Featherbed rear engineplate mounts out of line...

Hi, I am making some changes to my Slimline Featherbed-Commando by instaling a Sportster electric starter (bad right knee after 35+ years of kicking British Iron)
Also fitting a Commando chaincase instead of the tin Dominator one and a reworked centrestand to clear the 2in 1 exhaust pipe.
Atm I am making new engine plates to be able to craft a 'cradle' for the Sportster starter and moving the tranny ± 4cm forward as the Commando distance is shorter compared to the Dominator distance betwee engine & box.
To my amazement I found the upper & (!) rear engine plate mounts on the frame out of line with the engine.
Engine crankcase is 84.2 mm (3 5/16 ") wide, upper rear mount is 83.5mm and bottom is 85.8mm wide.
With the old mild steel engine plates this was obviously never a problem, you simply sqeeze them.
Up to now (since 1988) I have been riding it with Dural plates but had 'trouble' with keeping the box in it's position until I made up two special spacers and milled them into the surface of the Dural to fix the top bolt box on it's spot
Forgot to mention that I run a Steve Maney belt + outrigger bearing. (engine sits upright in frame, as it should on a Norton...)
And yes, I once broke the outrigger, (to my surprise...)
Now I know ....
Anyway, did any of you find this on their Featherbed frames ??
I can change the mounts on the upper rear brigde piece as I can take it out, the bottom one is a different story.

Vincent

I had jigged up quite a few slimline frames as well as manufactured them and never experienced this.

The rear of the engine and the gearbox mounts widths obviously set the requirement for the frame mounts, and the gearbox and motor must be centralised. I'd use spacers if the frame mounts are too close together - it sounds like your frame is a replica.

Hi, frame is a original, bought in 1980 as a rolling chassis from a 650SS with papers, I doubt if there where made any reps of slimlines in those days.
As I was working on it with the engine still in situ , today I loosened all bolts that holds the motor, no chance.
For some odd reason the rear upper and lower mounts are out of line.
Frame is not not bend or molested in any way though, it's the most stable bike I have ever ridden, I can make my sandwiches on the tank while on the move.
Plan is now to grind down the lower left hand mount by 1.6mm on the outside (between mount and lower frame rail) by hand with a angle grinder.
Maybe I weld on some stiffening on the other side to make up for the loss in thickness.
At the upper mount I only need to put a washer in to solve it's undersize.

but first I sleep on it for a night. Thanks for your input. Vincent

After some thought I did not put a angle grinder to the frame but altered the plates.
(new) engine plates are 6mm thick, milled 1.9mm from the inside at the lower right hand point on the engine plate (re-measured the points, it was 1.9 instead of 1.6 out of line)
Added a washer of 0.7mm at the top mount.
Problem solved - I think-
Most likely cause: A on a mondaymornig in Februari 1962, someone at the factory moved the framejig and forgot to slam the wooden wedge under the right hand corner that was supposed to level the damm thing.
They found out after the 10 O'clock tea and put it right, but to late for my frame....

regards, Vincent

vincentgin said:

After some thought I did not put a angle grinder to the frame but altered the plates. (new) engine plates are 6mm thick, milled 1.9mm from the inside at the lower right hand point on the engine plate (re-measured the points, it was 1.9 instead of 1.6 out of line) Added a washer of 0.7mm at the top mount.
Problem solved - I think- Most likely cause: A on a mondaymornig in Februari 1962, someone at the factory moved the framejig and forgot to slam the wooden wedge under the right hand corner that was supposed to level the damm thing. They found out after the 10 O'clock tea and put it right, but to late for my frame....

Click to expand...

Sounds about right.