solo seat

[Tony Smith]

Hard to argue with that.

But what was the difference? You see when we set about putting the r80 engine in place of the blown r65 engine in 1987 I compared, to the greatest extent possible, the frame dimensions between the R100 and the R65 and found them to be the same.
 
Would BMW give a different frame number because a brace was moved or a bracket in a different position - of course they would. Just because a frame has a different part number does not mean that has to vary in any more than one very small detail.

The total lack of difference in dimensions  I found was what gave confidence to buy a low mile R80 engine and fit it.

So my question would be, what is the difference between the frames?

[Rob Valdez 79 R65]

So my question would be, what is the difference between the frames?

Definitely all of the miscellaneous tabs for electrics, but also probably the sidestand mount, as the sidestand was unique to the 248, as well.

I don't know about overall frame dimensions, but engine mounts have been identical for a long, Long time.  As you probably know, you could put a 1984 engine in a 1955 (possibly earlier) frame.  Slides right in.

[Tony Smith]

 As you probably know, you could put a 1984 engine in a 1955 (possibly earlier) frame.  Slides right in.

I didn't know that, I've assumed that "current" airhead engines would only interchange with about /5 on. Thank you for that.
 
I am however going to run a tape measure over the wife's r65/80 and my own r65 as visually the sidestand and center stand on mine are very different.

[Tony Smith]

My cure was to build up and thicken the end stops with weld and then grind back gradually testing the stand for a correct fit and angle. The original ends are a laminated construction which I think is is one reason why they wear. After welding they are much stronger. While I was about it although my tubes were not worn through they were getting thin so as a preventative measure strips of stainless steel were welded on carefully and dressed with an angle grinder so as to be hardly visible. Stainless was used because it will wear much better than mild steel and also because the metal in contact with the ground will not rust. I believe the modified stand will be more durable than new.      
 

Unfortunately for me "she" was looking over my shoulder when I read your post ("she" was really only interested in seeing the photos of her bike - I was remonstrated with for not waiting until it was cleaned). I am now under orders to modify her centre-stand in a similar fashion.
 
I am lazier than you and will simply use stainless steel rods and build up some weld and then grind back - like you the goal will be to greatly reduce the over-centre angle.

[tvrla]

The frame geometry is the same with the R65 and the bigger bikes. But the differences would be the muffler mounts and possibly other odd bits - like the electrics on the right side of the backbone.

I like that idea of using stainless to build up the center stand. Clever!

[RSMike]

Sorry for not replying sooner, I have been busy with work and have neglected the forum for a few months now. I fitted a  /7 Solo Seat 91921B from Motobins with no mods to my 1980 R65:



more details here: http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1347557745/0#0

having said "no mods", I'll qualify that by saying I did have to make some slight mods earlier to accommodate a /7 dual seat and I don't know if these would have been needed for the solo seat, or not, more details on that here:
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1309703763/0#0

and on seat stencil kit, here:
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1367439822/0#0