my new speedway scorpion

I just picked up a speedway scorpion. It looks good but its missing a lot of parts and needs a lot of work. The seat tank and engine are not original and its missing the original clutch, clutch guard, jackshaft , rear wheel spacers, throttle and brake cables one of the brake handles the throttle grip light bulb for the headlight, the tail light, the front brake caliper and the rear brake is missing the armature,. Someone cut a chunk out of the top frame between the seat and tank and replaced it with bar stock for god knows why. the left side front fork shock is stuck bad, I already tried once to free it by hand with penetrating oil and failed. and the right side is freed up but sluggish to respond. and the hardest part to replace would be the plastic sprocket mounting pace, it was cracked to bits and came apart when I loosened the bolts. I'm looking into replacement options. I think the engine is either an h50 h60 or h70 but the model numbers are from sears so they don't say which one. the original engine is an hs40 but I think ill keep the big engine I want the extra power. in order to keep it I'll have to center it better in the frame, its exceedingly right side heavy and partly covers the foot peg on that side. to fix this I think I'm going to mount the sprocket on the jackshaft that lines up with the clutch outside of the frame to allow the engine to be moved over further. I'll try to find a way to level the carb and buy a custom header. for the time being I'm keeping most of the bike the way it is and just focusing on getting it assembled and running and fully functional. I can fix the frame and have a better seat made and find an original tank later. I think I wont bother with the finding an original clutch or cover for it they wouldn't work with my currently planned setup. I cant wait to ride it!

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Well-Known Member
Looks like a h50 with electric start nice!!! I would keep it that way. Gotta get the right tank and wheel spacers. Be sweet runner or keep ya eye out for that clutch cover a d disc brake.
speedway brake.JPG

I need the armature that is missing on this brake and whatever this is supposed to use to secure it to the forks. this assembly looks a lot like the rupp brake assembly's so would a rupp armature fit? also I need the wheel spacers or at least there lengths so I can have some made up.

another part I need is the front brake caliper. I know some sties are now selling mechanical disk brakes for go karts would one of these calipers work on this bike?
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Well-Known Member
To connect the drum brake to the rear swingarm you need a piece of aluminum in the shape of the out line it made on the backing plate. You can kinda of see it. I tell you thou it is a pain getting everything lined up! Its about a inch thick. See if ya pop can whip ya up one. Can i see the hub ya dad made for the front?
sprocet mount..JPG

this is the new rear sprocket mount next to what's left of the old one, I got the new one a bit dirty after holding the old one. my dad can fabricate most of what I need but id prefer not to lean on him to heavily on these projects. he is a busy person so I only ask if its something I know I cant find get or fabricate on my own. this part qualified.
on a different subject dose anyone know how to force out a stuck front shock on this bike without damaging it?
update: the new sprocket mount is installed I works well. and I just pulled the front forks apart to find out why the left was stuck and the right was sluggish. there was rust inside both and a plastic sleeve in the left frozen side had slid past a stop and jammed a pace of itself below it beside the spring, that's why it was stuck. the left side was wallowed out a bit in the center, I'm not sure why but I think that's what let the plastic it past the stop. I've got an idea how to replace the plastic but I'm not sure what to do about the widened middle of the shock.
I also looked at how large the missing wheel spacers will need to be, its a lot smaller than I first thought, less than an inch on both sides. I have some material for the new spacers and I just need to drill them out and cut them to size. the last thing I did was order the missing bearings for the jackshaft. but I still need to order the jackshaft itself.
I was looking at how to fix the problem of how far the engine sticks out to the right. I was going to shift the left side sprocket on the jackshaft to the outside of the left side bearing to allow me to move the engine over but after test fitting a 10 tooth sprocket on that side , I found out it wouldn't fit there without hitting the frame. maybe a 9 or 8 tooth wood fit but if not I may be swapping the engine to a more original less powerful hs50.
I just picked up the model and serial numbers off the engine. its craftsman model 143-606102 serial 0231-06602.. if anyone knows what size engine this is pleas let me know.
Hey you're local to me! I saw that on Craigslist but didn't have the $$$ to go for it. Enjoy.
ill do my best to do right by the bike, undoing as much of the damage and abuse as I can and bring it it back to life as a beautiful, scary fast, rider. It'll be a while before its running but after its running if you show up at any of the local events I could let you take it for a spin.
I got more done on the bike. so far ive taken the forks apart and found out why they were stuck. a pace of the plastic bushing on the right side broke free and lodged itself next to the spring jamming up that side. also that same side is a little wallowed and bent I think it should still work but id replace it if I could. to replace the bushing I took a plastic fork bushing made for a from a rupp and cut it to fit. but I'm not sure yet if the thickness is right. Ill have to see after I clean out the fork legs and re assemble it.

