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Discussion Starter · #561 · (Edited)
I completed the chain guard. It's a bit chunky and rather boxy looking, but not hideous. It's on there solidly and should be fairly effective.

I constructed it out of 22 gauge sheet steel, backed up with 16 ga. reinforcement brackets underneath. This allowed me to keep the overall weight down, and do most of the bending with my tiny HF bench-top brake (which struggles with 16 ga.) while still being reasonably sturdy. The brackets are are pop-riveted at the top and the mounting screws pass through both layers of metal.

Fitting it up was complicated by the rear mounting boss on the swingarm; it's neither in plane with the swingarm, nor perpendicular to the vehicle centerline. I initially tried to make neat, calculated creases in the mounting arm, but as you can see I ended up having to bend it by hand and pound it with a rubber mallet to get everything lined up properly.

It turned out a bit wider than it has to be, but I'm okay with that. You can see a slight torsional tweak towards the front. I think I might need to slot the hole for the inboard mounting screw to lower that side slightly. Overall, it's not a thing of beauty, but it doesn't suck too badly either.
 

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Discussion Starter · #562 ·
My re-pop Norton Proddie seat base came today. I set it on the bike and the proportions are just excellent. Unfortunately, my initial excitement turned to disappointment when I realized that the seat is nowhere near symmetrical. Looking down the centerline of the bike, it's about as straight as a one-legged drunk with no cane. I must say I'm surprised, as the Reed Titan seat I'd previously gotten from Airtech was perfect. This one is also much thinner, with numerous imperfections and very skimpy gelcoat. They must've had the new kid do this one. I am confident I can make it work, but it will take extra work. I do think the shape of this design is perfect for the bike; I'll post photos once I get it bolted down with the warpage corrected. But after $170 (incl. shipping) and nearly 7 weeks of waiting, I can't say I'm completely thrilled.
 

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Discussion Starter · #563 ·
Thanks to purchase of a dimple die and a bead roller, chain guide 2.0 is turning out much better.

The dimple die is pretty foolproof. There's a definite learning curve to the bead roller, but a few practice runs and a couple of YouTube tutorials helped me get a feel for it.

I bought Eastwood's smallest, cheapest roller for about $100 or so. It's really robust, but fairly crude. It works okay with the bead dies, but there is no positive indexing to prevent the offset flange dies from shifting due to side loads. It's all held in alignment by friction of one 5mm set screw. Fine for my immediate need, I guess.

I have a smaller (1/2") dimple die on the way for more speed holes. And I might try my hand at making an intermediate size on the lathe.
 

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Discussion Starter · #564 ·
Well, that took an unanticipated amount of effort. I finished up the chain guard. It ended up straight and square and surprisingly sturdy, so I am pleased.

I had toyed with the idea of making an intermediate diameter flairing die, but when I realized the holes would mostly be hidden by the rear shock, I decided to just use the half-inch die that I had.
 

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Discussion Starter · #566 ·
You ever want that welded up, mail it to me.
Thanks. Using Pop rivets made disassembling and reusing the brackets with the new sheet metal much easier (which, as usual for me, turned out to be necessary). They’re fine until such time as 1) the bike is running, and 2) these rivets become the ugliest thing on the bike. Alternatively, it could be an opportunity to try my hand at MIG brazing it, but frankly, it’s good enough. I’m trying to avoid getting bogged down in the small stuff. I need to be getting on to the engine rebuild.
 

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im out of my depth here but ive seen bracketry attached to sheet metal by ordinary silver soldering.

im repairing a 1960s triumph sidecover that has missing brackets and ill give it a try
 

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Discussion Starter · #569 ·
I'm super disappointed in the quality of the Norton Production Racer seat pan I got from AirTech Streamlining. I realized it was trimmed rather haphazardly right off the bat, but even taking that into account, I was still struggling to figure out what parts of it were wonky. In order to measure points accurately, I first created a full-size symmetrical template and mounted it on foam-core board.

There's a slight ridge down the center of the tail, so I highlighted that with black marker for my datum line. You can see along the rear edge how poor the cut line is, and how badly the front of the seat corkscrews. [The black marker along the back edge was traced from a template I created using the left side.]

