Gear Stripped???

[Crossrodes]

Boy does it ever end with this bike ('79 R65)!

In the last few days I have noticed when out for rides that under heavy acceleration I feel this light skipping/clunking in the seat of my pants.  It feels like it is coming from the rear but who knows.  On Wednesday night I was following a friend...riding somewhat aggressively when I felt the clunk/skip for about the third time.  I slowed down for a couple of minutes and the clunk disappeared.  I came home and drained the final drive and shaft oil to check the magnetic plugs...but there was nothing unusual there..just a few filings on the final drive plug which I would think is normal.

Today I went out again for a 250km ride and it started again but only under heavy acceleration.  I'm guessing that I have a worn cog somewhere; but where (transmission/shaft/final drive)?  Is there any particular component that is prone to failure/wear that I should check first.

I planed on pulling the drive train apart this winter but I'm thinking maybe I should start now.

Thoughts???

[Bob_Roller]

There's a spring loaded 'ball and socket' type assembly in the drive shaft, called a 'cush drive' .

May be a suspect assembly .

[Crossrodes]

Bob would that be the thrust adapter in this diagram?
http://www.realoem.com/bmw/showparts.do?model=0353&mospid=47850&btnr=26_0112&hg=26&fg=05

[Bob_Roller]

That's the beast .

[plc]

Oh so is that why my bike knocks on deceleration sometimes?

Is it essential to fix it soon? My bike has done it since I bought it 18 months ago.

Paul

[Crossrodes]

Paul, mine doesn't happen on deceleration, it happens on acceleration.  My experience with cars would say that you may have a worn rod bearing...but who know what the BMW is doing.  

Others may chime in.

[nhmaf]

Put bike up on centerstand, gearbox in neutral, engine off.  Lift back end of bike so the rear wheel is off the ground/front wheel on the ground (if you have one of those "old man" ride-off stands, stick a board underneath it to gain necessary ground clearance).   I place a jack stand in front of the rear tire and under the frame so that it supports the rear of the bike at the lower cross member of the bike frame.   Slowly turn rear wheel forwards and backwards, observing for "clunks" or strange sounds as the wheel turns.   Go through several rotations in each direction, paying careful attention to the points soon after you have reversed the direction of rotation.

Then, put the transmission into a gear (any will do). rotate rear wheel as before, though you should only be able to move it through a couple inches or less of travel before you feel the resistance of the engine.    If you can move the wheel more than a couple inches, or more in one direction than the other, or you hear/feel strange "clunks" while doing this,  report back here to us, and we may be able to help narrow things down further.

[steve hawkins]

And what are your swing arm bearings like as well.

Here in the UK we have yearly inspections that will not allow you to ride with shot wheel, head or swing arm bearings.  

If they are really suspect then you will know all about it, as your handling will also be suspect.

Not sure if you have a yearly inspection in the USA.  It is a good thing as it keeps the really worn out bikes off the road.  But the tests are always getting tighter.

Otherwise you have to check for 'slack' in your drive train as suggested by nhmaf.  A certain amount of slack can be lived with.  But if anything is about to let go, eg U/J or drive shaft bolts, etc, then you had better deal with them.  but it does mean a serious strip down to check.  Piece of mind, though, is invaluable.

Steve H

[nhmaf]

As far as I know, every state has a safety inspection, though some states are definitely more thorough about it than others.   In my state (NH), all bikes are inspected in the month of June, and things like worn tires, bent rims, non-functioning lights of any kind, non-working horn, no rearview mirror, leaking suspension or seriously leaking drivetrain, wornout brakes/leaking m/c, or bad bearings in wheels or steering head will all require correction before one can get an inspection sticker.   Some states require  tailpipe emissions testing and/or hooking up to the diagnostic computer (if bike is so equipped with OBD), but most states don't have this requirement for motorcycles as old as the R65

[Bob_Roller]

No inspections here in Arizona, but you are required to get an annual exhaust emissions test if you reside in the Phoenix or Tucson metro areas, unless you have collector insurance, and have historic vehicle plate on the bike, then the bike is exempt from this requirement .

[montmil]

In Texas, motorcycles older than twenty-five years can carry a Texas Antique Motorcycle plate that's $51.00 for five years. Plated as such, no safety inspection sticker required. Supposed to limit the bike to parades, club outings, riding to repair shop, blah blah blah. No one gets stopped. Never. Ever. "Honest officer, I'm riding it to warm the oil prior to a change. Really."

I have one plate that I switch between which ever R65 I'm riding that day. Now, y'all don't rat me out, OK?

Monte