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Old 04-27-2013, 06:43 AM
Nashville Kat's Avatar
Nashville Kat Nashville Kat is offline
Motorized Bicycle Elite Member
Join Date: Apr 2009
Location: Jacksonville, Florida
Posts: 1,403
Default Re: Bottom Bracket Coversion Kit

Um, if you are converting to a 3 piece crank, you obviously need the crank-

It sounds to me as if someone gave you some bad info because a 2 stroke China Girl motor will fit between most normal cranks and axles both 1 and 3 piece- unless you have a pull start and centrifical clutch. You can get wider crank spindles for three piece setups- I think Sick Bikes sells some. Most 4 strokes need wider cranks.

the advantage is that an alloy 3 speed crank generally weighs much less than a steel one piece crank-

The weight difference may or may not be that important on a motorized bike- it is to me though and I have two builds both converted and with a single alloy sprocket on alloy 3 piece cranks.

You can get a nice annodized single gear 3 piece alloy crank for about $40 and up- so with the conversion it's a little pricey- I use vintage cranks I got on ebay cheap.

You can also go to a much smaller sprocket on your steel crank- even alloy-
and a small gear not only gives an easy pedal, but can save a lot of chain link weight- to even difference between that and a 3 piece alloy set-up

The conversion brackets like yours came along in the BMX days at the dawn of the 1980's- the three piece cranks are not only lighter, the bottom brackets have smaller and lighter bearings, except the older style which stilll use the one piece bearing sizes-

If you have a 3 piece spindle you also have the option of using featherweight titanium crank bolts- I got some for about $10 a few years back, but maybe the prices are up- don't know.

Can you post a link or links to your kit or the conversion kit? (Highlight the page address in your browser and copy it to clip, and then paste it in your post) That might make responses more accurate.

Last edited by Nashville Kat; 04-27-2013 at 06:51 AM.
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