Boxerworks.com

'84 R100

I'm reading my books on the procedure to tightening the swing arm. There seems to be a requirement to preload the pins then back off and re tighten them. This is done before the swing arm nuts are torqued down. My books vague, and are not giving me the goods or torque specs on this procedure. Got any?

Snowbum's website has the info.

Kurt in S.A.

My factory book on the R90 says after you get the swingarm gap equal on both sides and you set one side and then bring the other in till it hits, apply 1/8 turn bias so there is no play. Guess you want it free, with no play whats so ever, with a bit of preload.

Finally torquing the nut will add preload. How much? Enough to consider.
I wobble the wheel and feel the play. Back off the pivot pin and wobble the wheel as you retighten the pin. You will feel the play reduce to zero at a specific point.
I torque my nut (just one side as jaggarra says) at zero play, or just the weensiest bit of play.
The nut should have a lot of torque. Ain't got my manual in front of me.

Thanx guys! Snowbum has a lot of it covered. For those who have made the modifications to the 12 point 27mm socket for the swing arm nuts; did you find it important to grind the face of the socket flat like this one?:

Swing arm pins: Center the swing arm then tighten pins to 15 ft/pd for pre load. Loosen off then tighten to 7.5 ft/pd. Nuts to 70-75 ft/pd.

Zombie Master wrote: ↑Thu Mar 16, 2017 3:41 am .... For those who have made the modifications to the 12 point 27mm socket for the swing arm nuts; did you find it important to grind the face of the socket flat like this one?:

Yes, otherwise the lead in on the socket significantly reduces the depth of engagement on what is a very thin locknut.

Although I have access to a lathe at work I was in a hurry so I spun the socket in an electric drill while attacking it with an angle grinder. The end result was at least as good as the socket in that pic.

I guess there is a lot of variation on the manufacture of the opening access to the srm lock nuts. I've ground off the OD of a socket and it seems to fit well but I guess I should try and flatten the face so I don't damage the nut. Looks like angle grinder with the socket in the vice.

Better to do it like Barryh.
With the socket in a vise and a hand held grinder it will be difficult to get a face that is flat and at 90 degrees. If it is off, only some of the socket will embrace the thin locknut.

If you can spin the socket and feed the face to your grinder it may come out flatter