Chain falls off?

[coppinskier]

I recently got a motorized bike from a friend, and he has never had problems with it, but when when i ride it, depending on the try, when i press the clutch, the chain falls off, or when i stop, the chain pops of. The chain is definitely tight enough, heck, everything should be tight enough. I don't know if this is important but it makes the rear tire not work till i fix it, which sometimes meaning i have to carry it home since its jammed. Also, i have suspicions that its the tires fault since its kind of wobbly. Any ideas will help. I'm new to this so try to be explanatory!

Thanks!

 

[2door]

Chain tension and sprocket/chain alignment MUST be perfect. The chain can be too tight. You'll want 1/2 to 3/4" of slack. If the sprockets and the chain don't run in an absolutely straight line you'll have the problems you're having.

Question: Is there a chain tensioner involved? If so, it too must be aligned with the chain and sprockets.

Tom

 

[crassius]

if the wheel is wobbly, I'd try adjusting the wheel bearings

 

[coppinskier]

Thanks! I will go try that and tell you if it worked!

 

[coppinskier]

Do I need to replace the wheel, or wheel bearings? how important is that?

 

[maniac57]

Do I need to replace the wheel, or wheel bearings? how important is that?

Google Sheldon Brown for all the bicycle repair info you could ever want.
He da man!

 

[missle3944]

Ya my chain seems to be going from tight to loose so I need to re align my sprocket. To top that off I'm pretty sure my sprocket and engine are not aligned either.

 

[Dan]

A real good and simple way to check is just walk the bike and watch for wobble and listen. "Clink, clink, clunk" sounds mark an unhappy spot.

I have used a grease pencil to mark on the sprocket.

Just part of the fun, eh?
(really is fun though)

 

[missle3944]

Ya that seems to be the case with me. The chain goes from being really tight to having slack

 

[Dave31]

Before I ever ride a bike I always have my bike up on the stand during assembly and I always pedal the bike by hand forward and backwards. If I hear any popping, or the chain does not roll smoothly that bike never comes off the stand until the chain, tensioner,and sprocket is all working smoothly.

I don't just spin forward and backwards a little, I really crank that sucker as good as can both forward and backwards for several minutes. If the chain dont pop, rub the engine, tensioner and sprocket mounted correctly you'll have no problems other then if you use the chain provided in the kits.

 

[crassius]

Ya that seems to be the case with me. The chain goes from being really tight to having slack

you'll rarely get it perfect, so it is important to set the tensioner while the chain is at its tightest part of the run

 

[missle3944]

Today I'm going to remount the sprocket and flip it around so the chain will be more aligned with the engine sprocket. I also need to re center it a bit better because the sprocket raises up and down.

Is that what is causing the chain to go from loose to string tight?

 

[2door]

Today I'm going to remount the sprocket and flip it around so the chain will be more aligned with the engine sprocket. I also need to re center it a bit better because the sprocket raises up and down.

Is that what is causing the chain to go from loose to string tight?

Yes! If the rear sprocket isn't concentric with the wheel's hub the chain will tighten then loosen as the sprocket rotates in an egg shaped circle instead of spinning true.

Suspend the rear wheel off the floor, disengage the clutch then slowly rotate the rear wheel and watch the chain/sprocket. You should see what happens if the sprocket isn't perfectly centered on the rear hub.

Tom

 

[missle3944]

Thanks 2 door. What should I use to keep the rear wheel elevated? I don't have a bike mount or anything.

 

[crassius]

must be a 1000 ways - easiest would be take wheel off and put it on another bike turned upside down, but just putting the axle between two chairs will work too - with wheel on the bike, a rope from ceiling beam will hold it

note: when trying to center it, a good way is to put a bolt or drill bit in valley between teeth so that it stands taller than the teeth, that way you can smack it with a hammer without mushrooming the teeth

 

[2door]

How about a rope from the ceiling.

Tom

 

[dodge dude94]

I'm pretty sure you need to make sure the engine is tight, straight, mostly inline with the rear sprocket. Then make sure the sprocket is straight. I think that sums up this thread.



Then Mr. Drivetrain expert comes in....

 

[dodge dude94]

I've never had an issue with my ragjoint.


EVER.

Maybe you have, maybe other people have. But in my experience, it's all about attention to detail. If you pay attention, chit don't happen. And you will also find that a majority of builders on HERE will say it's a great idea, but not necessary.


Additionally, by telling people, that are just starting out that don't even know if they want to continue with the hobby, that they need to spend ANOTHER $65 to buy a hub adapter so they don't get killed is ludicrous. It's not necessary when all you need is something that's free: PATIENCE. That's it. I will admit that with my build I got ahead of myself and it came back rather quickly and bit me in the ass. You really can't just slap one of these kits together, I mean, you can, but it won't work well. Does a hub adapter make it easy to mount the drive sprocket on the hub? Hel1 yeah it does. But does it make THAT much of a difference, if you know what you're doing, to effect performance and safety? Not really.

I don't wanna sound like a total turd here but you're REALLY starting to lose standing with a bunch of the membership when you're running around preaching the hub adapters...not all of us have the extra cash to replace something that will work. Some of us are having to spend that money on stuff to keep the ENGINE going.

 

[2door]

I guess I see some humor in this contradiction. My experience is diametrically opposed to karryhunt's. I currently have four running bikes and I've built several others that I have either sold or given to friends. All but one have used the 'rag joint' and all of them are still running, still have true and tight spokes, the chains don't fall off, the sprockets have never moved and chain tension and alignment have never been an issue.

The one bike with the sprocket adapter runs fine, no chain problems and it took me all of twenty minutes to install the rear sprocket. However...that bike has a roughness to the ride that I couldn't pin down. It is the same bike/frame/tires/engine and mounts as another one that uses a rag joint. I was curious and switched rear wheels on these two bikes. The rough ride followed the adapter. Its as if I can feel the chain engaging the sprocket teeth. Yes, my tension and alignment are right on so the difference in feel is definitely from the solid attachment of the adapter to the rear hub without the cushioning effect of the rubber in the rag joint.

The roughness is noticable enough that I'm going to remove the $80.00 adapter and install a rag on this bike. By the way, its the black chopper in my profile photo album.

I'm sure by now karry is cringing at that prospect.

Tom

 

[fatdaddy]

I'll go either way you want me to build it for you. I like adapters for the ease of installation and rag joints for price. My only concern with a rag joint is using too small of a spoke. I recommend at least a 12 guage spoke if you're using a rag. A larger spoke is better. But for the new guy that hasn't thought this through, and puts a rag joint on some 14 guage (or smaller?) spokes might run into some problems. So I think spoke size has to be part of the equation when considering which way to go.
AND, I'm getting old and loosing ALL of my patience, So I use adapters on my personal bikes. But I darned sho will install yer rag joint fer ya, For a price.
fatdaddy.