowed in on the brake from a GS450 or GS750T; both had a single disc that utilized the same caliper carrier bracket as the GS750E, so I know it will fit my forks and have a properly sized master cylinder. I found this complete but molderin' setup for under $40 shipped on Ebay. It should arrive in a couple of days:

It may or may not be rebuildable; I'll find out when I examine it in person. However, I have the option of keeping the hanger bracket but swapping out the caliper itself for slightly earlier iteration from the the GS650GL. The master cylinder and brake hose are, at a minimum, mockup patterns that will help me determine what length line and piston diameter I need to source.

Speaking of mock-ups, while I was shuffling parts around the shelves, I pulled out the prettier, re-pop tank and bolted it in place of the derelect BSA original I've been using as a stand-in. I also put the original Alpina head on it, since I probably won't try to adapt the radial Husqvarna head until after the bike is running. I have to say that the stock head looks dinky by comparison.

Ever since I had the rear of the frame welded up, I've been itching to see how well the seat from a Norton Production Racer would work on this frame. The Reed Titan seat I bought earlier fits well and would work just fine, but something about it feels slightly "off." (My guess is that it has to do with how far forward the top shock mounts are.) I also discovered that the R-T seat works much better on the Aermacchi-Ducati Special. Well, I recently sold my TIG welder, and splurged with some of the proceeds. I ordered a "Proddie" seat from Airtech Streamlining. It won't show up until after Halloween, so in the mean time I photoshopped a wild-ass guess of how it might look on the bike. I scaled the two source photos as accurately as I could, but it could be way wrong. I might have to invert the shocks—Marzocchi Strada style—if they're in the way of the number plate. But if this works, I think I'll like the overall appearance much, much more. Originally, my title for the build thread going to be "Creatively placing parts in close proximity," and that's exactly what it was for years. Lately, though, it's gotten closer to being a complete bike!
 

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Just an observation:
Seems like everybody that fits bump stop seats are putting them behind a short tank. If you look at a real bump stop seat your bump should be nearly over the rear axle, it's not suppose to shove your knees forward into your elbows.



(y) carry on.
 

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Discussion Starter #531 (Edited)
Just an observation:
Seems like everybody that fits bump stop seats are putting them behind a short tank. If you look are real bump stop seat your bump should be nearly over the rear axle, it's not suppose to shove your knees forward into your elbows.



(y) carry on.
I see your point. The way I am using it doesn't seem too drastically different than its original placement, as far as being forward of the rear wheel, but the Norton admittedly has a much longer reach to the bars. If it ends up being too cramped, I can always go back to the Reed Titan seat, or shift it back more and 'glass in an extension at the front of the seat.

And, hey, I'm thrilled to get any feedback on this. This site is so dead, I was debating whether or not to keep updating this thread at all.

103873


Ergonomically speaking, I'm thinking it will be more like...

103875


103874


103876
 

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;) the Norton had a slightly longer wheelbase.
Really depends on the rider but I like to be able to shift my weight back on the bike further, I don't want to be humping the fuel tank All the time ;)

**** em I read ever post
 

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Just a thought Tanshanomi, these Jota style bars might help getting the riding postion you're after.
I tried them some time ago and they worked a treat.
100_0145.JPG
 
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Discussion Starter #534 (Edited)
It turns out that my slotted rotor is actually 276 mm, which is what I need. So, I have all the components I need for a complete GS250T/450/750T brake setup.
BTW, here's all the models that used these identical front brake components. (I realize you don't really care, but I'm including it here because I refer back to this thread as a record of the research I've done.)

The caliper, hose, and master cylinder I bought off Ebay arrived, and the components are generally as borked as I expected them to be from the photo.
The slave cylinder is a total write-off, as are all the rubber and plastic parts.

Fortunately, the alloy caliper body is still in good shape, with a bore that's smooth to the touch. A new OE piston, seal, and boot are on their way. I also included a new bleeder screw and cap, because the existing one is rusty and it was easier to just order it than try to clean up the old one, or source it elsewhere. A bit of time in the ultrasonic cleaner and perhaps a light touch of Scotch Brite in the grooves should be all that's needed to bring it back to serviceable condition.

It's a good thing that this caliper is salvageable, because I discovered that the Aisin caliper I'd picked up previously won't work in this carrier; the bolt centers are the same, but the Tokico and Aisin have different diameter slide pins.

I don't have any photos, but I also disassembled the a master cylinder. It wasn't as badly corroded, but wouldn't pump fluid. Suzuki no longer sells the rebuild kit, but I ordered an All Balls seal and spring kit, along with a new sight glass. Rebuilding will cost me significantly more than just buying a new, generic knockoff master cylinder (under $20 from any number of Ebay vendors). But 1) I have to believe the tolerances and metallurgy will be a bit better with the old OE Suzuki parts than an no-name Asian cheapie, and 2) I want the practice. I've rebuilt brake parts before, but not for several decades, and this project is all about gaining skills and experience, right?

As a backup, I also picked up this Aprilia master cylinder from a 2009 Dorsoduro, mostly because it was dirt cheap. It's the same 14 mm piston as the Suzuki, and it came off a (supposedly) functional bike.

It will be a week or so to get all the parts I've ordered in, and the new seat is still a couple of weeks away.
 

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Discussion Starter #535 (Edited)
After 20 minutes of ultrasonically lounging in a solution of Simple Green and L.A.'s Totally Awesome, the brake parts came out surprisingly spiffy. I'm sorry I didn't take "as opened" images: they were naaasty! A few bits need some remedial de-gunking in the crevices, but I'm happy with the result. I'm confident the parts that are on the way are all I'll need to have a safe, effective front brake. The rusty-headed bolts not in the photo went into a cup of Naval Jelly.

I can't say this strongly enough: if you don't have an ultrasonic cleaner, you don't know what you're missing. Get the biggest, best quality ultrasonic cleaner you can afford. I bought this one on closeout from Grizzly, and it's excellent.
 

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Can't disagree about the ultrasonic cleaner, did you use distilled water in there?
 

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Discussion Starter #539 (Edited)
103888

Seriously? Well, that's not good.
Luckily, I've sourced another one via Ebay — assuming the dealer that listed it actually has it in stock already.
It just demonstrates how parts are drying up for older Japanese bikes, even items you wouldn't think expect to be a problem.
 

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couldn't you (not sure on cost) just have some new ones machined from stainless stock?
 
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