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Old 05-14-2015, 06:28 PM
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Davezilla Davezilla is offline
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Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: Super Rat -- does a pull start fit?

That would work on a briggs type engine, but there's a risk of bending the crank on one of these since these are cut down to a much smaller shaft diameter where the mag rotor bolts on... Using the rope directly on the mag rotor or a sheave attached to the rotor would put too much side load on the crank when pulled, the end of the crank would need to be supported somehow like making up something similar to the regular china doll pull starter, but if one was to design a support bearing then bolt a small gear to the end of the rotor, a zip starter would be fairly easy to design, the zip starter uses a plastic "zipper" that's basically a piece of flexible or semi rigid plastic with teeth molded in or machined in and a pull handle on one side, the zipper is fed thru and quickly pulled out, the drawback of a zip starter tho is that the zipper needs to be stored on the bike when not in use like while riding or left at home but then you couldn't shut the engine down if you have a centrifugal clutch or a jack shaft where bump starting couldn't be possible.
The other drawback is that the engine can shoot the zipper out if it starts early in the pull.
Feeding the "zipper into the start slot on the side of the engine can be made easy by using a one way bearing to mount the gear to the mag rotor, this could be pressed onto the rotor and the gear pressed onto a one way bearing, then once done this way it couldn't spit out the zipper violently if the engine starts before it's pulled all the way out.

Back to pull starting, the easiest method would be to copy a China doll pull starter but with the right sized case cover, then use a bendix type pawl that would push out and engage with the mag rotor, this eliminates the side load on the mag rotor and retracts out of the way once the engine is started or the rope is released... We could use a CAG start pawl for this since this is how these are designed, now we need a CAG pull starter and a way to mount the recoil and pawl setup to a stock mag cover, and the other half of the pawl to mount to the end of the crank... I got an idea and a CNC router that can make the parts, but not a lot of time to mess with it, but maybe if we use Cag starter parts we can get one successfully built a little quicker...

Still would like to hear some more inputs, but this might be the easiest way to get one made.
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