FUUUUUUDGE.
The front is not only not level, but it skews to one side.

This is going to take some real wrangling to make work.
 

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Discussion Starter · #570 ·
I measured points a consistent distance back from the back wall of the seat, then used a contour gauge to transfer the inside shape of the seat to paper. I then created an accurately symmetrical profile on my computer, which I printed off and used to cut a bulkhead out of foam core.
With the bulkhead in place, some painter's tape all around, and a bit of weight, I have the seat pan it fairly well situated. Now it just shows how haphazardly the edges were cut.

 

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wow that's terrible quality.

I wonder if Matt at Tannermatic has anything that would fit the bill?
 

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You have it sitting nicely now. Good look for the bike. It's a shame about the quality, I had understood Airtech stuff was well made.
Really like the tank colour. Did you say what it was somewhere in the thread?
 

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Discussion Starter · #574 ·
You have it sitting nicely now. Good look for the bike. It's a shame about the quality, I had understood Airtech stuff was well made.
Really like the tank colour. Did you say what it was somewhere in the thread?
It's a reproduction tank I bought from India. The color is "cherry red," according to the description, but I doubt it's even trying to be a genuine BSA hue. I plan on getting it color matched, but I am going to reverse the base color and accents on the other body parts to hide any mismatch.

 

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Discussion Starter · #575 · (Edited)
I've never mounted a fiberglass seat before, so I might be going about this all wrong, but I knew I needed to add some sort of additional structure under the seat to support for my weight. A wooden block seemed a bit kludgy, so I bought some 1" thick HDPE marine board. I first cut it to just fit inside perimeter of the seat area. I then went to work on it with my router, using a 1/2" rounding bit on the topside to match the inside curve of the seat edges.

I flipped it over and used a 3/4" half-round bit on the bottom to create pockets for the frame rails. The marine board was thick enough to show below the edge of the fiberglass, so I used a square bit to bring the outside level with the top of the frame reliefs.

I didn't like how wide the seat pan was at the front; it's wider than the back of the tank which makes it look mismatched. So, I cut the seat base a bit narrower at the front, matching the angle of the frame tubes.


I'm really pleased that the fiberglass is fully supported to the edge by the HDPE. I can trim the corners off the seat base without losing any structural integrity and having the front if it get all floppy.

I am probably overbuilding this, but I've seen too many fiberglass parts that cracked due to excessive stress. The only downside this is the weight. It's a seriously heavy board, but I will add some lightening holes to the center to remove some of the weight before it goes together.

While I was in the garage, I swapped out the 7" bucket for a 5-3/4" headlight and a Kawasaki AR80 fairing I bought a while back. I thought the number plates on the side might look out of place without a fairing, but after sizing them up, I decided I'm just going to stick with a naked front and the larger headlight.
 

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Discussion Starter · #576 ·
104030

In other news, I bought this frame from an SST/Panther DB175 off Ebay yesterday. We've been talking about engine swaps a lot on the podcast lately, and I'd been casually looking for an inexpensive frame for a lightweight 2-stroke "special." My criteria were:
  • single top tube, so you can slap any old chopper tank on it;
  • fairly widely splayed twin front downtubes, which facilitates exhaust routing on a single and simplifies front motor mounts;
  • all tubing, with no stamped steel sections;
  • no central downtube between the the back of the engine and swingarm, which limits the choices of both of those components.
It all adds up to something super easy to re-power and swap parts onto.

The seller originally listed it at $179. I put it on my watch list when he dropped it to $125, and when he sent me a private "special offer" of $93.97 including shipping, I couldn't pass it up. With Bultakenstein and the Ducati-Aermacchi Special already in line ahead of it, I may never get around to this. But, hey — for less than a C-note out-of-pocket, I can hang it in the rafters and dream. Thanks to all the stuff I've tried for Bultakenstein, I already have a cache of chassis components and bodywork that will likely work with this.

