Rear main seal question

[Bfr]

I'm in need of replacing the RMS on my r65 my local bmw dealer has no stock and it will probably be 4 odd weeks for them to get it in.
I know I can order it from a few different online sources but what about a std rotary double lip seal?
I know the genuine bmw item has the Teflon seal lip bit I çant see why a std rotary seal cannot be used?
Anybody with greater knowledge on these know why?

Thanks in advance

[pxc433]

Get the original right part. I think it has a tough life there.

BMW made a number of improvements over the years to that seal to improve reliability. They succeeded in this; I had problems with different bikes continually leaking there, until a replacement was fitted under warranty in 1990. 26 years later that part is still in place and working.

If it were me, I'd replace with only the real thing. It's too much hassle to get in and replace.

[ME 109]

I've never read of anyone finding/using a substitute rms.
No doubt the id and od could be matched, but there is a lot more contact between seal and crank with the flared teflon seal, than there would be with a lip type seal.
I suspect a lip type seal would wear a groove in the crank due to the narrow contact area. The flared teflon seal can also wear a groove in the flywheel or guide ring, but with less consequence. imo

[SteveD]

Welcome. No choices here except what Jeff describes ^^ in the last post.

Buy the right parts if you want it done right and it'll last another 250K kms.

For NZ, Motobins or Motorworks will be half the cost of the bits when compared to Munich in Perth. Munich will get them to you 5 times faster though.

[Bfr]

Cool as

Cheers for the advise it's always worth the question the day i stop asking questions is the day I end up 6 feet under.

[Zombie Master]

Cool as

Cheers for the advise it's always worth the question the day i stop asking questions is the day I end up 6 feet under.

But now we need answers. No free lunch!

[Bfr]

Went with the genuine item from Munic motorcycles.

Got the transmission out today and it looks like I should have ordered clutch friction disc as well.... gotta measure it but it's a nuts danglies from using the heads of the rivets as part of the friction material

Bugger

[ontic]

this what snowbum has to say on it

"New discs are ~6 mm thick. When worn below the official limit, 4.5 mm, they may slip. Slipping tends to show up first when using large amounts of power in top gear. If the rest of the clutch parts are in reasonable condition slippage may not occur until ~3.5 mm. No hard & fast rule here, due to wear (cupping on the pressure plate, wear on the diaphragm, friction material, etc."

my G/S friction disc was worn well into the rivet heads and measured 4.19mm thick but showed no sign of slipping yet.
Obviously replacement is the best thing but you might be able to put it off for a bit longer if you just want to get it back together?

if you copy and paste this into a new tab/page you can see what mine looked like
http://advrider.com/index.php?attachmen ... pg.517423/

[Bfr]

I know I'd probably get a few more k's outta it yet but I have destroyed flywheels in cars due to running on the heads of the rivets for the 150 odd it going to run to replace the friction plate and I'm in there may as well do it

[ontic]

Yeah sure, that certainly makes some good sense. I was only suggesting that as an option if you didn't want to deal with it yet and wanted to get a bit more life out of the parts.
Before deciding it might be worth checking your pressure plate and pressure ring- they are the only things that will like get hurt from wearing into the aluminium rivet heads (and I suspect the aluminium wouldn't hurt much anyway?). Are they already worn or cupped? If they are then there would probably be no harm in running the friction plate a bit longer till slipping actually starts and then replace the lot altogether.

Don't get me wrong though, myself I am replacing the whole clutch on my G/S- spring (which measures well out of tolerance), pressure plate and ring (which seem barely worn with some very slight cupping), and friction disc (worn past tolerance). I am replacing the lot because I am beefing up the engine and power a lot and from what I have read and been told it pays to replace the clutch as a whole unit, especially when upping the power.
If everything else in yours seems good, then yeah, why not replace just the friction disc while you are in there. I would.