The Dirty Dirt Bike – Suzuki RM125 – Done for Now

Here’s the final installment of the relatively simple Suzuki RM125 dirt bike conversion.

Screen shot 2013-09-27 at 10.04.41 AM

The setup uses the same battery module rack and holder as the other bike, with, in this case, a 40V 20ah Headway pack.  To get it serviceable I had to get a new rear sprocket so I got the biggest one I could – a 51 tooth, with a 12-tooth on the front.  I also had to get a rear drum – the best answer to fixing everything that was wrong with the existing one, and a steal at $20 on eBay.

Screen shot 2013-09-27 at 10.04.54 AM

Here you can see the newly covered seat, too.

So yeah, it’s hilarious to ride, as I’d hoped.  As it is, it’s great for low-speed tooling around, but to get it up to the original gas bike performance I need to run it at 80V.  Then, even with that little Briggs ETEK I think I’d be poppin’ wheelies and stuff.  When I do that, I definitely have to go with a proper contactor, with, of course, a bigger better controller.

Screen shot 2013-09-27 at 10.17.23 AM

Remarkably, the really simple motor mount is solid as a rock, with only two mount points, but pulling directly opposite the pull of the chain.  The battery rack you can barely see here works like a champ, too, and I can fit in one of the CALB 40ah packs if I want to.

…but for now it’s done.  A hell of a lot of fun for a project dubbed “Spare Parts”!

OH!  That’s right!

The mail came…  one little addition:

Screen shot 2013-09-27 at 1.09.34 PM


5 responses to “The Dirty Dirt Bike – Suzuki RM125 – Done for Now

    • Well, the idea was to use the spare stuff I had kicking around, so spend as little as possible. I bought the bike for $100 (in one of the sketchiest deals involving a motorcycle sale I’ve ever been partly to… lol!), I got a chain for $20, a hub and a sprocket for about $20 each. The seat was $10.

      It’s a Curtis 36V controller with a Magura throttle and 24 Headway 10ah cells and those holders… I don’t know how much that stuff goes for, to be honest, but they were all picked up used from a buddy for another project. There’s no contactor. Oh and a new front tire from Craigslist (used) for $10. 😉

    • Warehouse, outskirts of town, late at night, a bunch of guys standing around, me with a pocket full of cash… “…oh, you must be the guy about the motorcycle. It’s in the cellar. Joey, show the guy that dirt bike”. I felt like I’d have been safer if I was trying to buy crack.

      A contactor is your safety. It’s a high voltage, high current relay controlled by low voltage and current, and is designed to let you break the circuit if it’s running wild. With any more than the 36V I’m running (actually 40V) I’d be really worried to not have one. Right now I switch it with one of those cheap battery cutoff paddle switches, but I’ve fused those, even with only 36V, when it’s switching the motor under load.

      Here’s a little more:


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