1985 K100 Drive shaft splines

I trying NOT to hit the forum with more then one dumb idea every 2 weeks or so. I have a K100 that tugs an EML/GT2 side car. The PO had put on 20k miles and then I put another 10k more before I did a complete spline job. I found the FD/DS splines used up. I found a good used FD/DS. I put 10k more and did a FD/DS lube at the time of a tire change. I had used a moly60/lithium mixture and it wasn't doing well. I relubed with straight honda moly 60. Now 20K later and it is time for a tire change and I discover FD/DS splines are almost used up again. This means two FDs in 60K. I have found an other used FD set as Bruno's rebuild is far beyond my means. But!!! reading Bruno's website gave me an idea.

Is this a dumb idea? I am thinking about filling the DS with nonexpanding foam insulation. Then stuffing something like WalMart sacks into the space at the inside (forward ,beyond the splines) of the splines. fill the forward space that is left with grease and assemble. Now the only way that grease can get out is to work it's way rearward.

Harold in Kansas

I wouldn't do it. Do you want that stuff shifting around on you?

I have converted a few K-Bikes to run the driveshaft wet and they never wore out another set of splines. It's a fair bit of work, and they often leaked a bit, but on the whole, it seemed worth it.

Used, mismatched machined parts will wear extremely quickly. Buy a few more and you will have reached the cost of a proper rebuild.

As for your idea, the mechanical forces will force the lube out from the machined surfaces, said mismatched surfaces trying to wear together to match. Grease will not stop that wear.

Lostboy's wet solution sounds good, but again, you will need matched (new) splines on each side.

I wonder about the rubber damper in the driveshaft. Will the oil damage it?

Bob; I am using good used FD/DS pairs from the same bikes. They are matched.

Lostboy; Wet DS sounds like the /2 kind of thing. Do you have a reference that I can goto to see how it is done. This is an EML swing arm so I would hesitate to modifiy it. If I screwed it up, chances of replaceing it are slim to non.

Thanks for the inputs. Any other opinions are welcome. Harold in Kansas

[QUOTE=roncooper;750661]I wonder about the rubber damper in the driveshaft. Will the oil damage it?[/QUOTE]

One of the top mechanics (he's now retired) at Bobs' BMW ran his K75 this way for around 300,000 miles. No problem with the rubber damper. And he had no problem with the splines.

[QUOTE=hhshort;750677]Bob; I am using good used FD/DS pairs from the same bikes. They are matched.

Lostboy; Wet DS sounds like the /2 kind of thing. Do you have a reference that I can goto to see how it is done. This is an EML swing arm so I would hesitate to modifiy it. If I screwed it up, chances of replaceing it are slim to non.

Thanks for the inputs. Any other opinions are welcome. Harold in Kansas[/QUOTE]

I used to work at Bobs. The man who ran a K75 all those miles was Paul Mihalka, who is not offiially a mechanic; he was the sales manager there-he's just brilliant.

We had a local machinist mill, drill and tap the rear drive for 10mm plugs near the shock mount, so there's no risk to the EML swingarm.

Thank You LostBoy. That is just the kind of information I needed. I have the misfortune of several used up FDs on my shelf so I have one to practice on. Just measured and there is 13mm of room so now I need to find the little plug. I'm guessing the fill spec would be about like to /2. 250cc of EP 90.

We used the drain plug from a "K" water pump, P/N 07119919112 and used 100 cc of oil. Any more ran out the driveshaft boot.

Had 3 K100 RT 85,86,88 put over 328,000mi total and never had a fd fail and the fd at time of sale were still in very good shape.
The secret was told to me by a very good BMW mech in CA. He had a customer that was an engineer for an oil company. He was tasked to perform test to find a lube that would withstand the pressures, condensation and ability to stick to surface and still lube. This was in the 1980's. It is Permatex anti-seize lubercant with the # 133k on container. This Mech used BMW lube till warrenty was up then used this lube from then on. I relubed my final drive splines and forward splines each year 20,000. The last 3yrs I pulled a pop up tent trailer all over the US and finished with 138,000 0n the bike and splines were still good.
Had to belive but true. I still have a 1985 FD that I kept as spare but never needed.

Wow , what a simple fix to permanently cure a design weak point on an otherwise bulletproof machine . Now why didn't BMW do that ?

I would assume that the mating surface between the FD assembly and drive shaft tube needs to be sealed with permatex ?

Also , does a slinger need to added somewhere toward the transmission end of the drive shaft to keep lube oil from migrating its way up toward the transmission and out the rubber boot ?

Todd

I'm not sure I would call it a weak point under normal conditions. My other K100 is a 2 wheel bike that has 120k miles, has pulled a luggage trailer, a popup and is normally 2 up. The splines are as near to perfect as they can be. They get serviced every time a new tire was installed. The bike in question is a sidecar tug with car wheels and car tires. The car tires last twice as long as a bike tire and it is not as easy to pull the FD. The PO had neglected the service and miles piled up faster then I expected and I guess I had neglected as well. To be sure I will be inspecting the splines within 10k of the modification.

I'm not going to worry about oil migration. I wasn't an issue with the /2s.

As for sealing. the 2 surfaces are very smooth. It really would not take much. Any suggestions. Harold in Kansas

[QUOTE=hhshort;751978]I'm not sure I would call it a weak point under normal conditions. My other K100 is a 2 wheel bike that has 120k miles, has pulled a luggage trailer, a popup and is normally 2 up. The splines are as near to perfect as they can be. They get serviced every time a new tire was installed. The bike in question is a sidecar tug with car wheels and car tires. The car tires last twice as long as a bike tire and it is not as easy to pull the FD. The PO had neglected the service and miles piled up faster then I expected and I guess I had neglected as well. To be sure I will be inspecting the splines within 10k of the modification.

I'm not going to worry about oil migration. I wasn't an issue with the /2s.

As for sealing. the 2 surfaces are very smooth. It really would not take much. Any suggestions. Harold in Kansas[/QUOTE]

Permatex would work, I'd use ThreeBond to make removal easier when the time comes.
This oilbath sounds like a great idea, spline contact pressure would be the same as gear mesh contact pressure.

Thanks Bob. I was trying to remember what we used to seal cases on our 2 strokes and threebond was the stuff. Seals but doesn't occupy space. I will be using EP whatever laced with extra moly. I now have enough info and nerve to go after the mod before riding starts for real. I think we can now tie an knot in this thread. Thanks to all. Harold in Kansas

So, I ordered the plug referenced earlier in this post and
plan to take my FD to a machinist in the near future .

Question :

So, where best to locate the fill plug ?
Outboard of the shock mounting point ?
Or forward of the shock mounting point ?
Or ?

And I will fill with ~ 100cc ( 4 oz ) of 90-140w gear lube when done.

Todd