New member Fox Frankenstein

Well, it's been a number of days. Took a bit longer than I expected. The wiring is done and the carb bracket has been fixed. Carb bracket was just a matter of getting the old studs out, then drilling it for machine screws to reattach the carb. Simple fix. The big one was the wiring. I ended up mounting the battery box to the bottom of the seat. You can see in the pictures below it just hugs in there between the frame tubes. The last pic was testing the wiring before beginning wrapping the main run from front to back.

Finally, I got around to taking a short video showing the final lights working and firing it up. As noted in the video, I have to finish wrapping the wires up in electrical tape and clean up the wiring in the headlight, but it's all there and working. Also, apologies for the fingers, I rarely take videos with my phone.

The carb just needs some final adjustments when you give it the gas as it seems to bog down a bit. But that's just a matter of riding it and adjusting as I go.
Heya all, It's been a while since I updated this. Not much happened with the bike last month as I blew my money on a 3/4 helmet and OTG goggles. Really the only other thing that happened was a NOS Fox sissy bar was tracked down for it and put on at the end of February. Bar had a crack in it but the guy it was bought from is a professional welder and he happily filled the crack and cleaned the location it was filled.

That brings me to this month and the new stuff that came in. That cheesy $3 control hub had something break inside and no longer reliably turns on the left signal. It's being replaced with a higher quality one that uses mechanical push switches with a really nice feedback on the click for the lights and signals. I picked up a Mikuni clone carb (it still has the Mikuni stampings for some reason, possibly a licensed 3rd party manufacture?). I got a kit of jets for the carb too since I have no idea how the Tecumseh is going to react to this.

I grabbed a speedo setup that tracks speed, tach from the coil pulse, it does other things like tracking signals/lights/hi beams/gas gauge/trip/odometer and other things that I don't care about. Speedo tracks speed by putting in the tire circumference and reading magnets placed on the hub, so that's gonna be a job for gorilla glue I'm thinking. It's really meant to be used on a full on motorcycle but shouldn't have a problem working on a minibike.

You'll have to excuse my fat head in some of the pics. My phone has gone on the fritz and I took the pics with my computer camera. I'll do my best to document things as I go forward with these.

Sissy Bar.jpg WIN_20230301_17_41_49_Pro.jpg WIN_20230301_17_42_10_Pro.jpg WIN_20230301_17_42_39_Pro.jpg
Haven't had much time to really work on the bike. I did, however, get the new carb on it. The connection at the adapter fits perfectly with #10 bolts so a couple of those with nylock nuts got that on the original intake pipe. I like this because it let me use the adapter to get the carb as close to perfectly flat as possible with a level. Hook up the new throttle cable because the old one was a hack-job to make it work with the old throttle assembly and it's done.

The gas tank is currently off because I have to fix a pinhole leak between the tank and where the bolts thread into the bottom of the tank. Also because the area is just easier to work in with the tank off.

Today saw some gas tank work after some running about to get my phone fixed. Hopefully this will resolve the gas tank issue. I started with a multitool and sander attachment to clean off the paint and rust, as well as clean up some of this...interesting...brazing job that is likely causing the leak. Doing this I found out what the rough patch on the side opposite the petcock is, appears to be a tacky bondo job with air bubbles in it. After smoothing out the brazing and bondo somewhat it was time to apply the hopeful fix. To do this, I stuffed some 1/4-20's into the bolt locations and used 2 part cold weld JB weld that is gas resistant. Applying around 3/32" of this to blend the bottom and seal the brazing locations I will then have to hand sand it smooth and finish the blending after it sets fully. Seems like that is going to be a Monday project when it's raining.

Tank Bottom start.jpg Tank Bottom Mid.jpg Tank Bottom End.jpg
Gotta do whatcha gotta do, right? Just noting also that I've had great success with that internal POR-15 tank sealer.
Yea, this is a fix it apparently was going to need anyway to smooth out the bottom of the tank a bit. But back at the shop before coming down the tank spent a week with rust remover in it and getting a shake down with nuts a couple times a day before a coat of tank sealer was put in. Once back at the shop in a month or so it will get another coat or two of tank sealer.

Either way, this is about the best that can be done for the moment without having the ability to completely strip the brazing and redoing it properly as all the tools to do that are sitting a few states away.

Gotta say, when I started on this thing I didn't expect the level of mission creep that I've been allowing to get in.
Got the new carb actually running on the bike and took it for a ride today. The bike seems to breathe much better than it did on the cheapo carb as well as reacts MUCH better/faster while riding. There is also a definite improvement in overall performance of the engine. Anyway, I made a video for your viewing pleasure.

