Please help diagnose this wheel/drive problem

It started with a *thump* *thump* *thump* coming from my rear wheel when braking at slow speeds. At first I thought it might be the brake. But then I noticed it sometimes occured while accelerating too, though less often.

I took a good look at the brakes. The rotor looked straight, no apparent binding, and I didn't see any problems there.

With the bike on center stand and the tranny in neutral, I rotated the rear wheel. I noticed that at approximatey every 1 1/4 rev of the wheel, I could feel some tension build up and then release. A few times, I thought I heard a faint *click* come from the wheel hub. But it didn't happen frequently enough for me to narrow down the exact source location.

I'm thinking (and hoping) that this is a wheel bearing problem. I just ordered a set of new bearings and seals from Jeff, and am waiting for them to arrive. Does this sound right to you guys, or should I be looking elsewhere. Any thoughts?

What I fear the most is that this is a problem in the transmission or main bearing. I guess I could go ahead and remove the chain, turn the wheel, and see if I still get the rotational hesitation.

Sound like removing the chain is the next step. If it does go away, check your chain for a bound up link.....then worry about the tranny.

Update:

I removed the rear wheel tonight. The bearings definitely need to be replaced. I saw a lot of rust on one side and they didn't roll smoothly.

I found something else at the front sprocket. The nut was very loose. I'm talking finger loose. If it weren't for the lock washer, it would be gone. So I'm thinking that might have also been causing some vibrations that I had noticed.

When the new bearings arrive, I'll get those swapped out, tighten up the front sprocket and see if the noise and thumping goes away.

mariozappa wrote:

Sound like removing the chain is the next step. If it does go away, check your chain for a bound up link.....then worry about the tranny.

I agree, not that what you found is the problem, but check for a tight spot in the chain also. Front sprocket loose??!! Scary...:S

Bluemeanie wrote:

mariozappa wrote:

Sound like removing the chain is the next step. If it does go away, check your chain for a bound up link.....then worry about the tranny.

I agree, not that what you found is the problem, but check for a tight spot in the chain also. Front sprocket loose??!! Scary...:S

I will check the chain.

Yeah, I'm a little baffled as to how the front sprocket nut got loose. The fold-over washer was still there, and although I could rock the nut back and forth with my fingers, I couldn't turn it. The washer was preventing that.

It's almost as if the PO never tightened it all the way, and just locked it in place, loose, with the washer. :blink:

I'm glad you checked everything before you got hurt or damaged the bike. I don't know if the bearing or loose sprocket nut caused the thumping; I agree with mariozappa about the chain and here's how I think it through.

On my bike the rear wheel spins 2.4 times for one complete chain revolution. (102 links / 42 teeth sprocket = 2.4) So your thump every 1-1/4 revs is half that. I think it's a tight link passing over the front and rear sprockets, thump, thump.. just my guess.:silly:

Okay, I took a close look at my chain. It was indeed very stiff in several places. It felt very "gummed up".

Is this something that can be fixed with good cleaning and lube, or do I need a new chain?

What is the best way to clean them, and how can I tell if the chain is no good?

Another question, since my chain is "endless", is there a way to remove it from the bike without breaking it? I assume this means removing the swingarm? Is that a big deal?

jack her up and remove swingarm no big deal,check swingarm bearings while youre in there.soak chain in a bucket of diesel fuel to clean in up,im guessing its probably time for chain and sprockets though.id suggest 530 coversion while you are at it;)

If the chain is stiff in several spots, that's usually indicative of poor/lack of lube and likely rusted rollers.

And yes, the swingarm needs to be removed if you want to remove the chain for cleaning and re-install it in it's original endless condition.
If the nut on the front sprocket was that loose, I'd suggest checking for wear to the sides of the teeth on both sprockets, as it likely was wearing them
down.
I don't know what your budget is, but if it were me I'd replace both sprockets and the chain with an o-ring style chain. This would be the prime opportunity to do the 530 conversion on your bike, which will open up a larger sprocket size selection to you, and knock a few pounds off the bikes total weight to boot.

Since your bike is obviously down until you get the wheel bearings, I'd highly suggest going over the entire bike (EVERY nut/bolt/screw/etc) to see what else the PO may have forgotten to secure properly. :pinch:

I just put a 530 RK x-ring chain and new sprockets on mine, got them from Z1. About $140. If you decide to buy a new chain then also decide if you want to rivet the chain or use a link and clip. I went with the clip because I don't have a lot of horsepower and a clip should be fine, nor did I want to part with another $95 to buy a riveter tool.

This is funny.....NOT!
This weekend, after reading this thread, I was changing the clutch cable on my 77B1. I pulled off the clutch cover to undo the cable end and, guess what?!
MY SPROCKET WAS LOOSE TOO! It still had the washer bent over the nut and would not spin on the shaft, but it WAS loose!
HOLY MOLEY!
It's fixed and all good now, but DAMN! I'm feeling a little lucky!
:sick:

Post edited by: mariozappa, at: 2007/06/18 10:16

OK, so I think I have the same problem(s) listed here. I'll be checking all this in the next couple days on a rear stand. Quick questions: in order to check the front sprocket I'd imagine I take off the front chain cover housing, right? What about the little oil pump cover? Do I need to be prepared with some new gaskets and will oil go all over the place? Basically what is the procedure. I'll check my Clymer tonight, but I thought I would ask for tips here as well.