Off center bicycle motor sprockets.

Bikeguy Joe

Bikeguy Joe

Godfather of Motorized Bicycles
O.K., a quick one here.....

How many of you have had trouble getting the sprocket that came with your bicycle engine kit centered on the wheel?

Not side to side run out, but centered so the chain remains one tension as you move the bike?

Norman mentioned that some of the holes were drilled off-center before. I had trouble with both of the kits I built- never checked the hole for accuracy, I always assumed it was because I used coaster brake wheels and the hole in the sprocket was larger than the hub, thus I never got it centered....even after what seemed like a hundred tries.

Let's hear it!
 
the sprocket on my motorized bicycle is not centered. drives me nuts for i keep trying to get it centered. my next build i am going to try one of kings sprockets made be andy and they are drilled to mount on the rim where you put your disk for a disk brake. i will let you know how it goes
 
This is a royal pain..probably the biggest one related to these kits, IMO. Sometimes they go on centered the first try, and others never seem to center. I can tell you I've had better luck with the 36t sprockets and the smaller diameter 44t sprockets. Perhaps smaller diameter sprockets are more forgiving...just a guess.

Just to rant...I HATE HAVING TO TWEEK THE SPROCKET.
 
Well, I got one of the bikes I sold back and am in the process of rebuilding it (the bicycle motor works fine, the bike itself is hurtin') so I'm going to check the hole and see if it was drilled off center like Norman had mentioned.

I also got a 36T from that'sdax and it looks to be of 100% better quality than the stock sprocket. I'll measure the hole and see if it's centered too.
 
Mine were both off enough that when the chain was at it's tightest, I'd have 3/4" of play, then at it's loosest, 1".

They both were noisy but I couldn't tell as far as motorized bike performance....just noisy!

These next few builds I will see what I can do (if needed) to center them better.

Also, I will be hard at work on a simple tensioner (spring loaded).
 
I checked my sprocket and it seems to be drilled correctly, and it fits very tightly around the dustcap, so I believe it is centered, although the chain goes from very tight to very loose. I was thinking that possibly the chrome might have been applied too heavy on one edge. Beacause I have a 50t chromed sprocket I think just a minimal extra amount of chrome between the teeth would make a big difference. I have marked what I think is the "high" side, and was thinking about trying to grind in between the teeth. Any thoughts would be appreciated.
 
If you measure from the teeth to the outter edge of the hole in several places, you'll find out if it's the center hole or the teeth.

If you have a steady hand and lots of patients, plus the right sized stone for your dremel tool you may grind it until it's "true".

Lotta work though.
 
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Well, I just measured three different sprockets, all of differing sizes and they are all withnin 1/32" or closer....much just be me.
 
Well grinding off the chrome helped a little bit. A spring tensioner, some all thread, nuts, bolts, and washers from Tractor Supply took care of the rest....
Not sure this is the correct place to post this, but here it is......
 

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You wanna tell us exactly how you made it, and how it works in the long run?

That's "Classic posts" worthy.
 
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