Hello Everybody!
Haven't had much time to enjoy the Beemer this past year, between the convid and an elderly mother needing help 1500miles away, things just started to settle in late March. My plan is my 7th Saddle Sore 1000 on my 1981 R100RT and my 5th year Summer Solstice which started in 2017.
Seems every year there is a major Fix the bike needs. In 2017 I redid the heads and installing a 4gal auxiliary fuel cell, 2018 more carburetor work and LED lights upgrade, 2019 well not much just cleaned up some wiring and a voltage regulator I was too busy getting a new to me 1987 Honda GL1200A ready for 8K ride around the USA, 2020 just tires and fluids and a sidecar took my time, but 2021 has been a big pre-ride preparation.
The final drive needed work.
So back on May 4th I began disassembly of the final drive, it was having much leakage in the rear tire. Also the drive shaft housing is “loosing” lubricant but it’s not leaking out. I believe both the drive output seal and the drive input are both leaking. While I’m at it I’ll fix the gear oil level check bolt which is epoxied in place.
On May 20th, I finally completed the final drive rebuild, really just a reseal in which the outboard needle bearing of the ring gear needed replacement. It's really only a couple hour or day job but waiting on parts out here in the boonies adds a lot of time if you don't get everything at once
- This unit has be opened before. There is thread lock on the cover plate bolts. There is no gasket on the cover plate, a gasket maker liquid that only hardens in the absence of air was used.
- I needed a couple specialized BMW tools. I bought these tools and a re-sealing kit from Boxer2Valve. The owner William runs a youtube channel with great demo’s of this type work.
- A 4 tang large socket that will grip the notches in the Pinion seal holder
- A tool to hold the pinion to drive shaft gear while removing the bolt holding the gear in place is loosened.
- Next was a nice to have not “Needed” tool that is a flat plate that bolts to the 4 studs on the final drive to drive shaft tube face which lets my big bench vise hold onto the final drive without damage.
- The drive spline the connects the the tire is about 20% worn away, SnowBum a west coast Airhead Guru says is replacement time at 66% worn. So just a cleaning and lubricate with copper based anti-seize.
- Ring & Pinion gears look good, no chips or other strange wear.
- While removing the outboard needle bearing I screwed up and did not get the case hot enough. I damaged the shell. I new bearing and race came from MaxBMW. Another C-note up in flames.
- On assembly checked the backlash and gear mating. Both looked good without using the cover gasket. I used Permatex Anaerobic Gasket Liquid for the cover.
- Used Permatex High Strength Thread sealant 56521 on the Pinion input seal holder. Filled the Final drive with Valvoline SynPower Synthetic Gear Oil 75W-90. Straight 90W is recommended but is NLA.
- And since the rear tire was off a new Avon Roadriders. The old one still has tread at a bit over 9k miles but I like more tread before an IBA ride.
Hoping to get a real road test this week, just time enough for a ride around the parking area today. Crossed fingers everything is right, the magical Summer Solstice is coming up quickly.
Edward
My final drive output seal (78 R100RS) started leaking last fall and spitting oil onto the rear wheel. That was my first trip into that thing! I did not need any special tools for that seal only, but I did use William’s aluminum can seal protector idea. Worked great. All is well now. My drive spline was redone sometime back in the 90’s, and seems to be doing OK with about 1/3 gone.
I've done auto differentials so my first visit to the Final Drive wasn't stressful. Just my first with these exotic alloys 🙂 Yes if only doing the output seal, no "special" tools, but my pinion input seal was leaking too much to ignore. Also the lack of a gasket made ordering Anaerobic Gasket Liquid which took a few days to get. I've never used this stuff before so fingers crossed.
I used a fizzy water can and lucky my wife drinks the stuff, I'm strictly a water and coffee guy!
I've been binge watching William's channel so I pay back for his content buying from his shop.
Sunny cool day, time to check this ride out!
What I like about anaerobic sealants is that you are not “under the gun” to get things assembled and torqued. I dislike being rushed because time is ticking on the goop (and I’m slow!). It is curious that your cover had no paper gasket, but, given the zero clearance metal-metal situation, I’d say the anaerobic sealant was the way to go.
I’m hoping my input seal will hang in there until I need new drive splines again. Then I can just get the entire final drive rebuilt .... again.
Hope your test ride goes well!
YEAH, just got back from a 23mile ride and all seems well. I took my remote IR thermometer and measured the surface temperature several times in several locations on the FD. 95F at the bottom, 87F at the top, 93F at the top pinion to axel tube junction was max until some heat soak when I got home. I did several sprints to 75mph, but mostly in the 45-60mph range. I've never measured the final drive temperatures before but those numbers seem fine. So next is my real preSS test ride.
My typical preSS test ride is a round trip to Medway ME up I95 almost exactly 200miles total. I get all systems up and do a practice gas and go, fill the aux tank, run Spotwalla, hydration, snacks, etc.
I've seen conflicting data on whether the 1981 cover has a traditional gasket or a liquid gasket. I used the liquid since that's how it came apart and I didn't want to have to re-shim. The backlash was just in spec without a gasket.
Give a mouse a Cookie! I started by wanting only to reseal the right petcock. Then since the fuel tank was off I decided to check the volt drops to find why my voltmeter reads 1 volt low, so cleaning starter relay, remove and clean the ignition SW, clean the fuse holder and... 1/4Volt drop most of which is in the meter. No meter adjustment so I'll live with the 1/4V. So heck since I decided to put internal fuel screens on it will be a few days, let's clean up the diode board connectors and grounds. Oh and why not put in a dedicated ground from the upper left board mount to the battery neg. Well, really the alternator to diodes wire is looking tired, new wires are whats needed. Oh and really my rubber mounts for the diode board are fine but metal would be so much better! And since the front cover is off I really should........
HOLY COW IT'S JUNE FIRST!!!!!
The good news is the both petcocks are now smooth operators 🙂
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