Thump From Drive Train

[Emmbeedee]

I had originally thought my wheel bearings were bad, so I replaced them though they looked ok, but the noise persisted. So I figured the cush drive rubbers were shot after 80,000 kms but had not yet replaced them. But tonight I had this idea of putting the bike in gear and trying to turn the rear wheel to see if there was a visible amount of play in the hub when lo and behold, the noise came out of the front of the drive chain.

So it turns out the front sprocket was loose!

This was last replaced at about 38,000 by the dealer under the factory chain/sprocket recall.

The front sprocket is hooked now and does need replacement, as does the chain and rear sprocket, of course. But now I know what the cause of the noise is.

[runnin4melife]

That is some seriously promising longevity! Glad you figured it out. Now if I could only figure out why every time I take a motorcycle apart I wind up with extra bolts?!?!?

[Emmbeedee]

Originally Posted by runnin4melife

Now if I could only figure out why every time I take a motorcycle apart I wind up with extra bolts?!?!?

Probably your so called buddies throwing a few extras into the pile.

[mapuda]

Isn't there a locking tab on the front sprocket? It has been awhile since I last changed out my chain & sprocket but most bikes have the tab to keep the counter shaft sprocket from getting loose.

Figure that the dealer would give the chain replacement warranty work to the noob mech.

I had replaced my chain about 10k miles before the recall with a DID Xring.

[Reaver]

Originally Posted by mapuda

Isn't there a locking tab on the front sprocket? It has been awhile since I last changed out my chain & sprocket but most bikes have the tab to keep the counter shaft sprocket from getting loose.

Figure that the dealer would give the chain replacement warranty work to the noob mech.

Wise Guy eh? Why I otta! I replaced a butt load of chain/sprockets under warranty as a n00b. Low tech really. The bolt on the sprocket is like a cymbal, called a Belleville washer in aviation anyway. Wikipedia The singles use a bend over lock tab.

So not to blame anyone, over 40k kms without checking the bolt for tightness?? For shame! Sprocket hooked? Oops, forgot to look! Must've been "Procrashtinating!"

[kelsow]

Glad to hear you found out your problem.

Ever since I owned a drz400, I have been putting locktite on the front sprocket splines.
It's a bit of a biotch to get off but not a huge job in return for piece of mind.

I usually ride with the plastic cover removed to keep an eye on the sprocket.

[Emmbeedee]

Originally Posted by kelsow

Glad to hear you found out your problem.

Ever since I owned a drz400, I have been putting locktite on the front sprocket splines.
It's a bit of a biotch to get off but not a huge job in return for piece of mind.

I usually ride with the plastic cover removed to keep an eye on the sprocket.

Good idea putting Loctite on there. That's what I plan to do. I have some Bearing Mount 620 I hope will be appropriate for the job.

[Emmbeedee]

Originally Posted by Reaver

Wise Guy eh? Why I otta! I replaced a butt load of chain/sprockets under warranty as a n00b. Low tech really. The bolt on the sprocket is like a cymbal, called a Belleville washer in aviation anyway. Wikipedia The singles use a bend over lock tab.

So not to blame anyone, over 40k kms without checking the bolt for tightness?? For shame! Sprocket hooked? Oops, forgot to look! Must've been "Procrashtinating!"

Why would I check the bolt for tightness? If they'd done the job right, using Loctite to hold the bolt in, would I reasonably expect it to need checking? If it was Loctited properly, checking it would break the bond anyway.

We normally get 40,000 out of sprockets and chains, but they're usually hooked slightly by the end of life. I plan to get a little more out of this one though since it's not badly hooked.

[JRWooden]

Rev. #4 of the BMW manual (they are now up to at least rev. #6 but I don't have it... )
calls for locktite #243 on the front sprocket bolt, with torque of 50Nm

On rear sprocket it says to use new nuts (they are some sort of special mechanical locking nuts),
and are to be TTA (Torqued to Angle) 10Nm seating torque, TTA of90 degrees.

But again my manual is potentially down-level ...
You'd think that for $120 I'd get free updates but nooooooooooooo

[Emmbeedee]

Originally Posted by JRWooden

Rev. #4 of the BMW manual (they are now up to at least rev. #6 but I don't have it... )
calls for locktite #243 on the front sprocket bolt, with torque of 50Nm

Thanks for the torque figures. Saves me looking them up.




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[Emmbeedee]

Strange - I was looking at the sprocket today and it almost looks like it has a brass core or something like that.

[Reaver]

Originally Posted by JRWooden

Rev. #4 of the BMW manual (they are now up to at least rev. #6 but I don't have it... )
calls for locktite #243 on the front sprocket bolt, with torque of 50Nm

So does my rev 6???

Emmbeedee, I am not offended nor am trying to offend. All trades have shoddy workers so that is a possibility as well. My point was that ALL your nuts and bolts should be checked at least once a year or more if required. We don't have the safety factor a car does. If there was loctite on the bolt, and torqued correctly to 50 NM, the loctite would require what, maybe 100 NM of force to break? Therefore checking a tight, loctited bolt would not cause it to move unless it was already loose. The copper you see on the sprocket is copper anti-seize. The reason your sprocket was able to be removed after 40k kms, not rusted on solid.

The Bulletin on the chain recall was very specific. Both sprockets and chain, lower shock bolt, rear sprocket bolts and swing arm nut were all replaced. BMW doesn't re-use mechanically locking fasteners (or micro encapsulated) on critical components. The lock washer on the front sprocket bolt IS re-used and the bolt isn't loc-tited. The bolt is anti-seized tho, despite what the maintenance CD's say. I can't explain it. I do know that some front bolts and sprockets could not be removed due to rust. Heating the shaft destroys the seals etc so better it be anti-seized with a tq check now and then. One of the failings of BMW is their paperwork and manuals. Sometimes a person would give up trying to correct conflicting information or just simply find a spec.

Bad flasbacks!

[runnin4melife]

perhaps my days of racing have stuck with me but I safety wire this piece still...

[JRWooden]

Reaver:

The bolt holding in the front sprocket was to be anti-seized?

In Rev #4 of manual it says the rear sprocket NUTS that could not be re-used, but did not mention that the bolts were single-use ... implying that re-using the bolts was OK. I realize it is a TTA fastener so .... yeah I'm confused as usual

And yeah, now the Germans owe me a case of beer damit....

[Reaver]

Originally Posted by runnin4melife

perhaps my days of racing have stuck with me but I safety wire this piece still...

As an Aircraft Mech, I can safety wire anything in 2 minutes. 3 if I'm upside down in the dark. Making holes in non aircraft hardware is a little trickier.

Guess who got to lockwire the Boss's race bikes?