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


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Back up on 'er wheels. Reassembly of The Bride is progressing, slowly but carefully, with plenty of grease and threadlocker this time. It’s off the lift, hopefully not to go back on it anytime soon. This is the first time I’ve had both wheels mounted since being painted to match; the improvement in looks can hardly be overstated.



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I took some friends’ advice and added a little Swiss cheese to my engine mounts. It was a heck of a lot of work to save less than half a pound. Beyond about a 1/4″ deep, hole saws can’t clear the swarf very well and get rather fussy. My nifty aluminum-cutting router bit made quick work of beveling the edges, though. I still might add some holes down the center of the base plate. It’s not quite as thick, and a couple of holes might help keep crud from nesting in the channel under the engine.

I’m still undecided about a finish. I don’t really want to spend the time to polish the surfaces. I could just give it a brushed finish, but paint might look better, longer. I’ve thought about either gloss black, satin black, but I have some leftover Gentry Gray wheel paint; painting it to match the wheels might look really good.



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Sorry, @Minimichael; I went with the Kawasaki Gentry Gray wheel paint for the engine mounts, and I’m happy with my choice.


Final assembly is when you discover how many things you’d previously deferred, and then forgot about — such as figuring out how/where to tether the middle of the rear brake line. Fortunately, I was able to drill and tap the engine mounting plate for some P-clips without marring the paint too badly.


Springtime landscaping and lawn seeding has usurped most of my workshop time lately, but I’m managing to make a little progress here and there. I got the engine into the frame this morning, which feels like a minor accomplishment.



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When I went to reinstall The Bride’s rear turn signals, I noticed that one of them had a slightly deformed lens. I chalked it up to heat from the bulb combined with cheap-o design and construction. Since two of the lights were inop anyway, I switched to another equally cheap-o set from my cabinet of unused electrical junk. As I was installing the exhaust, a light bulb went on. Ohhhh.

So now I need to devise a different location for mounting the turn signals.

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After I posted my issue with the melting turn signal, an online pundit suggested I relocate the muffler, rather than move the rear turn signals. I had no intention of totally re-fabricating the exhaust, however, there is a bit of extra clearance in the exhaust flange mounting holes which allows some slop in positioning the pipe. When I reinstalled the exhaust pipe, I shifted the pipe out away from the bike as far as possible as I torqued down the exhaust nuts on the head studs. This bought me a small but significant amount of extra room between the muffler and the turn signal.


Now, all I needed to make was a new mounting bracket. Exhaust Bracket 2.0 is made from 3/16th inch steel. Frankly, it’s much more attractive than the original 1/4″ alloy one, which had two mushy bends and just looked kludgy. This one has a much cleaner bend, done in the shop press. It’s certainly stout. Cue the phrase, “that ain’t goin’ anywhere.”



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I’m designing a battery box for The Bride, using both permutations of “CAD” — cardboard and computer. First, I figured out what I needed with some old scraps of illustration board.


Once I had something that worked, I measured the dimensions. After I transferred that into the computer, I printed off a full-scale template on stiff paper to ensure that I hadn’t screwed up the dimensions. The sloping shape will allow the box to snake into position within the frame tubes with the engine and swingarm in place.


And finally, I added a bunch of drill holes along the crease lines and at the intersections of cuts.


I discovered this trick while making the battery box for my CL125S. Drilling out the hole locations first, before any cutting or bending, ensures that I lay out the dimensions accurately — just connect the dots. Then, once it’s in the bending brake, the reduced mass along the bend line encourages the metal to fold in line with the holes. The blue line is where I’ll add a rolled stiffening crease with my die roller. (Die rolling straight across a piece, edge-to-edge, keeps away the “oil can” distortion pixies.)

I’ll pick up an 18 gauge sheet of mild steel after work tonight and see how it goes.


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I successfully cut my battery box pattern out of 16 gauge steel I got from Lowe’s.


