Roadmaster mtn. sport shifter build

Discussion in 'Motorized Mountain Bikes and Road Bikes' started by xXNightRiderXx, Jul 13, 2017.

  1. xXNightRiderXx

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    Hey there motorbicyclers, I just got done installing the old version of sbps shift kit onto a new chinagirl. This time, parts in the kit seem to be of a much higher quality than they were a year ago, and the kit was the same price. I installed this whole setup onto a roadmaster mtn sport, with a few issues with hardware. The 36t chainring is too wide to fit my 6 speed chain, so I need to grind the teeth down 1/16".
    I need to purchase a single speed chain as that is what was included with the shift kit, but the current one is three links short.
    I need to also purchase a chain breaker to cut the engine chain to size, as once again, the chain that came with the kit is short, this time by two links.
    An offset manifold is required, as the frame is so small, the engine fills 85% of it. I also need to purchase a braided fuel line and make a heat shield because the line, with the tank all the way forward, comes in contact with the head.
    I installed a pull starter for this application, and this one has a metal cable, and seems rugged enough. I gave it a few pulls, and it turns the engine just fine. Used it to test for spark.
    i also need to buy new pedals because the old ones dont flipping fit! One piece to three piece conversion.
     
  2. xXNightRiderXx

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    OK, so I put a rubber hose on my intake as a temporary fix until I can get the offset intake. It is a 3/4" ID hose. This is just to get the engine started to make sure everything works as it should.
    I will be acquiring a micrometer so my father can help bore out the cylinder to add 10-20ccs. I will also be port matching and polishing. Just so everyone knows, my father will be doing most of that work because he knows how to do it.
    The boring and porting will be done twenty days from now. This is going to be an interesting project as I don't think anyone has dared bore one of these engines out. If so, please refer me to the source.
    I lost my torque wrench, so at the moment, I am unable to lap the head.

    If there are any suggestions, please place "suggestion" in the title box. Opinions, just reply please.
     
  3. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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  4. xXNightRiderXx

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    That's on hold at the moment. Right now, I'll be focusing on building these roadmaster shifters, and I'll be saving to get a stick welder and jig. I'll be building that frame myself so it'll only be about $300 in materials.
     
  5. xseler

    xseler Well-Known Member

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    I guess I didn't realize that someone sold oversize pistons for these little engines............
     
  6. xXNightRiderXx

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    When you're only shaving .03mm or less off the cylinder wall, you only need rings. This is coming from my father, a trained auto mechanic who also bored out his cobalt's engine himself.
     
  7. xXNightRiderXx

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    OK, so I'm having a few issues with this thing. The shaft drive chain keeps jumping off the chainring under pedal power, but under engine power, it stays on. I have the idler pulley that comes with the engine mounted to the clutch side bearing plate providing the tension to keep it on while under engine power.
     
  8. xXNightRiderXx

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    OK, so here's the skinny. I bought a half link to prevent the main drive chain from bunching up and falling off the sprocket. The shaft drive chain was misaligned, so i adjusted the position of the 10t sprocket to realign it. I no longer have jumping issues under engine power. I will be placing the pedals inline so they become foot rests. The seat shall be dropped so I can remain seated while stopped. I expect a top speed of 45 mph when the half link arrives. I get 10 mph in first gear. I will also be purchasing a proper right side tensioner for this setup. Will be posting pictures when possible. Will also post actual top speed and estimated rpm at speed before and after boring. I will do this same thing with a Kent roadtech 4 stroker, also boring out the cylinder.
     
  9. tiendatsq

    tiendatsq New Member

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    I think this is a rather large engine and consumes a lot of raw materials
     
  10. xXNightRiderXx

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    66cc engines are not very big at all. I'm boring it out to gain an extra 10-20cc's. Ive started this engine about twenty times and revved it for about two minutes each time and haven't even consumed one tank. I have a half link arriving tomorrow, so I will be able to post range and top speed.
     
  11. xXNightRiderXx

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    Update: got the chains behaving, and I get 20 mph out of third gear, maybe 25 out of fourth. I haven't been able to properly measure speeds, so these numbers are estimates, based on the feel.
     
  12. xXNightRiderXx

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    So, I've been having problems with my pull starter. The cable keeps breaking at the handle, where its knotted around a nut inside the handle. Is there any good and cheap way around this issue?
     
  13. xXNightRiderXx

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    OK, so I got the entire thing behaving how it should, and I got a speedometer. It goes a max of 29.4 mph. 12 mph first gear. I will be slightly increasing the size of both the right side sprocket and the inside chainring to gain a bit more speed, while sacrificing torque.
     
  14. xXNightRiderXx

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    I haven't posted here in a while, so here's what's gone on with my bike since my last post:
    I wrecked it, bending the front fork and totaling the wheel. Moved the kits over to a mongoose threshold. This allowed me to take the hose off, which improved performance. Decided to go camping, and broke two chains. One I was able to fix, but the other stranded me. I got an expansion chamber, which allows me to get 16 mph out of first gear. The performance carb I got causes it to four stroke, don't know how to fix that other than rejetting. I also purchased a boost bottle and an offset intake with a fitting for the hose. Still waiting on the intake. I will soon have this damn thing ported and polished, along with half link chains installed for proper tension.
     
  15. xXNightRiderXx

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    ok, so i got the 79cc monster 90 kit, and the sbp 4s shift kit, and i can't get the engine to fit. im going to try inverting the shaft plate to see if that allows the engine to actually sit on the mount. is there anything else i can try without modifying the frame?
     

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