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Norm's 2 stroke repair center Having problems with your 2 stroke motorized bicycle engine? Just ask Norm, he loves to tinker and troubleshoot engines


44 to 36 tooth sprocket swap on motorized bicycle

Having problems with your 2 stroke motorized bicycle engine? Just ask Norm, he loves to tinker and troubleshoot engines


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  #1  
Old 02-24-2008, 06:45 PM
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Default 44 to 36 tooth sprocket swap on motorized bicycle

part 1

1. Wheel off the bike and mounted in the vice so its easier to work on. The 36 tooth new sprocket is laying on the bench, ready to go on after truing up the center hole which was 1/8" off center


2. I cheat when I can to make it go easier using an air rachet to get the bolts off. Yes the rachet isn't on the bolt I'm taking the pictures and doing the work Rufus is taking the day off again something about union rules and Sunday.

3. All parts are off I'm holding the fiber washer that goes inside the spokes it is the only one that gets cut. I'm reusing all mounting hardware
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  #2  
Old 02-24-2008, 06:53 PM
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Default Re: 44 to 36 tooth sprocket swap

part 2


1. Making sure the sprocket fits with a little slop and not tight on the hub. Use the dremel if its a little tight on the center hole.


2. I'm putting the inside fiber washer in place. I cleaned off the hub and spoke area and checked for loose or broken spokes none were so I'm good to go.


3. This is the outter fiber washer resting in place.
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  #3  
Old 02-24-2008, 07:04 PM
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Default Re: 44 to 36 tooth sprocket swap

part 3


1. The sprocket goes on next eyeball through the bolt holes so all bolts will go through with out hitting the spokes rotate the sprocket until you get it right. In this picture is not quite there yet.



2. How to get the nuts on working around the spokes. I put on all three backing plates and one bolt in each center hole of the backing plates and tighten lightly then all the rest of the bolts washers and nuts get put on but not tight yet.


3. Here is what it looks like with all hardware in place. Make sure the backing plates are all even and not over lapping on each other.
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  #4  
Old 02-24-2008, 07:25 PM
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Default Re: 44 to 36 tooth sprocket swap

part 4


1. I put some blue dry marker ink on the 3 bolts and the screwdriver is Pointing at these 3 bolts they are in the center of the 3 backing plates I tighten these first while watching the backing plates so they won't over lap each other. Then I start tightening the rest of the bolts, I also check the trueness of the sprocket as I go up and down and side to side wobble. I try to get all up and down slop out and side to side to around no more than 0.015 play.


2. Look close, you will see a wire pointer I'm using as a guide to true up the sprocket As I spin the wheel I don't want the gap between the wire and the teeth to change. The sprocket is marked with blue dry marker ink and the pointer wire is next to it. I have the wheel mounted in the vice by its axle and griping the axle on the axles nut so I don't damage the threads on the axle.

3. You can see the pointer wire against the blue funnel in the back ground. The pointer wire is mounted on a strap of flat strap and clamped to a shelf in the back ground and not hanging in the air by magic. Look close and you will see the bolts are sucked up quite a bit in this picture.
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  #5  
Old 02-24-2008, 07:39 PM
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Default Re: 44 to 36 tooth sprocket swap

part 5

1. I have the dial indicator mounted on the iron strap and the dials stylis on the sprocket checking for side to side wobble once the up and down wobble is gone which I used the wire and eyeball method to true. I should have taken a picture of the strap from the side so you could see it better as to how it was done. The dial is on 0.000 here


2. The max side to side wobble is kept at 0.015 in this picture. Most of the wobble is adjusted out by tightening the high spot bolts


3. The difference in 44 and 36 tooth sprockets. Rufus likes to play with the drill incase you are wondering why the sprocket has so many holes
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  #6  
Old 02-24-2008, 08:06 PM
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Default Re: 44 to 36 tooth sprocket swap

Norm How did you measure to find that the hole was off center?
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Old 02-24-2008, 08:18 PM
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Default Re: 44 to 36 tooth sprocket swap

part 6


This picture shows how it all looks after all bolts are tight and the sprocket is trued up the chain is shortened and back on the bike. All I now need to do is put the guard back on and test ride.
I got it up to 38 mph and chickened out. But the engine speed in the 20 mph range is very nice and smooth just about 1/8 throttle and I motor along. It really lowered the cursing rpms. I can still let the clutch out almost from a stand still and motor away.
I did not go into great detail on this but you all should get an idea on how to mount the rear sprockets and true it up. I used the 3/8" drive air ratchet set at 80 psi tighten up all bolts until it stalled then I used my 1/4" drive hand ratchet to tighten up the bolts when truing the sprocket along with the 10 mm end wrench. This compressed the fiber washer tightly against the spokes and sprocket so nothing will wiggle loose I hope. That's it.
Rufus now wants me to rub his fur backwards and then start taking the engine apart for the wrist pin replacement. He said he will let me play with the new 36 tooth sprocket for a few days before I tear into the engine. Man what a nice kitty.
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  #8  
Old 02-24-2008, 08:29 PM
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Default Re: 44 to 36 tooth sprocket swap

part 6

measuring in an X pattern from the end of the teeth to the edge of the hole. I then bolted a good sprocket to the 36 tooth sprocket and compared them and then scribed the 36 tooth where I would need to remove material which I used a dremel tool to remove the excess material. I then mounted the sprocket on a machined shaft in the lathe to see if and when it was true I then checked that there is a small amount of slop or space between the inside edge of the sprocket hole and the bikes hub so I could center it up while getting the bolts tightened up that is where I used the wire to align the sprocket on the bikes hub to get the up and down play out of the sprocket this is more important than the side to side play because the up and down play will make the chain be tight then slack.
Norman

Last edited by Norman; 05-31-2009 at 10:51 PM.
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