Chain not stayig on sprocket

thatguyjay · Jul 18, 2014

Hey gang. First of all, I want to say I appreciate this resource SO much. I'm not a gear-head but I'm a fast learner and can follow directions. I'm a new old noobie. I gave up on my bike project 2 years ago after a lot of frustration (and bought a ninja 250 motorcycle) but I sold the motorcycle because I never road it on the regular. Gear and tuneups and walking around like a space-man, either too hot or too cold...-whatever I'm over it and I'm ready to crack at my chinese motor beach cruiser again with a new level of determination because it was the last relationship, I mean bike, I really enjoyed.

THE POINT:

So, I've got this problem where after about 2 turns of the drive gear the damn thing jumps off. I've tried adjusting the tension roller / chain guide in but the chain just wants to feed off the sprocket. I'm at a loss. laff

http://youtu.be/n0guGWVPcV4

Kioshk · Jul 19, 2014

WAY too loose @ 00:08. Looks like you could push the axle a bit further back into the drop-out. Also: vid of the sprocket from the REAR.

crassius · Jul 19, 2014

too loose and tensioner has 2 jobs to do - one is to tighten chain, other is to steer chain straight onto rear sprocket - adjust sideways till the sprocket teeth hit exactly in center of chain (I like to grind teeth of sprocket to make them thinner at the tips to help with this, but not absolutely necessary)

CTripps · Jul 19, 2014

Look at it from the back, looking along the top of the drive chain (and throw us a pic if you can). How's the path look? If the chain has to track 'sideways' by more than (someone will chime in with a real number, I'm guessing off the top of my head and going to say about) 3/8" to 1/2" to align between the motor and the sprocket there's a problem. Unlike bicycle chain, the drive chain doesn't have as much sideways flexibility.

Once the chain path is sorted out then you can drop one more link from the chain, or move the idler/'tensioner' to take out the excess slack you have there.

The_Aleman · Jul 19, 2014

Almost every time, what causes a chain to derail off a sprocket is the alignment. It doesn't take much to cause it.

CTripps · Jul 19, 2014

By the way, is your sprocket centered on the hub and 'true' to the wheel? Is the gap between the teeth and the spokes consistent all the way around? Those two issues can also cause problems.

2door · Jul 19, 2014

Here is a little help for you.

Tom

thatguyjay · Jul 19, 2014

You guys have given me a lot to check for, so thanks. There seems like a lot of things that can go wrong in this department!

I've played a lot with the idler, moving it in and out and sideways. I really didn't think this was considered a loose chain!

I think the root issue is that the motor doesn't align real well with the sprocket. I'll get some shots from the rear up later today and hopefully that will narrow down what's causing it.

thatguyjay · Jul 19, 2014

Hey guys, so I took a look, down the site line from the diagram and the motor alignment with the sprocket is not bad.

What is bad is the degraded rubber **** that mounts the drive sprocket to the spokes. This has the sprocket sitting kinda tilted. So, I took off the back tire for now and looking for more reliable drive-sprocket solutions.

Any links to threads or products are welcomed.

That diagram 2-door posted really helped me understand it from another angle (the one that matters)

greaser_monkey_87 · Jul 19, 2014

http://mmbikeparts.com/sprocket_adapter.htm check these guys out. Other vendors sell this product, but charge more.

thatguyjay · Jul 20, 2014

Do you need to buy a new sprocket with these?

2door · Jul 20, 2014

As a rule, yes. The custom sprocket adapters typically require a sprocket made by the same folks. The nine hold kit sprocket can be modified to fit but it is a precision modification that wouldn't be easy to do in a home shop/garage with basic tools.

For the price it would be better to go with the adpater and sprocket as a matched set.

Tom

crassius · Jul 20, 2014

I'm a really good mechanic with over 50 years experience on motorcycles, but the first 4 or 5 of these I did gave me horrible problems with chains & sprockets. I slowed down, and paid much more attention to how these parts all worked, sorted it out, and have had only one problem in all the years since (a guy had bent a tooth on the drive sprocket that I didn't notice till taking it out).

