Transmission bolt length for 1961 R27

schrader7032 · Post by **schrader7032** » Thu Jul 02, 2009 8:30 pm

I'm not real sure but it looks like the studs are #2 in this picture:

http://www.realoem.com/bmw/showparts.do ... g=11&fg=10

The table indicates they're 30mm long. Aren't the studs fixed in the engine case and then the tranny is held in place by the four nuts and washers?

It would appear that all the studs are the same length.

How much of the sheared off bolt is still sticking out? Could you still get a grip on that plus some heat on the case to release the stud? My guess is that at least 5-6mm, maybe even 10mm has to be still inside the case. Seems like you could easily get away with going in that deep without fear of hurting the case.

Kurt in S.A.

ferguson7349 · Post by **ferguson7349** » Thu Jul 02, 2009 9:23 pm

Kurt, a million thanks for your input and research. The transmission bolts I'm referring to are four that mount the transmission to the underframe - not laterally to the engine. They run parallel to the ground. Seems like you have the resources, and perhaps you can zero in on that.

Kind regards,

Paul

schrader7032 · Post by **schrader7032** » Thu Jul 02, 2009 9:39 pm

Paul -

You got me there...I'm not really that familiar with the singles. I was thinking about the times I've removed the transmission on my twins and remember the "studs" that the tranny slides onto.

I'm not really visualizing an "underframe". Wasn't the R27 rubber mounted to the frame as compared to its predecessors?

I guess we'll have to wait for someone who knows or has one of these bikes.

Sorry...Kurt in S.A.

ferguson7349 · Post by **ferguson7349** » Thu Jul 02, 2009 9:45 pm

Kurt, as I recall (and I'm in the kitchen without the manual in front of me) the plate through which the four bolts pass is in turn attached to the rubber engine mounts. Right now when you kick over the starter lever the fact that one of the mounting bolts is sheared allows for a significant twist to the low end of the engine/tranny section which I suspect would be less if that 4th bolt were secured.

Concur, let's see what the rest of the gang comes up with. Thanks for jumping on this so quicly however!

Paul

schrader7032 · Post by **schrader7032** » Fri Jul 03, 2009 6:35 am

Paul -

This page shows the rubber mounts and bolts that hold them to a metal bar.

http://www.realoem.com/bmw/showparts.do ... g=23&fg=05

That metal bar mounts to the lower part of the tranny using the nut and washer #8 and 9. The stud in the tranny is shown but there's no part number associated with it. Actually, it looks like there's two studs per rubber mount.

The mystery continues...

Kurt in S.A.

ferguson7349 · Post by **ferguson7349** » Fri Jul 03, 2009 8:09 am

Very interesting - it makes it look like there's a stud sticking out of the transmission casing that #8 and 9 fasten on to, which makes for a really interesting situation. I'll check the remaining three "bolts" to see if they are really studs with washer and nut on each. May have to forget trying to make this fix.

Thanks for the additional research, Kurt!

Allan.Atherton · Post by **Allan.Atherton** » Fri Jul 03, 2009 8:28 am

I have just removed my transmission to replace the clutch, and here is a photo of the mounts:
http://www.flickr.com/photos/roundel/3683579979/

I can't imagine replacing a stud without removing the transmission.

I chose the rear approach to remove the transmission, pulling the swing arm back, rather than pulling the motor forward, because I didn't want to pull wiring out of the motor or risk scratching the frame. The rear approach is not obvious and must be described in detail or labor could be wasted.

I did not have complete instructions, and thought I could un-nut the bottom 4 studs. However, with all the 8 studs in place, they trap the transmission against being removed. To pull the transmission back off the motor, don't touch the bottom 4 studs. Leave the bars on the transmission and just unbolt the 2 rubber mounts.

Before realizing that, as I un-nutted the bottom 4 studs, I found the nut on one of studs was too tight (nylon locknut) and pulled the stud out. This caused oil to drain out, revealing that the studs penetrate the case.

If a stud is drilled out and tapped, shavings could get into the case. I would work from below with the case full of oil, and keep pouring in oil to flush the shavings out.

One of the rubber biscuits was partly split after 10 years and 8000 miles, so I ordered all four.

ferguson7349 · Post by **ferguson7349** » Fri Jul 03, 2009 8:36 am

Allan, that was right on target! Thanks so much; particularly for the great photo! That, coupled with your discussion makes the situation strikingly clear. Since I don't put on more than 300 years a year on this bike I'm thinking I'll go with the three that are tightly secured and merely make full disclosure if I sell the bike eventually - something I wish the previous seller had done with me.

Kurt, pretty cool summing up, eh?

Paul

schrader7032 · Post by **schrader7032** » Fri Jul 03, 2009 9:13 am

Kurt, pretty cool summing up, eh?

Paul -

Sure is...it's nice to have some diversity in the members. Allan has quite a collection of pictures which is very helpful to see what's going on.

I don't own a single, but I'm hoping to find an R25/2 made the year of my birth. I'd like to have a vehicle as old as I am...but hopefully in better shape!

Kurt in S.A.

VBMWMO · Post by **VBMWMO** » Mon Feb 15, 2010 2:52 pm

Purchased my 1961 R27 on E-bay over a year ago and recently became aware that one of the four transmission bolts was sheared off. The local Kawasaki dealer has the bike up on his lift and has ordered a diamond tipped drill to make a hole for an extractor in what appears to be super hardened steel but tells me he is unwilling to proceed until he knows what the length of the bolt is for fear of penetrating the transmission casing. I suggested taking out the opposite bolt and measuring it and he states there's no guarantee they would be the same length. Does anyone have the drawings or other specifications that would give the lengths of the four bolts. At the moment I forget which is the sheared one but can easily find out if they truly are of differing lengths, which I somewhat doubt.