Boxerworks.com

Think there was a thread with similar title ? But, this is another nut to check every so often...

Finally got the 77 R100S ready for the road after sitting for quite a while...so off for the first road journey after sorting out a few things for sitting so long .....carbs, pushrod tube seals (no leaks but harder than nails and besides I wanted to check over top end) all the things for a bike sitting blah blah.....except....the nut

Ran beautifully but on way back home after about 100kms coming up slight hill close to home a funny loss of power...thought it might be clutch slip but nope...then heard a rumbling sound from the right side...hmmm...got to top of hill and shut down....started up, everytjhing sounded fine...engine purred, selected first gear and started down hill to the house...rumbling again...disengaged clutch...still there...hit kill switch, shifted to newtral and coasted home....rumbling still there...hmmm....thought it dropped a bungee off the side but nope.

In garage thought might be drive shaft bolts at tranny output as I'd taken out gear box to check for leaks and check clutch but all 4 were there nice and tight....I pulled the bike forward to get better lighting then heard sound again this time from the final drive...hmmm what the heck?


Pulled FD and low and behold the collar nut on the pinion shaft was real loose...could turn it with my fingers

Part #1 in this diagram

That nut usually on with some might torque but not this time...never thought of checking it either...
Pulled apart final drive for cursory inspection...nylon gasket (part #2) was disintegrated but seals looked good and bearings seemed in good order. Checked pinion and crown wheel gears too and they looked OK...maybe just got lucky. So off to local airhead mechanic and friend to check shimming and maybe new seals whkle got it apart and he knows more about them than I do....so check zee nutz....going to check those suckers every time I do tire change!!!

I am glad that you found it before it did real damage.

You plan to remove the final drive to check that nut for every rear tire change?

That nut doesn't come loose, or at least I have never seen, nor heard of it. The last person working on that seal left that nut loose.

You're right Duane...I got lucky...real lucky!

Took FD over to buddie's shop today. He also said he's seen only one loose like that in 35 years and it was due to someone not torquing it up properly as far as he could tell. Everything checked OK so just a reseal and new nylon shim washer and we'll see how it goes.

I got all repair orders for this machine from 1977 to 1994 when first owner sold it at 41,000kms so maybe check through them to see if any work done of FD and maybe explain why this nut loose. The 2nd PO gave me all the papers. He only put on about 5,000kms on it after he bought in 1994. Kind of makes me wonder if maybe FD was removed and worked on which might explain a loose nut? But these FD's are virtually bullet proof so maybe a wild goose chase...just curious. It'll be interesting if I found out anything. Kepp ya posted.

No I don't plan on checking this at every tire change but will anytime I have the FD off any bike!

The exact same thing happened to me on my R80RT (at 75 mph) a few years ago. It was pretty ugly. After giving Oak $175 to fix it, it leaked like there was a 1/4" hole in the bottom of the casting. So, I bought one off eBay for $200. It was junk. So, I paid $1162 for a brand new one. It was junk, too. It transferred oil forward into the shaft housing, then further forward into the tranny. So, they sent me another new one - no charge. Nice of 'em huh?

Yikes at 75mph...whoa

So did you just get the big rattle can effect? Would there be a possibility of locking up the rear drive...that would be exciting to say the least! Probably not lock up though...just freewheelin'?

I still can't figure out how this collar nut loosened off. PO gave me a stack of invoices/work orders which I went through and see nothing that would require the FD being removed. Hmmm....the sleuthing continues.

I've bought a few used FD's off IBMWR.org sight and they all turned out fine. Think the e-bay sellers really don't look at them that well. Right now I bolted on a known good FD (32/10) from a 78 /7 just to get it back on the road...interesting how far out of whack the speedo is vs the 33/11 that was on the 77 S. Hope to get it back next week after resealing and reshimming it and see what she goes like. Great bike...lots of umph in the 77 big valve/squish band hi-comp engine.