As far as engine choices go, Yamaha's Blaster motor probably tops the list. It's a fun, compact, air-cooled two-stroke that's modern* enough to cheap and plentiful and still have great parts support. I also have a spare Bultaco 200 motor waiting for a rebuild, but that was designed to go in a single-downtube frame; it would likely have clearance issues due to its offset exhaust port. A four-speed 360 would be awesome, but parts are getting pretty scarce (and thus, expensive). There are plenty of other potential ideas, such as a watercooled 80 or 100 cc MX motor, or even a Predator motor and CVT. I'm not worried; if I keep my ear to the ground, something cool will drop in my lap eventually.

*"Modern air-cooled two-stroke" — is that an oxymoron?
 

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Discussion Starter · #577 ·
Continuing with the seat. After I took these photos, I temporarily spray-glued three sheets of 1/2" polypropylene packaging foam to the seat and trimmed it with a hot wire cutter. I plopped my butt on it and I was really pleased with how it felt. The rider triangle is definitely compact, but not uncomfortably so.

 

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View attachment 104030
In other news, I bought this frame from an SST/Panther DB175 off Ebay yesterday. We've been talking about engine swaps a lot on the podcast lately, and I'd been casually looking for an inexpensive frame for a lightweight 2-stroke "special." My criteria were:
  • single top tube, so you can slap any old chopper tank on it;
  • fairly widely splayed twin front downtubes, which facilitates exhaust routing on a single and simplifies front motor mounts;
  • all tubing, with no stamped steel sections;
  • no central downtube between the the back of the engine and swingarm, which limits the choices of both of those components.
It all adds up to something super easy to re-power and swap parts onto.

The seller originally listed it at $179. I put it on my watch list when he dropped it to $125, and when he sent me a private "special offer" of $93.97 including shipping, I couldn't pass it up. With Bultakenstein and the Ducati-Aermacchi Special already in line ahead of it, I may never get around to this. But, hey — for less than a C-note out-of-pocket, I can hang it in the rafters and dream. Thanks to all the stuff I've tried for Bultakenstein, I already have a cache of chassis components and bodywork that will likely work with this.

As far as engine choices go, Yamaha's Blaster motor probably tops the list. It's a fun, compact, air-cooled two-stroke that's modern* enough to cheap and plentiful and still have great parts support. I also have a spare Bultaco 200 motor waiting for a rebuild, but that was designed to go in a single-downtube frame; it would likely have clearance issues due to its offset exhaust port. A four-speed 360 would be awesome, but parts are getting pretty scarce (and thus, expensive). There are plenty of other potential ideas, such as a watercooled 80 or 100 cc MX motor, or even a Predator motor and CVT. I'm not worried; if I keep my ear to the ground, something cool will drop in my lap eventually.

*"Modern air-cooled two-stroke" — is that an oxymoron?
I bet a KTM 2-stroke motor would fit in that.
 

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Discussion Starter · #579 ·
I'm working on upholstering the seat for Bultakenstein. For the foam padding, I am using 1-1/4” thick yoga mat I bought off Amazon. I also bought some pre-made diamond-tuck quilted vinyl for the seat face and standard black marine vinyl for the sides.

To put it all together, I bought a Chinese cobbler’s sewing machine for $110.


The tripod stand that comes with these machines is really poor, so everybody makes their own custom stand. Since I don’t have a lot of extra space in my workshop, I simply bolted mine to a thick 90-degree angle bracket I can clamp in my vice. It was quick, cost me nothing, saves space, and holds the machine securely.


It took a bit of tweaking, but I eventually got it running well, with smooth stitching and nicely balanced tension between the upper and bobbin threads. In this photo, the red thread is sewn through four layers of the marine vinyl.


I have trimmed the foam for the bottom of the seat and I’m currently working on a pattern. I have another piece of foam that will fit against the back of the seat cut-out that isn’t shown in this photo.
 

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Discussion Starter · #580 ·
I've made some progress sewing the seat cover; the front half is done. It looks okay, but the bottom of it is a bit wonky. I'm not completely sure where I mismeasured. Fortunately, it's smooth and symmetrical from above, so it doesn't look horrible. It's good enough — after all, the entire bike will be a "20-footer." I initially chose red thread because I planned to add a contrasting top stitch around the seams, but I've decided to skip that, at least for now. I'm deliberately making it a snap-on cover, so it won't be hard to recover it at some later date, after I've got it up and running. Of course, I might still totally screw up the back half and have to start over.


 
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