CRF50 engine for custom "moped"?

[Wilco]

Anyone done this? I know there is the "Motoped" but I'm going to weld up a custom frame similar to the coast cycles "buzz saw" (made for electric motors) but throw a modded crf50 engine into it for long distance rides.

Anyone had luck registering it with the DMV? I registered an electric moped with DMV but I had a title for it, not sure how to get a title for a total custom build....

Side note, how is it the electric moped folks get away with street legal bikes that do 60 mph and a gas engine is limited to 50 ccs?

 

[auntiebling]

Special construction is what you're after

 

[Frame Maker]

Sounds like a fun project. Do you have any photos and images of your design?

As for DMV issues, I can walk you through the process when the time comes. Its pretty simple. The one thing to keep in mind as you're building your bike is to keep all the receipts that you use for major components and materials used to build major components. Think of it this way: DMV wants to see the receipts to establish a tax value. CHP will want to see receipts to verify that you haven't used any stolen components in your construction. In addition to a CHP inspection and DMV paperwork, you will also need to get a "brake and lamp inspection". There are a few steps, but the overall process is pretty easy.

Anyway, looking forward to following your build.

 

[Frame Maker]

I just checked out the "Buzzraw". Something like that with a CRF50 would be a blast! I just hope you design a nicer seat than they did. And do you plan to use a girder fork? That can be a fun project in itself.

 

[Wilco]

Yes, that's the bike I sort of want to copy. I had to re-register my old sl175 and was told to get a brake and lamp inspection. The guys at the inspection station gave me funny looks. When I actually went to the DMV the clerk said they didn't actually need that. They just did a visual inspection of the bike and signed off on it. Of course they got one of the digits of the VIN wrong and I didn't notice until I go the new pink slip...

I like the idea of a flat long seat to change riding position or have a passenger. One thing I was going to do was make the seat height adjustable like on a bicycle so that if you do lose engine power you can set the seat right for pedal power. I want to keep the whole thing light enough to pedal if need be.

I'm tempted to just grab a buzz saw frame and try to mod that, but every time i think of spending the $1200 I think for that much I can buy a mini machine lathe and use my friends tig welder....

So this is going to be a loooong process. And I'm not quite ready to give up my KTM 525 to fund it just yet. I also need to learn how to tig weld (done some stick welding already)

I also like the idea of fillet brazing like old bike frames, but I don't have a torch setup.

I don't think I would do a linkage fork, but I might depending on weight savings. Again, the idea is lightweight, enough travel to be comfy, and something you can throw into the back of your suv or hatchback or rack to a bike rack.

I'll post updates, but they may be rather slow. I've got a toddler at home and I'm still working full time at my "day job"

 

[GPzPop]

for the sake of build efficiency, teach your toddler to TIG weld... what could go wrong?

 

[Wilco]

Currently going down the rabbit hole of suspension design... yikes.

I'm finding a fair amount of info on sportbike suspension design and tuning, not as much for dirt-bike. Because I am doing a design that utilizies pedals I am reading a lot about mountain bike suspension systems.

That Buzzraw frameset actually has the bottom bracket attached to the swingarm, which I can't imagine would be pleasant for trail riding. So the idea of using that frame is out.

There are a number of these electric moped designs that all use the same single pivot design with the shock mounts high up in the frame like the buzzraw, the super 73, Onyx, and some other knock offs. I'm not sure why at this point, but I don't think that design will give enough travel on the rear. I'm gonna go for around 6" of travel in the rear.

Also all these designs are for a power source that is generated in the rear hub itself and im sure that changes anti-sag and rise characteristics …

I am going to look up some downhill mountain bike linkage setups to play with. I kind of like the idea of using a higher pivot above the crank with a chain idler to control chain length. Something like ...

I'll need to learn how to add images... sorry

 

[Frame Maker]

Currently going down the rabbit hole of suspension design... yikes.

I'm finding a fair amount of info on sportbike suspension design and tuning, not as much for dirt-bike. Because I am doing a design that utilizies pedals I am reading a lot about mountain bike suspension systems.

That Buzzraw frameset actually has the bottom bracket attached to the swingarm, which I can't imagine would be pleasant for trail riding. So the idea of using that frame is out.

There are a number of these electric moped designs that all use the same single pivot design with the shock mounts high up in the frame like the buzzraw, the super 73, Onyx, and some other knock offs. I'm not sure why at this point, but I don't think that design will give enough travel on the rear. I'm gonna go for around 6" of travel in the rear.

Also all these designs are for a power source that is generated in the rear hub itself and im sure that changes anti-sag and rise characteristics …

I am going to look up some downhill mountain bike linkage setups to play with. I kind of like the idea of using a higher pivot above the crank with a chain idler to control chain length. Something like ...

I'll need to learn how to add images... sorry

Looking at the pictures of the Buzzraw, it looks like the bottom bracket is attached to the swingarm right at the pivot. So I think any adverse affects would be negligible and you'd benefit from simplicity in keeping even tension (slack) on the chain.

Personally, I'm curious why you'd want to utilize pedals with a CRF50 engine? My understanding is that with ebikes they can be programed to provide "pedal assisted" power to extend the range. With an ICE power source, range usually isn't an issue. So pedals seam like extra complexity without any real benefit. What am I missing?

On a side note, I have some parts you might be interested in that might be perfect for this project. These are from a 2010 Zero, so probably set up for similar vehicle weight and travel to what you're building. Just thought I'd mention since these are in need of an appropriate project..

20210108_161711 by andbike, on Flickr

 

[gixxerjeff]