HARO SR20 BMX/EH035 Robin Subaru - Home Build

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policetac

New Member
Hello. Well, to those who haven't seen my "welcome" post, I'm Rick.
(I used to sell tactical equipment hence the username.)

I'm an older guy, retired, with a tinkerer's soul. My latest doldrums destroyer is going to be a project where I take the engine off of my stand up scooter, and mount it to a 20" HARO BMX bicycle.


There are a couple of reasons for this build.

One is because of the ways the laws are set up in my region, (which I will highlight during the build)
And the other is because I always wanted to design a cool gas powered BMX bike.

The bicycle chosen is a 20" HARO SR20 DVS DX Aluminum BMX bike. The DX Engineering High-Strength Aluminum Tubing is extremely light yet amazingly strong. It's originally designed and used for making very high quality radio transmitter antenna's. I took a few pictures of the bike. I've included pictures of the wheel gear sprocket setup that I've already designed.

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The engine is coming off of my Martin Monster stand up scooter.
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It is a working scooter that I actually ride all the time. (I live on the beach so I get plenty of opportunities.) Because of this, I want to make sure this build is designed to allow for a "quick swap" of the engine from the scooter to the bike and back again.

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The engine comes off tomorrow for fitting. I'll post more then. Goodnight!
 
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I have seen elsewhere a complete minimoto motor, connecting frame, and back wheel mounted over a back wheel to drive as a whacking big drive roller.

Could you make a sub assembly that fixes with one or two bolts for quick transfer between uses?
 
First off, I'd like to say hello to all who took a few moments to check out my thread.

Hello! :)

Yea..., I got a little bad news the other night. I had finished my power sprocket so it was ready to go. My wheel sprocket setup was finished and the design was working perfectly. I had an old chain all reconditioned and ready for sizing. (It was running the gears as smooth as silk.) And I had my scooter all ready for the motor to come off. (I had done it before so I knew that wasn't going to be a problem. Checklist complete!

Ready for "Mock-up!"

UUuuuuurrrrcccchhh! STOP! Whaaa???

I just got the engine off. Set it down. And proceeded to take off the power sprocket.
I had to do this because I had decided to configure the swap to use bicycle chain and the appropriate gearing for safety reasons as the teeth are a lot deeper and would therefore minimize chain slippage.

So anyway, I take off the sprocket and go to fit the new one. WRONG! (Measure twice, cut once my grandfather used to always say...) I ordered the wrong sprocket. I eyeballed (from a picture - shakes head) the diameter for the drive shaft. Needless to say, I think I need better glasses because I was off by a good 3 or 4 millimeters. (Might as well have been five inches for what it's worth.) Oh, and since I had already ground the teeth for fitting, returning it is no longer possible. (First delay- order new sprocket)

Okay.., well I'll pick up the motor and hold it in place and see how well it's all going to line up anyway... Not very well. I soon realized that the mock up I had in my head wasn't going to work quite as well as I thought. The gearing is going to be a whole lot closer to the frame than I had for some reason imagined. So much in fact that a whole new set of ideas on how to mount the motor were going to be needed.
(Gonna need a welder!)

So, unfortunately just as I thought I was ready to slap this thing together lickety-split, everything is on hold for a bit until I can weld a couple of mounting brackets on to the frame of the bike.

Needless to say, I'm kinda at a stand still for the moment. Hopefully I can get a buddy of mine to stay home for the weekend one of these weeks so I can convince him to let me use his welder for a few hours. (Easier said than done. The weather where I live has been great and he's got a new boat he likes to take out these days!) lol

So anyway..., It's going to be a few before I can get back to this thread and update it with some progress. Hopefully not too long though.

Until them..... :)
 
Yea, I just realized that I sheared my clutch bell as well. New part doesn't come in until the first.

But, I've got some ideas on how I'm going to do the frame mounts at least.

OH! I also had a brilliant idea if anyone wants to tell me the feasibility of it...
Here it is. The idea is to add a couple additional rear sprockets incrementally larger in size and separated slightly with spacers. Then using a de-railer set that functions properly, adjusting it to be able to change gears as I ride.

Waddayathink???
 
i don't think he's referring to a jack shaft, i think he means using multiple rear sprockets together (not the bikes cassette). and then using a second de-railer on that side.
yes?
 
Yes. I would not be running the cassette, but rather a couple of them situated correctly so that a standard cable derailleur will shift them rather easily..shft.
 
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Well, I ordered the clutch housing today. I can't believe I couldn't find that little brass or pot metal dish on the back side there all by itself. That's all I needed but I could not find that individual part for anything.

Heck! I couldn't even figure out it's name!!!

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And yea.....

I kinda figured that out a little bit ago... LOL

What? Oh! That it's a common part and all over out there.. (I never did the measurements or really looked.) I just figured I'd look for it specifically. lol

Clutch Drum!
 
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