Front main bearing replacement on a 1979 R100T

[dfalatko]

I am replacing the front main bearing on a 1979 R100T. There is a retaining pin used to secure the bearing, but I cannot find a part number from standard diagrams to get a new one. Does anyone know a part number and/or where to get a new one?

 

[20774]

Can't say as I've heard of pins holding bearings in. Is it possible you're referring to a woodruff key?

https://www.realoem.com/bmw/enUS/showparts?id=0393-USA-03-1979-2474-BMW-R_100_T&diagId=11_1719

 

[stevenrankin]

Looking at the microfiche I see a dowel pin part number. Is this what you mean? St.

06​

07 11 9 942 050​

DOWEL PIN - 4X10​

 

[GTRider]

As Steve pointed out, it’s number 6 in this diagram (ignore pricing, which never gets updated):

https://www.realoem.com/bmw/enUS/showparts?id=0399-USA-03-1979-2474-BMW-R_100_RT&diagId=11_1706

Fitting the pin and cutting the recess in the bearing are fiddly, the factory service manual is useful here. And a good peening of the bearing carrier to prevent the pin from backing out and showing up in the oil pan…

Best,
DeVern

 

[dfalatko]

Thanks everyone, I think that is it, the size seems correct. I was bit thrown off since then bearing is in a different diagram. I appreciate the help!

 

[Lendog]

Can't say as I've heard of pins holding bearings in. Is it possible you're referring to a woodruff key?

https://www.realoem.com/bmw/enUS/showparts?id=0393-USA-03-1979-2474-BMW-R_100_T&diagId=11_1719

they are round maybe 4mm diameter,

 

[AntonLargiader]

Some mechanics now use a setscrew instead. I do.

 

[drost]

Anton,
Please explain the set screw method.

 

[AntonLargiader]

The factory method inserts a pin into the bearing carrier to lock the bearing in place and then the aluminum around the hole in the carrier is staked down with a square broach to hold the pin in place. This did not always work. In the mid-'80s production a number of pins came out. Also, the staked-down metal is now loose and other metal needs to be staked down during a bearing replacement.

An alternative is to tap the hole for [I think] M4 and grind a screw to match, both in length and in having a tip that engages the hole in the bearing. Thats what I do. I make it so that the head of the screw bottoms out on the carrier when the tip is just below the inner surface of the bearing. I machine the smooth round tip by screwing it into a nut and then mounting that in the lathe.

I use an allen-head screw, probably having 10mm of threaded length, and then I modify from there.

 

[drost]

Thank you Anton. I will probably never have to do that, but now I know what to do if I have to.