This is the point when things went amiss. You know that theory that rolled metal has a “grain,” based on the direction it was rolled? If not, here’s an illustration I found online:


Well, I thought it was just that — theoretical; certainly true, but the sort of thing that only aerospace engineers and production machinists needed to concern themselves with in practice. Well, I got a practical lesson when I attempted to bend my flat shape into a box, using my tiny Harbor Freight bending brake.

I bent the bottom floor pieces into place just fine, but when I moved to the vertical angles, three in a row cracked at about 50-60 degrees of bend. You can see from my bends in the other direction that I wasn’t trying to make super-tight-radius corners. (You can also see where I mis-drilled one of the perforation holes slightly. I have shamed myself.)


In the other direction, however, the vertical bends simply folded and cracked rather than smoothly bending. In this photo, I’ve already ground one side of the break smooth in preparation for welding, but it shows how sharply it folded before starting to crack.


A good dose of heat probably could have prevented this, but it didn’t occur to me because I’ve never had this issue before. In any case, a bit of crappy flux-core welding [that I am NOT going to show you] and I was back in business.

Unfortunately, all this is effort is most likely for naught. Looking where the finished box and battery could be located within the frame, I came to the realization that it just doesn’t fit. Not only is the battery way too close to the heat of the cylinder head, but the support brace on the Yamaha Monocross swingarm doesn’t have enough clearance. It’s tough to visualize based on this photo, but there’s only about 1-1/4″ between the bottom rear corner of the battery box and the vertical swingarm tube. I don’t want to hit a big bump and discover that the swingarm hits the battery box. I thought I could get away with it because the closest point of interference is pretty near the swingarm pivot, and the rear suspension only has about 4-1/2″ of travel at the rear wheel. Ultimately though, I had to admit it’s just too close to comfort.


Going forward, I have a couple of options. I could move the battery to another location. There’s an equally tight spot between the back of the engine and the swingarm pivot, but proximity to the cylinder cooling fins would still be a concern. Alternatively, I do have another, physically smaller AGM battery on hand. It would be much easier to mount, but it’s an off-brand, 3 AH battery intended for my kickstart-only Bultaco 360 roadster. It’s rated at only 50 CCA, too small to reliably spin The Bride’s electric starter. I chose the existing battery — a Motobatt MB5.5U rated at 90 CCA — because it was as small as I dared go.

So, I now need to do what I always do at these junctures: go down to the workshop, pull up a stool, stare at the bike for a while, and think.


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Best option I see is to make/mold a tray under the seat to lay a battery in on its side. Looks like you’ll have to clearance the fender (cut a big hole in it).


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I did some practical tests, and my cheapie 50 CCA battery [Weize YTX4L-BS] is able to spin The Bride’s starter motor at a similar perceptible speed as the larger 90 CCA Motobatt. This battery is standard equipment on many small bikes equipped with electric starters, including the Kawasaki Z125, Yamaha TTR125LE, and a whole slew of 50–90cc ATVs and scooters, so I’m going to assume it’s up to the task of starting a GX clone engine.

I put the torque converter housing on the engine and found that the little guy will nestle quite nicely between the motor and swingarm. So, I have a path forward and a new battery tray is in the works.


As for the Motobatt, I don't plan on using a battery as large that for Bultakenstein (my current Bultaco roadster project), but perhaps I can keep it charged and in good shape until I get around to a project with an electric starter. I have a single cylinder Ducati-engined Aermacchi lined up for the long-term that it'd be ideal for.

...But then, that's not really a minibike discussion, izzit?



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I tried modifying my earlier steel battery box to fit my new, smaller battery. It turns out that not only can I not weld, I also cannot measure. The result was still larger than needed, and too big to fit the space available behind the engine.


To be fair, I didn’t want to shrink the size too much, because I knew I needed to leave room for some sort of cushion lining to prevent the steel edges from gouging the plastic battery housing.

