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Another pocket bike motor conversion

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  • Another pocket bike motor conversion

    Here's another one on the go...

  • #2
    All tacked together to check fitment and clearances etc.

    It was a geo bigfoot, but I've converted it to chain drive and I'm building this ported 49cc motor for it. I've done this type of thing before and it turned out pretty sweet. This will get prettier up once I get it going.

    here's my last one with motor mounted above the rear wheel. This works, but does put a lot more stress on the cantilevered axle by pulling on the sprocket on the lefthand side (open end of cantilever). My latest one is more like a factory goped with the motor to the side, which then has the sprocket on the righthand side and hence less stress on the axle.


    • #3
      Great work! I'm. Urious on the performance results with the port work and the pipe.
      2 Sports and a GSR40


      • #4
        Originally posted by Turbobox View Post
        Great work! I'm. Urious on the performance results with the port work and the pipe.
        It'll never be like a 6.5hp polini or blata motor, but at a guess I think around 4hp? It moves it along quite well, and for minimal cost to build.

        I live in New Zealand, so getting parts for gopeds (or anything like that) is somewhat difficult. Freight cost per item is often an additional $50-$100 just to get stuff sent here. So you have to improvise in order to get stuff done.

        These Chinese pocket bikes are fairly common here, due to free shipping from Ebay or Ali Express. So you can pick up a secona hand motor for $20. Add an Ebay big bore kit and do some porting and it wakes these motors up!

        I'm still learning from every motor I make. I've done about 10 of these now and still trying out different ideas. Not all my ideas have added power...but that's the price of education


        • #5
          Nice build. Keep up the good work.


          • #6
            Here's a small update. It's been on the back burner for a while...

            And all running sweet...



            • #7
              And the motors all together now.


              • #8
                Wonderful! I can't wait to see it on the road!
                2 Sports and a GSR40


                • #9
                  Nearly finished. A few loose ends to tidy up, then stripping it down for paint.


                  • #10
                    2 Sports and a GSR40


                    • #11
                      I've basically finished it to get it rideable. I'll ride it like this for a little while to find any issues and then fix those. Afterwards I'll start to add some nice billet bits for looks. The go fast stuff has already been done, so it's just purely cosmetic stuff.


                      • #12
                        All finished.

                        This was my first start up and ride, it was running way too lean in this vid. I've tuned it and got some fairly respectable power out of it now.


                        Has torque to burn, pulling hard anywhere in the rev range.


                        • #13
                          All tuned and dialed in.


                          Got heaps of torque, keeps popping the front wheel up. Very sketchy to ride with fat tyres and tiny handlebars. I'm going to change a few things to try get some better handling characteristics.


                          • #14
                            Got it humming now! More tuning and oiling the chain made a massive difference. Seriously, I assumed the chain would be well oiled being brand new. But in free wheel mode, it felt like the rear brake was on. Took a lot of effort to overcome the friction. I oiled the chain and it seriously made a world of difference...probably 25% more acceleration - no joking around.


                            Goes like a rocket now! On my driveway I'm only touching on powerband, then I'm HARD on the brakes to avoid hitting the house. Front tyre is always on the edge of popping up, so careful throttle control is required. This thing is awesome!!!
                            I put new tyres on it and that dramatically improved handling. The old tyres were flat, from the old spindle driven goped motor. New tyres are nicely rounded and that's a night and day different in handling.
                            So all things considered, I'm stoked with this build. Its had about 4 hours riding (stuck at home with covid19 lockdown) and zero issues. So cool...


                            • #15
                              It sounds like it's just about to hit the powerband when you run out of room haha. Looks fun man!