Sprockets Space in Rag Joint & Chain Resistance

[jeffreybrown]

Hi all! I've just motorized a cheap $20 thrift store bicycle with one of the 2 stroke kits from BikeBerry. The build went pretty well, and I've yet to test it make sure it runs.

Anyway, when I assembled the rag joint for the sprocket on the rear wheel, because of the design of the hub, the sprocket is just barely unable to sit against the spokes. As such, there's a good bit of room between the spokes and the sprocket. The inner rubber piece (closer to the sprocket & chain), which sits between them, is more or less loose. Based on looks and hand feel, the sprocket seems very sturdy, but part of me thinks this may put too much stress on the bolts while riding.

I could widen the sprocket's center hole, but I certainly don't have the tools to do so properly, and I don't want to mess with the sprocket's radial alignment and centering. The sprocket not being able to fit over the hub actually makes aligning the sprocket very easy, as it rests on a tapered portion of the hub. In any case, if the current configuration is acceptable, it'd be best to leave it that way.

I'm also curious how tight those bolts should be, especially in my scenario. They only felt between snug and tight with the wrench. However, when I try to move the sprocket with my hand, it feels rock solid.

I've noticed that even with the clutch disengaged, there is still a decent bit of resistance in turning the rear wheel. It definitely doesn't freewheel like it would on a regular bicycle! The bike is easy to push though. I guess I'd imagine this is probably normal. I also imagine the chain needs a bit of time to stretch and the sprockets need time to wear down.

If I get this thing working, it should be fun for my camping trip! That's my main planned use for it. I'll be camping at just over 9,000 feet, so I hope the carburetor stays happy. I don't really plan to ride it off road, there's a lot of deserted dirt roads in the area.

Thanks in advance for any advise on the sprocket or such.

 

[motorizedbikeguy]

You want to bolts to be pretty snug, but be careful about over-tightening and messing up the threads. You kinda have to go by feel and use your best judgement.

If you have the money, I would strongly suggest scrapping the default sprocket and going with a CNC hub adapter setup. it's much easier, more reliable, easier on your wheel (if installed properly) and more rigid than the default. I now consider it a mandatory upgrade for any build. Just avoid the kind that uses a hose clamp and the default sprocket.

Some amount of resistance is normal because you're no longer just spinning a bicycle wheel.

 

[bakaneko]

you would want the bolts tight and the rubber rag joint flattened and tight along the spokes. the engine will put tremendous force against that assembly and any wiggle will damage your wheel. i think the default bolts might be okay like that, but again they and the rag joint must be extremely tight. also, if you notice that they are starting to give (bend) you can always replace them with high grade or steel bolts. it wont cost much to replace them.

 

[Frankenstein]

I'd give it a shot at finding a disk brake compatible hub, that or get a friend with a heavy grit sanding drum for a dremel or similar tool to open that sprocket up. I wouldn't though if it's actually perfectly aligned, and see if there's a better solution or if what you have will work no problem.

9k feet... Bring some extra jets or be ready to run a bit rich (not that bad.) I would be careful about using the bike anywhere that's designated as state park land, as you generally can't use anything with an engine in it while in state parks and most reserves.

 

[crassius]

on old machine right now & can't see pic well, but center hole in sprocket has no bearing on alignment - one could hog it out square if they wanted and make no difference in getting it to sit true

I use a half-round file to hog them out when they're too small.

 

[Frankenstein]

on old machine right now & can't see pic well, but center hole in sprocket has no bearing on alignment - one could hog it out square if they wanted and make no difference in getting it to sit true

I use a half-round file to hog them out when they're too small.

Those are a good tool to have in general, you can get a flat and half round for dirt cheap, and they can solve hundreds of problems quickly in an experts hands. Really nice when that old screwdriver rounds out again, works on flatheads and philips

 

[jeffreybrown]

Wow, thanks for all the great replies! Lots of great information.

You want to bolts to be pretty snug, but be careful about over-tightening and messing up the threads. You kinda have to go by feel and use your best judgement.

you would want the bolts tight and the rubber rag joint flattened and tight along the spokes.

Gotcha. I've had an idea: perhaps I can make some cardboard cutouts, the same shape as those rubber pieces, and sandwich several of them in there. I suppose that would be much like increasing the thickness of the inner rubber piece, I'd just have to use several layers and keep it away from water. And then that way I could keep the sprocket resting on the tapered edge of the hub.

9k feet... Bring some extra jets or be ready to run a bit rich (not that bad.)

Okay. I am thinking I should buy one of those jet kits. Do you think the e clip setting on the throttle/fuel pin would be enough to lean it up? Or is that more of a fine adjustment?

I would be careful about using the bike anywhere that's designated as state park land

Indeed. These back roads serve only as access to a bunch of privately owned (but otherwise vacant) lots, basically an undeveloped subdivision.

 

[bakaneko]

dont u cardboard. th might be okay. just tighten down hard. replace bolt wiith stronnger ones if you see bending

 

[gary55]

Wow, thanks for all the great replies! Lots of great information.



Gotcha. I've had an idea: perhaps I can make some cardboard cutouts, the same shape as those rubber pieces, and sandwich several of them in there. I suppose that would be much like increasing the thickness of the inner rubber piece, I'd just have to use several layers and keep it away from water. And then that way I could keep the sprocket resting on the tapered edge of the hub.

Okay. I am thinking I should buy one of those jet kits. Do you think the e clip setting on the throttle/fuel pin would be enough to lean it up? Or is that more of a fine adjustment?

Indeed. These back roads serve only as access to a bunch of privately owned (but otherwise vacant) lots, basically an undeveloped subdivision.

You can get another rubber spacer for 9.00 on ebay. I am at 5400 ft. and rejet NT's with a #68. At 9000 you should get a #66 and a #64 to find the sweet spot.

 

[Timbone]

Jeffrey, I think Crassius has the right answer. You have to file out the center hole on the sprocket so that it can settle into the wheel. Files are cheap. Once you draw that sprocket inward to the spokes then you can get adequate tension on your rag joint.