I have a hot-air plastic welding gun and I keep a pretty good stock of HDPE (high density polyethylene) plastic on hand. I’d already had the idea of making non-conducting mounts when it occurred to me that I could simply make the whole box out of plastic sheet. There’d be no need to line it, and plastic is so much easier to fabricate than steel. I dug out a big scrap sheet of HDPE that had been a pistol target backer in a previous life, but still had some unperforated sections that I could use.


If you’ve never used a plastic welder, it’s a pretty slick process. They’re not very expensive and it’s not hard to learn; you just need a bit of practice to learn the proper temperature and speed. And always make sure you’re using the correct filler rod.


Like so many things, success mostly comes down to decent prep and proper jigging.


Once I had a box, the next step was mounting it.


The battery box mounts to the bike in three places. In the image below, you can see two of them. A steel angle support bolts through an existing hole in the frame right below the swingarm pivot on the right, and the inboard rear corner is supported by a post that clamps to the lower frame tube.


The third mount is at the right front, where an angle bracket mounts to the same bolt as the rear brake line guide.


I’m using countersunk allen screws that are flush with the tray floor.


It might get too much engine heat as it is now. After getting everything mounted, I realized that battery could be moved slightly lower and more rearward. The current location was determined solely because of the position of the existing hole in the frame.


I still need to make some sort of door or strap, but a bit of painter’s tape will suffice for now. I’ve got a solidly mounted battery, so I can get on with making up a wiring harness and configuring the electrical equipment.


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Very nice work. And really good demonstrative pics and commentary. I've thoroughly enjoyed watching you design this thing. Thanks for taking the time and letting us read along with all your thinking and decision making. I like the countersunk fasteners because they're doing double duty... By holding, and staying out of the way. And I always imagine plastic welding must be messy. But yours is looking so clean and finished. Now, is that plastic weld going to hold?
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I always imagine plastic welding must be messy. But yours is looking so clean and finished.
Mine looks pretty crappy compared to others I've seen, especially with harder, higher temp plastics than HDPE. As I said, it's just like welding metal; once you get a feel for temperature and travel speed, it's fun.

Now, is that plastic weld going to hold?
With proper beveling and filler application, a single corner joint can be effectively as strong as the rest of the structure. Once you make a triangulated box like this one, it's really strong. I didn't add any fillets on the inside corners, and you could still heave this tray against a brick wall as hard as you wanted and probably not do much beyond scratch it up a bit.


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The die-cut vinyl “Panther” decals I originally intended to use turned out to be prohibitively expensive to make. The setup fees print shops (both local and online) charge make “onesie-twosie” custom cuts rather impractical. So, I integrated my Pather logo into a design to fit a standard round decal. offers this cool brushed-alloy-look background. Eleven of these 4-inch round decals cost me $30. Interestingly, when I actually got the package, it contained 14 stickers. Bonus score! With a dozen extras, I don’t need to worry how durable or fade-resistant these are.

Four inches in diameter is fairly large, but they’ll be hard to miss. The whole purpose of these decals is to squelch questions at the inspection station about what the hell this thing is, and why the registration lists “PANT” as the vehicle make.



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If it seems as though I spent an inordinate amount of time on the battery tray, you’d be correct. But — to steal a saying from Home Built By Jeff“anything worth doing is worth doing twice.” I re-did all the brackets to move the battery down and back, so it would sit slightly farther away from the engine.

I shortened the angle bracket and raised the hole at the rear, where it bolts to the frame.


I finished the plastic pillar/clamp support at the inside rear of the box. This was complicated by my unwillingness to spend one more damn cent on hardware. (The cost of new fasteners has been one of the unexpectedly painful parts of this project.) It’s not pretty, but it holds the battery tray solidly and didn’t require any frame mods.


And finally, a new front bracket, hiding behind the brake line P-clamp. Looking closely, you can see the ample space between the top front corner and the spark plug lead. With my initial setup the battery was barely kissing the base of the plug lead where it exits the blower housing. Yeah, this was worth the re-work.


The big velcro strap is a suitable retainer for now. The battery is pretty snug in there, but I might need to add a strap that goes over the top of the battery as well.