Well, it's been a good month-ish since my last update. Anyway, the hectic process of packing and heading back to a place with a shop is done and that means I can actually do things. Like tear apart this HM80 with the tools to do so. And sand blast things for painting. Anyway, today I tore down the HM80 to get an idea of what is going on inside. Pictures attached. Overall it looks really good inside, but I'll let you guys be the judge of that.

The case is currently getting prepped for blasting and painting. Now that I have sizing for the valves and springs I can hunt down some stiffer springs, keepers and locks and do away with that goofy stamped keeper. The head gasket is going to be changed out using a thin metal sheet cut into the same shape and permatex to seal it up to give a bit of a compression boost. I'll stay mum about other modifications I'm doing to it. Eventually it will end up with a billet flywheel, just a matter of time.

Tomorrow, hunt down parts. Tag and pull out the electrical to do the updated wiring as time permits. Get the frame, wheels, brackets and whatnot ready for blasting.

Anyway, in other news unrelated to this bike build, Harbor Freight has predator 212's on sale for $99 and I picked one up. That will end up on a trike I'm going to build for my Wife. Simple stage 1 kit, billet rod, a mild cam, upgraded valve springs/keepers and locks, and aluminum flywheel is all that will end up getting along with the low oil and governor delete. When I get around to that build I'll make a thread for it if there is interest.

Completely unrelated to any of that, I nabbed a generator with a B&S built GN-190 I thought would be a simple carb cleaning and have a running generator. Found out the damned engine had been submerged in saltwater at some point. I have that engine completely torn apart and will someday get around to buying new gaskets, piston rings, valve train kit since the intake was seized open, carburetor. I sort of wonder if it shares parts with the intek 190's, I haven't found any definitive answers to that yet.

Bore 1.jpg Bore 2.jpg Camshaft.jpg Conn ROd Journal.jpg Conn Rod Wrist.jpg Crank Journal.jpg Head Cover.jpg Piston.jpg Sump.jpg Valve Springs.jpg Valves.jpg Wrist Pin.jpg
Saturday morning and I got Wimbledon White paint on order for the engine, various other paints as well. Also got side cover gasket, breather gaskets, breather filter, oil seals, NOS piston rings, new stock valve springs, a washer missing from the head, and a replacement bolt for the flywheel baffle since the old one snapped off on one. I'll revisit the valve train at a later date when I move on to a billet rod/flywheel. With 5/16" valve stems I almost have to source out automotive parts from something like a 4 banger it seems.

Anyway, for the head gasket I want to remake with thin sheet metal and permatex seal, I'm open to suggestions on what metal to use. I'm currently internally debating between copper or aluminum but suggestions from others is appreciated.
Today I sat down with my electrical components and torn down harness that kept blowing fuses (the original cheapo control switch for the turn signals had a short in it) and redid my wiring diagram. I laid out all my pin outs along with it. Some interesting additions are adding a timer to the brake relay which will turn off the brake light after a set amount of time that is adjustable. Putting on a 3 pole switch with a resistor to be able to toggle between a hi/lo mode on the headlight (I have a couple resistors to test how low to take down the brightness). Finally, adding in the alternator to the setup so the battery is no longer in a total loss system. I'm hoping to have it up and running before the Buick nationals come mid-may.

Paints/clear coat and a .020" aluminum plate show up tomorrow so hopefully everything can be blasted, metal prepped, and prime coated by end of the weekend. With the .020 aluminum plate I'll be making a head gasket and seal it up with permatex like a nailhead engine. All the previously mentioned parts are on the way for the engine. Also getting 1/16" thick rubber washers and 10'-0"x1" wide strip, not really for vibrations so much as paint protection at bracket and engine mounting locations.

We'll see how things are progressing on the bike but I should be getting and clearancing/installing an ARC rod in a couple weeks. I'm still hunting down aftermarket springs, retainers and locks but I'm getting closer to finding what I want.

Wiring Diagram.jpg
Well, last week got away from me. Among side projects an entire day was spent travelling to get parts. Along the way a new an opportunity presented itself that couldn't be easily passed up. Specifically a 5hp Briggs that needs a bit of love. When I picked it up it ran with weak compression and spark...and a sticky intake valve. Anyway, this was added to the project list and is set to be the main running engine on my bike. It's currently torn down, block blasted and awaiting 18 lb springs, ARC rod and flywheel after the block is painted, new oil seals, gaskets and piston rings are on the way as well. Currently devising an intake setup for it to accept a slide carb. I'll probably have to do some finagling on the exhaust too since my current exhaust is setup for the HM80. And as far as deck height between these two goes, they're almost identical so I'm not really saving anything there.

