Hi all,
Spent the day divorcing my sidecar from the K, dropping the sub frame and removing the trans for a spline lube. Found heavy oil soiling in the bell housing so Im assuming I have a leaky main seal - but that can wait a few days.

The side car subframe shares the OEM engine/frame mounts at the front and uses an 8mm 10mm allen head bolt (not the fancy cap loc bolt).

This bolt (LH side) spins easily but will neither tighten nor back out. It feels like its stripped or sheared) but it wont extract with a magnet or with me pulling on the (otherwise unfastened) subframe.

Does anyone know if the engine case hole is directly threaded or is there a threaded interference fit bush inside the hole that may have come loose or possibly even, does it sound like a failed helicoil?

Hi,

Are they the 10mm, not 8mm bolts numbered #1 and #2 in this diagram? If so I believe that the engine block mount tabs have a nut on the opoosite and inside of the bracket to accept these bolts. I used these mount points for my Flexit sidecar.

https://www.realoem.com/bmw/enUS/showparts?id=0513-USA-02-1987-K589-BMW-K_100_RS_83_0502,0503,0513_&diagId=46_1268

Try to pry under the bolt head or your captured bracket at the same time you are un-threading. Sometimes this will be enough to get off of the thread stripped portion of the bolt.

Glenn

Thanks Glenn, now you have confirmed the case is threaded I’ll attack it accordingly. I’m guessing the additional sidecar stress has killed it, although I’m surprised it hasn’t shown up in handling/vibration.
Back on it tomorrow, Cheers, Stu

Hi!

Check my edit ;-) I think this is a bolt and nut attachment. I have many pictures of my Flexit bracket building, checked them and think their are inboard nuts for both of these frame to motor front mount points.

Glenn

yes bolt and nut attachment

good advice glen

Thanks Guys, After a day of hassling with the sidecar and transmission I probably wasn’t seeing straight yesterday. Back on it today and get that clutch out.
Cheers.

Excellent!

Hmmm, interesting.
This may be one of those cross over year issue things as Ive certainly got other bits on an early 85 RT that aren’t the same as the years around it.
The RH mount is definitely into a blind hole that runs under two longitudinal ribs on the top of the crank case. I used this set up as my reference as the LH side is buried under plumbing and TB mechanism.
The LH bolt runs through a crankcase tab to a nut (which is completely hidden from view).
I’ve struggled to find pictures or descriptions of this set up.
Thanks for your help.

forgot I took this pic ...hope it helps

Thanks Charlie
That looks exactly as I have on the LH (valve) side. Your pic looks like the RH side is either internally threaded on the crankcase tab or maybe could hold a captive nut between the two ribs. Either way I can tighten or loosen that one using the bolt head only but looks like I’m going to have dismount (at least) the injector rail to get at the LH nut.
Oh well. Certainly better than helicoil.
Stu

there is usually a little wiggle room under the radiator core , so you should be able to place the nut through there , if you have the radiator cover off ?

charlie99 wrote:there is usually a little wiggle room under the radiator core , so you should be able to place the nut through there , if you have the radiator cover off ?

Great tip Charlie! The nut isn’t even off so I’ll see if I can get a wrench on it via the rad.
Stu

Good picture from Charlie,

If the left hand mount on your motor is tapped and stripped, I would tap it out from 10mm to a 12mm rather than using an insert. With the sloped gusset on the motor mount bracket, you can probably not get a nut to sit squarely.

Glenn

hi glen, I don't think a 12mm bolt will fit through the frame ,  some later frames have rubber isolation on the front mounts and a 10mm ferule through the rubber.

 just a heads up

Yeah, that wouldn't work! Good call.

Glenn

glennpm wrote: With the sloped gusset on the motor mount bracket, you can probably not get a nut to sit squarely.

File the sides off the nut, as in - been there, done that

Hi,

I've done that too for smaller angles, like on a slope of structural steel. I just had an idea though that could work, use a threaded coupler.

8MM threaded coupler

As the LH side mount is a thru hole taking a 10mm bolt and nut but a bit longer than the factory job to accomodate the subframe I have sacrificed a cheap ring/open end spanner for this purpose. On loan at moment otherwise I would post a photo. From memory I think it was 17mm and I thinned it down with the grinder and tweaked the angle slightly until it fits easily. To put it back just silicon the nut in the spanner and hold it in position and turn the bolt until tight, just don't use too much silicone as you only want to hold the nut until you get a couple of threads started.

Regarding holding the nut in the wrench, I use blue masking tape, a loop around the wrench and push the tape over the nut to hold in place. The tape is easy to remove once you have the engagement started. For obscure locations, I sometimes wrap a loop of tape, sticky side out, to hold the nut on my finger tip or screwdriver until I can get it started.

Glenn

Finally got back to the front end and following advice I have been able to wriggle the open end of a 17mm under the radiator and onto the nut. Hopefully that will give enough of a hold when it comes to torque time.
Thanks all.

Good!