noob final drive questions!

[potatowedge]

Hi all, I just recently joined this forum because I am doing a custom build of an '81 r65 for a friend of mine. Little did I realize how much there is to learn on these things! I'm very much used to my vintage 2 strokes and XS', so it seems everything is throwing me for a loop.

The latest issue is the final drive. I've stripped down the bike to an engine in frame, and just pulled off the final drive tonight. When I went to drain it, there was a good amount of metal (fine and powdery) on the drain plug. Obviously, this is worrisome, but exactly how bad is it? I should say that there were no strange noises or leaks before I took it apart. The bike has around 70k on it. Also, how difficult should it be to turn the final drive when you have it in your hand?

thanks,

robb

[nhmaf]

Did you take any pics that you could share (I think you have to do a couple of posts before the forum will allow you to post pictures or picture links).

A small amount of very fine 'fuzz' would be OK/expected if the oil hadn't been changed in quite a while.  But, if you feel discernable 'chunks' or sharp point slivers, then that isn't a good sign.

Fortunately, final drives for these aren't tooo hard to find, though you may have to look for a few days.   How much gear oil came out?  Should have been around 350cc

Here is a link to an online copy of the riders manual if you don't already have one, should help quite a bit:
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1271881232

Oh, and welcome to the forum!  Other inmates will arrive shortly...

[Barry]

Welcome Robb

I agree a little smooth paste on the magnetic is not too alarming after high miles but it's fair to say there shoud be far fewer wear particles in a final drive than a gearbox.

Does it turn smoothly by hand ?

[Bob_Roller]

Welcome Robb !!

Remove the fill plug at the top, and the overflow plug at the back of the final drive, check for stripped threads .

Could you tell if the metal particles were iron or aluminum ?

Not too uncommon to have the overflow plug threads strip, someone may have drilled out stripped threads and rethreaded for a larger size plug .

[montmil]

...and exercise caution when refitting the small "fill check" bolt in the rear of the final drive. A gentle snug is adequate. A peek with a flashlight into the threaded hole might reveal a threaded insert from a previous over-torque. Same goes for the bolt securing the ground strap to the gearbox.

BTW, with any small steel bolt going into a tapped and threaded aluminum component on the Airheads, snug is good. Take the shop manual's torque values with a grain of salt.

Glad to have you with us, Robb. We love potato wedges and Shiner beer... plus a photo or two of the bike. [smiley=beer.gif]

Monte

[potatowedge]

Thanks for the replies! I was out of town for a while and totally forgot about this. Anyhow, the metal I found was an extremely fine paste, so that seems like a good thing so far. If i had to guess I would have to guess it was iron by the way it was sticking to the magnetic plug. However it is definitely not easy to turn over by hand...it is extremely tight to turn with just my fingers in rubber gloves. Though I wouldn't call it rough. The threads seem okay. When I get back into the garage tonight I will snap a photo or two and refresh my analysis.

You guys rock. I've downloaded the manual and have a copy of the Clymer as well!