Bride of Frankenstein - a cure for leftover parts cluttering the workshop.

Tanshanomi

Well-Known Member
Nice work... Like your avatar too. Do you actually have a Mercurio in your collection?
Nope. I'm on my fourth Bultaco at the moment, but never owned a Mercurio, or any Bul street bike. I've always wanted to create the big-bore roadster Bultaco never built, so...this is "Bultakenstein," my current mongrel project. The only Bultaco parts are the front 2/3rds of the frame and the engine. The salvage lump that's in there will eventually be replaced by an 350 Astro flat-track motor that a pro is currently building for me. Which should keep things interesting.

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DaddyJohn

Well-Known Member
Nope. I'm on my fourth Bultaco at the moment, but never owned a Mercurio, or any Bul street bike. I've always wanted to create the big-bore roadster Bultaco never built, so...this is "Bultakenstein," my current mongrel project. The only Bultaco parts are the front 2/3rds of the frame and the engine. The salvage lump that's in there will eventually be replaced by an 350 Astro flat-track motor that a pro is currently building for me. Which should keep things interesting.
Looks like Suzuki GS450 wheels…:)
Maybe a BSA OIF tank?
 

Tanshanomi

Well-Known Member
In preparing to tack-weld my fuel tank bracket to the frame, it was apparent to me that once the fuel tank was in place, even slightly inaccurate placement would get magnified into noticeably wonky misalignment of the tank. The correct approach is to first get the tank positioned correctly, relative to the frame, and let that dictate the precise alignment of the bracket. Before welding anything, I had to make up the rest of the tank mounting hardware. Mounting this tank to this frame is slightly problematic. The late ’70s Can-Am Qualifier this tank comes from had a very large frame backbone. Furthermore, I’m mounting the tank much higher on the frame than the original application. As a result, the gap between my frame and the tank tunnel is significant, requiring some large spacers. Since the angle of the tank tunnel and the backbone of my Shin San Tong frame are different, the space under the tank is greater at the rear than the front.

With a plastic tank, whatever touches it has to be softer than the tank material itself, to avoid abrading the plastic. Many years ago, I bought several rolls of 1/2″ thick, 4″ wide, medium-density nitrile rubber. I’m guessing it’s durometer is about Shore 70A. It should be perfect for this application. I decided to use two pieces of rubber, mounted vertically: one at the front and one at the rear. I did some measuring and eyeball-engineered the shapes I needed.

Rubber of this density is typically pretty hard to cut accurately. Using a razor or Xacto blade usually results in a series of jagged slices. A scroll saw can work well — but I don’t have one. However, since the forward rubber block is basically round, what if I used my lathe for that one? It was worth a shot. I cut a piece of nitrile sheet to the approximate size with a hack saw, drilled a center hole, and made up a makeshift mandrel. Surprisingly, an ordinary carbide tip cut the rubber fairly easily, distorting under the tool much less than I expected.

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I then put the rubber disc in the vice and cut the relief for the frame tube with my hand drill, using the same hole saw I used to fit the metal cross brace to the frame. The result is not a thing of beauty, but I mounted the tank and it fits very well. This is what I have so far:

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I will need to ensure that the rubber stays in place during and after installation of the tank. I briefly considered gluing the rubber to the frame, but that feels iffy, so my current plan is connect the two rubber spacers mechanically. Once I get the second spacer made up for the rear (a slightly more involved shape), I can bolt a threaded rod between the two of them, with some oversized washers on either side of each rubber mount to prevent flexing. This should ensure that they stay aligned to each other and perpendicular to the frame tube, but nothing but rubber contacts the tank.
 

Tanshanomi

Well-Known Member
The Bride's tank mount is (sort of) complete.
I finished fabricating the rubber tank bumper assembly, and mounted it to the frame temporarily with some hose clamps. I then re-mounted the tank, ensured it was aligned properly, and hit the cross-brace with a couple of crappy, spatter-y tack welds with my flux-core welder. It’s not pretty, but it positively locates the tank securely on the frame.

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I have juust enough clearance for the throttle cable, the choke lever, and the petcock. The only thing more difficult than mounting the tank with the carb in place is mounting the carb with the tank in place.
I will eventually have to have this more professionally welded, but for right now, I can move on to mounting the seat and rear fender. I’m really starting to like how this is coming together. As the saying goes, “90% complete, 90% to go.”

