Vintage BMW Motorcycle Owners

Doing a service on my bike that includes removing the oil pan. Amongst a bunch or stuff I recently ordered from Bench Mark was a new set of bolts and washers. The ones they sent me have a shaft that is 3/4 of an inch long and the ones currently on the bike are 5/8 long. When I thread the new ones on without the pan they bottom out on the threads at a point that appears to be too shallow to snug the pan and new gasket down. Richard and Vech at Bench Mark are the Yoda and OB1 of Vintage BMW knowledge and if they were open today I would call them and ask them this question - was I sent the wrong bolts?

Anyone out there know? I don’t want to wait until Monday to get the answer.

This site shows you need 12 bolts that are M6x15...which means they are 15mm long...that is slightly less than 5/8".

https://www.bmwclassicmotorcycles.com/p ... e-housing/

I don't think being too long is an issue on all the bolts. The holes are through holes as far as I can remember but some might actually thread into the engine case. This is the part number on Vech's site - 07119913463 bolt 6x1x16 - which is M6x16 with 1.0mm pitch. They also show part 07119913476 which seems to be M6x1x20...that's closer to 3/4" long...maybe that's what you were sent.

Just measured them. 15mm are what I have on the bike. 20mm is what they sent me. Thanks.

The 20mm bolts could be for those running the deeper sump.

I’d gladly buy any of the old hardware that you’re replacing. I’ve got a 56 missing most of the hardware.

M6 stainless bolts are pretty common. These should be available at your local full-service hardware, just take one with you to match up the length.

My two cents on this: All those bolts being tightened into aluminum over and over again is bound to strip some threads sooner or later, even using the 'just barely tightened' torque recommendation.
When I rebuilt my engine this winter I replaced all the bolts with stainless studs (Permatex thread sealant on the through holes) and now use stainless acorn nuts to hold the pan in place.
I know it isn't correct, but it looks good and it'll make me a lot less hesitant to remove the pan going forward.
If you have to replace all your bolts again anyway, it's something to consider.
-Jon

Jon, Nice idea with the studs. As you stated, the oil bolts don’t need very much torque. I recommend using a 1/4” drive short ratchet and only make them snug. Keep the 9” long 3/8” drive ratchet away from them! The oil pan gasket will compress a little after some time, then re-snug them.