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1991R100 GSPD Drive Train Problem

9515
 9515
(@9515)
New Member

I hope every one is having a great thanks giving today and you don't burn the turkey! 

 

My 91GSPD has a drive train problem I can not determine if it is related to drive shaft  or real differential axle. The transmission has been rebuilt by Ted Porter and when i put in the clutch the issue of clunking or vibration continues so i dont think the transmission is the problem.

One Clue, a month ago when i would get to work in SF and go to my parking space i coast down hill on the ramp. Now i noticed a kind of vibration when i turned to the left to get to the motorcycle parking (motor not in gear).   Later i went to sacramento to visit a friend an on the way i noticed some slop between gear changes when i re engaged.  Next on the way home that day i was just getting on to the freeway and it sounded like i was dragging something like a crushed can on the pavement.  I pulled over and  looked nothing was caught underneath.  Then when i restarted where was clunking sounds and i knew some problem existed that would prevent my journey home.  I returned to my friend's house who had a trailer to tow bikes and he returned me and the bike home.  I just checked the Clymer BMW manual and could not see any instructions for discovering whether my problem lays with the drive line or rear diff axle. I would like to know which is was or what to check to see which is the problem part.  I suspect the rear dif axle as it was in turning i first noticed the problem. any suggestions how to proceed appreciated. Swanny

Quote
Topic starter Posted : 11/26/2020 13:01
Scot Marburger
(@8166)
Member Moderator

What tires are you running? I ask because the vibration you describe while turning could be from lugs on the side of the tire hitting the pavement. You don't feel them as much when the bike is upright because they've worn to even heights.

Where is the scraping sound coming from? Put the bike on the center stand and in neutral with the engine off spin the back wheel while you listen. Try putting the steel end of a screwdriver on the transmission housing and holding the plastic handle to your ear while you spin the wheel. That will help you isolate the sound to the area around the tip of the screwdriver. Work your way down the swing arm and probe the rear hub, too.

If I had to guess, you have a broken spring on the brake pads in the rear hub, and you're hearing the spring drag on the hub. But you need to carefully probe while listening to get a better direction for your search BEFORE you start taking things apart.

ReplyQuote
Posted : 11/26/2020 13:54
Richard Whatley
(@wobbly)
Member Moderator

I take it this is a single-sided rear end. Almost all the load is carried by a huge 6.5" ball bearing. The health of that bearing also determines the fit of the much smaller RS tapered roller bearing. With any combination of: age, mileage and/or lack of maintenance, that big bearing can/will go bad. The last one I replaced was an 1988 RS with 80K road-only miles.

In the beginning the wheel shows about 1/16" of play at the rear wheel rim. Sort of a clunk-clunk when the wheel is push-pulled from the side. When the bearing gives up, the balls pop out and then lodge between the pinion and ring gear, which instantly stops ALL forward motion for the entire bike... no matter how fast you are going at the time. 

A pal's Oilhead GS gave up at high speed in the "fast lane" on the interstate in Atlanta. That left a 30 foot black mark as he wrestled it to the center wall emergency lane. Then he spent 2 hours sitting atop the dividing wall with 6 lanes of traffic on each side, waiting on the local BMW rescue truck to arrive. He had to buy an entire final drive assembly.

All the best.

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 11/26/2020 16:29
9515
 9515
(@9515)
New Member

The tires Metzeler dual sport type so not aggressive tread.  No slop when moving the wheel side to side.  I will be getting to the GS in a couple of weeks thanks for the ideas. I am hearing noise in the drive line area when i move the wheel by hand while on the center stand.  

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Topic starter Posted : 11/28/2020 08:03
9515
 9515
(@9515)
New Member

ok I found the problem was a toast ujoint in the non repairable drive line.  I decided to go with the Ted Porter Beemer Shop's upgraded repairable Drive line offering plus the upgraded bottom Pivot bolts that include Zerk fitting so you can lube this.  I dropped the drive train off at AirHead Adventures in  Redwood City CA with the new driveline and pivots  For Greg to do the the installation there.  By the way what a cool place! Greg is a Supporter of this Club has the Airmail club mag available and it is like a museum to see all the bikes he is restoring there.  So i am picking up the completed up dated drive train today.  It turns out that the 1990's BMW R100GS is noted to be prone to have drive line failure if driven two up loaded off pavement like mine was. Note there is a facebook group for the BMW R100GS owners only and i asked there for feed back on the new Drive line that Ted Porter offers and got very positive feed back from 5 people who had used it; so that was reassuring as it is $700+ with the upgraded Pivots and tax.  i would have posted a picture but the tool to add photo would not accept my photo which by the way is less than 10MB

ReplyQuote
Topic starter Posted : 04/15/2021 10:14
Richard Whatley
(@wobbly)
Member Moderator
Posted by: @9515

I would have posted a picture but the tool to add photo would not accept my photo which by the way is less than 10MB

Photos are always best hosted offsite. That makes it simple and easy, with no limitations.

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 05/04/2021 13:08
Scot Marburger
(@8166)
Member Moderator
Posted by: @9515

i would have posted a picture but the tool to add photo would not accept my photo which by the way is less than 10MB

10 megs is an absurdly large size for a photo being viewed online. Use an image editing app and reduce the size to something under 500 kb. On a phone you can't tell the difference between a 70 kb photo and a 1Mb photo. I usually shoot for something around 200 kb, unless it's something I want people to be able to zoom in on, and even then, never post anything over 500 kb.

Glad you found your problem. Usually the u-joints get toasted when the rubber between the inner shaft and outer shell lets the two u-joints rotate and go out of phase. I've been running the Emerald Island drive shaft for many years with zero issues. Just bought another one for an R100R.

ReplyQuote
Posted : 05/05/2021 17:31

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