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Tanshanomi

Well-Known Member
The Bride’s bodywork is coming along nicely. I now have the fuel tank, muffler, and seat solidly mounted to the bike.

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The seat is one of the many generic, Asian cafe seats on Ebay. I bought it brand-new for less than $30 a few years ago, but ended up not using it for my CL125S restomod project. Fortunately, it works very well here.

I added a post and rubber donut just behind the tank that engages the forked bracket under the nose of the seat. The rubber pad under the center of the seat was just slightly too far back to sit on the frame crossmember, so I had to add an extension. Two outboard rubber pads at the front of the seat have somehow disappeared over the years, and wouldn’t contact the frame anyway. As a result, the only contact points toward the front of the seat are along the center-line, so the plastic seat pan can twist torsionally a bit. It’s not horrible, but I still might feel compelled to do something about it. ...later on.

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At the rear, the sheet metal brackets that came with the seat worked nicely, once I put them in the brake and bent them outwards. Further forward, you can see the rubber block sitting on my makeshift frame extension. Yes, I have proper, matching, 6mm fender washers on order.

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As a side note, note how the bolt on the left does double duty as the muffler bracket mount. You can also see the hose clamps behind the heat shield on the exhaust pipe. I tack-welded a 1/4″ square tube to the shield’s mounting brackets. That spaces it out from the pipe a bit more, which improves the looks of the exhaust dramatically.

With the seat and exhaust in place, I can move on to fitting the rear fender. At the front, there’s an existing fender bracket (visible in the under-seat photo above). Unfortunately, it’s too far forward and some sort of intermediate bracket or extension will be required. I ordered some rubberized P-clips that I may use to attach the fender to the frame loop, or I can also simply use longer bolts for the seat/muffler mounts, so that they will pass through the sides of the fender. I have not worked out taillight selection or placement yet.

I want to match the appearance of the steel front fender and plastic rear fender as closely as I (affordably) can, so I plan to spray-paint the front fender with a semi-gloss white enamel. I also plan on painting the white front wheel and brake housing Kawasaki Gentry Gray, to match the rear wheel. To see how that all might look, I gave the bike a quick virtual makeover in Photoshop:

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Tanshanomi

Well-Known Member
I have the rear fender on The Bride. I managed to get it mounted straight, and I didn’t have to resort to P-clips. Drilling a few holes in plastic may not seem like much of an accomplishment, but it took longer than expected.

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I had to make spacers to fit between the original fender mounting bracket on the frame and the new fender. You can’t really tell from the photo, but the bottom ends had to be cut at a noticeable angle from perpendicular to match the curve of the plastic fender. Opposite, on the inside of the fender, there’s a sheetmetal stiffener.

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I extended the bolts for the seat and exhaust to pass through the fender, and I think that worked well. The bolt on the right is too long because it doesn’t pass through a muffler bracket, as the the one on the left does, but it was the only matching bolt I had. I’ll shorten it at some point.

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I also mounted the tail light and license plate. The no-name LED tail light is attractive and bright enough, but the bracket holds the license plate almost horizontally. I hope I never get hassled about it for what amounts to a scooter/mini-bike hybrid. And yes, that’s a Vermont plate. I haven’t had the gumption to take it to a Missouri inspection station for a VIN verification. My state is super-strict about vehicle titles.
The next item on the punch list is some pins on the swingarm to engage the snail adjusters. This will likely be a pair of M5 socket-head screws, threaded in and then reenforced with a couple of tack welds on the front of the heads. Then I can mount the final drive chain.
I suppose I’m probably pretty close to being able to start ‘er up, if I wanted. Unfortunately, there’s nothing under that plastic pulley cover right now. I know just enough about CVT tuning to know that I know nothing about CVT tuning.
 

Tanshanomi

Well-Known Member
I have no idea what what this NOS side stand originally fit. I don’t even recall under what circumstances it came into my possession.
Even though I could bolt it to the frame, it clearly isn’t going to work like this.

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Taking the most direct tack, I cut it in two with a hacksaw and then chucked each half in the lathe, turning the ends down to fit the ID of a steel tube I had lying around. I enlarged the hole in the frame to 12mm, so I could fit a proper shoulder bolt for the pivot.

Ahh, yes. This will work much better.

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I originally planned to weld it, but I wanted to be able to adjust the length if necessary. I briefly considered threading the ends, but that would complicate orienting the foot properly. So, I simply made both ends an easy press fit, cross-drilled each end, and cut some M6 x 1.25 threads. I probably could have used setscrews for a more attractive look, but I had the button-head hex screws, and with a lock washer under them it's a nice, secure assembly.