Aside from that, I got a growing pile of blasted parts for the parts cleaner. The rusty chrome bits, after a blast, are starting long sultry hydrochloric acid soaks. The gas tank is going to start getting a couple more layers of tank seal in it before sanding the JB on the bottom and prepping it for painting. All the fun stuff running full tilt towards rejiggering the final product.

Oh yea, the predator I ordered is currently stuck in North Carolina with Fedex changing the delivery date to "No scheduled delivery date available at this time". Because of the storms I'm going to assume the facility it made it to is dealing with flood waters. I get this merry image of it floating about a flooded distribution center with a little sail sticking out the top.

Briggs & Tec postblast.jpg

23-04-20 Overall.jpg 23-04-20 Numbers.jpg Briggs Intake Valve.jpg Briggs & Tec postblast.jpg Trailing arm brake delete.jpg
Update, pictures of things blasted. Engine blocks got a long soapy bath and now sport blue stuff covering their naughty no-paint parts. Shocks came in, for some reason I didn't take a picture of them. Oh well, they're black and have springs. The mental image will have to do till the bike is being shoved back together. The lacquer thinner is getting to me. I'm gonna go take a shower and argue with the goblins in my peripheral vision.

Blasted Parts.jpg Frame Blasted.jpg Engines Taped.jpg
More pics of progress made. Gasket for the Briggs and Tecumseh made. Snapped a pic of the shocks I got. I'll be making brackets for them to connect to on the swing arm separate from the typical connection at the axle. This should give some extra height to the bike as well as just make life easier when doing anything requiring the rear wheel coming off. Finally, blasted the Tecumseh flywheel after separating it from its constituent parts. Guess I'll keep the ring gear around in case I ever want to put electric start on the HM80.

The gaskets are cut out of .020 aluminum sheet. I traced the OEM gasket with a wide tip sharpie. Drilled the holes for the bolt locations, then drilled holes in the middle area to ease cutting it out. Cut out the rough shape inner and outer and bolted the rough shape to the OEM gasket. I then spent an hour plus with a pair of fine files, 1 round and 1 half round/flat side, to file it down to the final shape matching the OEM gasket. These will then be sandwiched between permatex on the head and cover to effectively create a roughly 0.023 gasket. Significantly thinner than the 0.085 of the Tec and 0.067 of the Briggs OEM gaskets. both valves for the Briggs now so it's getting brand new intake and exhaust valves. The old ones are hot garbage that's about to self-immolate. Guess I'll take pics of the old and new ones side by side and edit this post with that pic later tonight.

Briggs Gasket.jpg Tec Gasket.jpg Shocks.jpg Flywheel Blasted.jpg Briggs Valves.jpg
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I present to you a tale of 4 brackets told in 1 part. With the new shocks and their 12mm connections putting them back to the rear axle like the original ones doesn't work well. Or really at all. So todays main project was building brackets for the swing arm for them to attach to. The first step in this mad process was to make a pattern I liked. Sometimes it's nice to make a pattern on the computer. Other times a straight edge ruler, protractor and bow compass is preferred, especially when making less intricate parts like these. In this case, of the 4 or so designs I came up with the one on the right was the final winner.

Brackets Pattern.jpg

With the winner selected a chunk of plate was then selected and blasted clean to put the patterns on. The center of the hole was also marked at this time with the spring punch shown in the image below for later drilling. You can sort of make out the dimples it left in the plate.

Sheet Patterns.jpg

With the slightly fun part completed the really fun part could commence. Cutting out the brackets from the plate. Really, the best way to go about this is not with a band saw or sawzall, rather harsh items to attempt to use for that purpose. A cutting torch certainly works but why waste the gas when you have a plasma cutter? So they were cut out and I even stopped tripping fuses when I plugged it into the wall socket instead of a power strip.

Brackets cut out.jpg

With that fun aside I drilled the holes. Not much to that process, just a drill press and stepping up the bit size to achieve the final drilled hole size.

Brackets Drilled.jpg

After all the fun drilling it was a matter of time doing the boring part of grinding them down to their final shape on the grinding wheel. I should have cut them closer as it took literal hours. After grinding, then the filing to clean up all the edges. Then a final media blast to clean the mess I made and we get the final product ready to be welded to the swing arm.

Final Brackets.jpg

There will be some final dry fitting to do to ensure clearances around the rear brake and sprocket as well as some final shaping before welding but overall they turned out quite nice. 9/10, would not desire torturing myself with grinding them from a rough shape again.

Finally, just because it's a really cool piece of old military hardware. The blasting cabinet in the shop below. Full recirculation system is in the works so the cyclone filter doesn't have to be constantly emptied. The mini bike frame fit inside it with plenty of room to turn it around and stand it on end even for some of the blasting I was doing on that.

Blasting Cabinet.jpg