I also installed the new jackshaft. but I still need a small spacer for the outside sprocket. the sprocket on the outside is where I plan on running the chain from the clutch. this will allow me to near perfectly center the h70 in the frame.

the photo below is just a better shot of what one of the previous owners did to this poor bike.

I just got a new tank for the bike.

and this is the first time the tank met the frame. and now that I have the tank the frame is stripped so I can have a shop repair the damage done to the top of the frame. honestly why do people do stuff like this to bikes?

I now need to decide on how to hook up a throttle to the engine which is missing all the linkage and the throttle plate. and I need a carb wedge to level the carb but if I have to spend money on it I might just swap the carb for a bigger mikuni for better performance. its still up in the air on that.
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sorry it took so long to have an update, the welder finally got around to working on my frame but he did an excellent job. the frame looks like new and my reproduction seat cover just arrived. ill get some pictures next week. now I need to get some seat foam to fill the seat cover. (it didn't come with any).

this is a good step forward but I still have a lot to do.
speedway mini bike frame  repair  003.JPG

this is the section the welder replaced he did a grate job.

speedway mini bike how it looks now 004.JPG

this is what the frame now looks like. the little metal pace over the jackshaft slot is there to allow me to mount the engine more evenly in the frame. the chain is going to run outside the frame rails instead of inside.

speedway mini bike partly  mocked up.JPG

this is the frame partly mocked up with the tank and seat cover. I still need foam to fill the seat cover.
I like the seat cover. Where did you get it? I will be needing a tank to for my speedway scarab.

What are your thoughts on those plastic bearings in the neck? I was thinking about replacing those with actual ball bearings.
I like the seat cover. Where did you get it? I will be needing a tank to for my speedway scarab.

What are your thoughts on those plastic bearings in the neck? I was thinking about replacing those with actual ball bearings.
I bought it on ebay from a seller named holokidd he doesn't currently have any listed but he should be able to make more. as far as the plastic neck bushings I would only change that setup if there was a problem. if it aint broken don't fix it.
I finally got some more work done on this project. I just bought a house (fixer upper) so priority's changed and I don't have as much time or money to work on this as I used to . the frame modifications and painting are complete the tank still needs a good paint job but its to cold for that right now. I assembled the bike and added the control cables and the chain to the rear sprocket. I haven't hooked anything to the engine yet because it needs modifications to become the scary monster power plant I want it to be. hears a picture of it in its current state, pleas note in the picture the engine isn't bolted in, it normally sits a little further back. and the frame has gotten a little dusty from sitting in my basement. I also included A picture of a new project I just picked up, an mtd trail flight mini bike and its got 90% of the original parts including the original hs40 with lighting coil headlight and light switch. the engine has no shroud but I have a later model hs50 shroud that seems to fit nicely that will work until I find a good deal on the correct shroud. the bearings shocks and brakes all work the engine still turns, the tires hold air, and I just serviced the clutches. so I should have this running as soon as the weather warms enough to properly tune the engine. mtd before shroud side.JPG speedway frame complete.JPG