I consider it well worth the effort to redo your chain & sprocket until you have an understanding of them, and never have another problem with the parts as delivered in the kit.

The only really good thing about these kits is the price - doubling your price in after-market parts that only solve problems you are causing yourself seems a terrible waste.

thatguyjay · Jul 20, 2014

Crassius,

I hear ya bro but that rag joint has bothered me since day one. Too many damn screws, every time I adjust it I gotta undo what feels like 1,000 screws after the 3rd time you do it.

I used to see some cheaper things called a pineapple, it was a metal plate carved with grooves for the spokes.

Do they still make those or did they suck too?

2door · Jul 20, 2014

Crassius makes a good point here.

Actuallt there are quite a few builders who use the so called, 'Rag Joint' or kit sprocket adapter and never have issues with them. Once you master installing one and get it set up correctly they are just as reliable as the expensive aftermarket adapters.

The keywords being 'installed correctly'. Yes they take some time and patients to get right.
We haven't asked but you do have a 36 spoke rim, right? Trying to properly install the rag joint on a wheel with 32 spokes isn't going to be easy, or in some cases even possible.

Tom

thatguyjay · Jul 20, 2014

Yep, it's 36 (counted 18 on each side).

It's just a huffy beach cruiser from Big 5.

Maybe I'll buy a replacement mounting kit and give another try. Right now the rubber is degraded and of uneven thickness. I also might have gotten weird metal plates because they overlap and make it even more of a pain to screw in the bolts.

Is that part normal? I can take a picture if I'm not clear of what I'm talking about.

2door · Jul 20, 2014

The plates should not overlap. You will need to spread the bolts after they're in from the sprocket side and through the first, outboard rubber. The second or inboard rubber then goes on and now here's where you'll have to get creative in getting the plates to lay flush against the rubber with no overlapping ends.

Some use a wide screwdriver, I prefer a large set of snap-ring pliers set to spread when squeezed. Whatever works for you but keep after it and you'll eventually get it. Some have suggested tightening one end bolt in a plate then working to get the ends butted and tighten the end bolt in the next plate. I like leaving them both loose and tightening them evenly alternating betwen them until the end of the plate is pulled down snug, ends just touching.

If the plates overlap that can cause uneven pressure in the sprocket/rubber/spoke/rubber sandwich and that will give you a wobble.

If the rubbers are not of consistant thickness, that too can produce a wobble. They can be sanded or ground to the same thickness but buying or making new ones is another option.

Tom

crassius · Jul 20, 2014

also, be sure each of the bolts is going in thru the center of the 9 small triangles made by the spokes just above the hub - that way, as the spokes flex when going around turns, they will help to pull the sprocket back to straight when the turn is done

thatguyjay · Jul 20, 2014

So, I'm definitely learning something here. I'm an economy minded fellow and if pro builders are using the stock unit at a tenth of the price of the aftermarket solution I'm going to listen!

It sounds like my whole approach to the stock rag-joint was incorrect. I'm pretty sure getting the plates to line up end to end while working inside a cage of spokes is going to be a pain! Thinking back to when I did it last time, the rubber seemed quite inflexible as well...

But clearly this is wrong. (Please excuse the cobwebs and the missing nut).

Looks like I'm going to buy new rubbers, because these have a big chunk missing.

Going to give this another shot!

2door · Jul 20, 2014

Yep, I'd say some new rubber would be in line. If one is missing a big hunk you can't expect it to sit flush with the sprocket and the metal plates. And it must.

I'd contact your kit supplier and request they send you a new set of rubber discs. That would be better than trying to fight with what you have.
If that fails you could try using the bad rubber on the inside and the good one next to the sprocket. It's the sprocket that needs to spin true to the wheel and if the spokes are tight and true putting the thicker rubber outboard might get you going.

Tom

Chain not stayig on sprocket

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