Don’t worry, it looks just as ugly in the up position.

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Regardless of how unsightly it is, the bike stands up on its own now, so that’s a win!

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Tanshanomi

Well-Known Member
Since I want the The Bride to be a full-fledged street bike, I am going to equip it with full lighting, including turn signals, a speedo light, and dash indicators. However, these will initially be just battery-powered. I have purchased a high-output alternator, but since the engine ignition is self-contained, I will worry about installing the charging system and making the electric starter functional after I’ve ridden the bike. I first need to convince myself that will be practical enough to be worth that effort.

In the meantime, the wiring will be super simple for a full-size motorcycle, overkill by mini-bike standards.

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Tanshanomi

Well-Known Member
I have to add pegs to the swingarm for the snail adjusters, but I needed to get the wheels in alignment first. It drives me crazy when you can’t trust the accuracy of indexing marks. So, I disassembled my Chop Source frame jig and I’m using the side rails to align the rear wheel to the front. The front tire is right at 1-3/4″ narrower than the rear, so a length of 7/8″ OD tubing on each side take up the space perfectly, keeping the two rails parallel when clamped against the wheels.

I’ll use a pair of 6mm socket head screws as pegs for the stops. They’ll get threaded in, then spot-welded at the front, opposite from where the snail adjuster plate contacts them.

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Tanshanomi

Well-Known Member
I attempted to add stops to the swingarm for the snail adjusters. My plan to use 6mm socket head screws seemed easy enough to implement, and in fact the left side went fine. I marked, drilled, and tapped the hole, and verified that the socket head engaged the scallops on the adjuster properly. All looked good.

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I then did the same thing on the other side. Or at least, started to. With the hole drilled, I was tapping the M6 x 1.0 threads, when—

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Fuuuuuudge. (Only I didn’t say fudge.) I was sooo close!

I spent most of 90 minutes try to get the broken tap out. I tried Vice-Grips, needle-nose pliers on the flutes, tapping it with a chisel, everything I could think of. No joy.

I’ve purchased a tap extractor off Ebay for $21. It should be here in a week.

If that doesn’t work, I will need to go to Plan B. I’ve had these Suzuki adjusters with rear-mounted screws for many years. About a decade ago (literally) I made these support plates to adapt the adjusters to the skinnier ends of the YZ125C swingarm. If I can’t extract the tap, I’ll grind it off flush and spot-weld these plates to the outside of the axle mounting slots. I don’t like this solution as much, mainly because it’s easier to get the wheel adjusted accurately with snail adjusters, but I have a workable solution.

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I can’t stop kicking myself. I was sooo close!
 
The chain adjuster setup is on hold until my tap extractor arrives (which, by the way, several knowledgeable people have assured me has zero percent chance of working for me). So, staying busy in the meantime, I’ve begun fabricating a caliper bracket for The Bride’s rear brake. The caliper is a single-piston unit intended for Suzuki Vinson 500 four-wheelers. The aluminum plate is a random slab of 1/2" mystery alloy that I dug out of the odd scrap bin at my local metal warehouse a long while ago.

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To all those nay-sayers who insisted that Walton Tap Extractors are useless junk, I'd like to go on record as having proved you absolutely, 100%...correct.

I did everything properly: I ground the tap flush with the surface, inserted the fingers all the way through, and made sure that the collar and inner shaft were kept tightly against the piece. Unfortunately, basic physics just doesn’t permit those tiny fingers to transfer the torque necessary to break the tap loose. I guess it’s just another $21 in tuition at Experience University.

Looks like screw adjusters it is!

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To all those nay-sayers who insisted that Walton Tap Extractors are useless junk, I'd like to go on record as having proved you absolutely, 100%...correct.

I did everything properly: I ground the tap flush with the surface, inserted the fingers all the way through, and made sure that the collar and inner shaft were kept tightly against the piece. Unfortunately, basic physics just doesn’t permit those tiny fingers to transfer the torque necessary to break the tap loose. I guess it’s just another $21 in tuition at Experience University.

Looks like screw adjusters it is!

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I’ve had this work and had them not work. Obviously, it all depends on how wedged in there the broken tap is. If it’s been hammered on, etc. , it’s not likely to work. Heating the tap cherry red and letting it cool to anneal is sometimes a good strategy. Sucks in any case! :p
 
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