Frame replacement

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dimitri

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Apr 4, 2013
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Hi everybody,

After a crash with bent frame a few months ago, i have most parts ready now to swap the frame of my 74 roadster.

I did swap a lot of motorcycle engines in the past, but no experience with commando's (or Isolastics adjustment) yet.
Never thought of it, but now that i want to start with it, it seems like a big job to get it back on it's wheels. Am i correct that everything has to be removed to be able to get the engine/gearbox out? Primary, cradle, swing arm, ...? Or is there a specific (faster) way for this.

I am not afraid of the work, but need my garage space. So when i start, the bike needs to be on rubber again as soon as possible.

thanks in advance!

Dimitri
 
A long time ago, maybe 1974, a friend and me replaced a Commando frame in a day, in the street. I seem to remember we took the swinging arm off but left the engine, gearbox and primary drive intact. If you're in a hurry you could probably leave the rear wheel mounted in swinging arm and even front wheel/mudguard mounted in forks. Good luck.

Ian
 
i was hoping that would work. I guess i would need to protect the new frame very good not to chip the paint.

Or maybe better... attach the engine/gearbox on a stand, and manoever the frame over it.

The front fork is not really a problem. As long as i can push the bike out of the way i am happy already.
 
I seem to recall lying the engine/gearbox unit on its side (the clutch side) on something soft,
and maneuvering the frame down over it and attaching the iso bolts.
And stand it up and continue from there.

The workshop manual details something similar, and the factory also.
But maybe they had several helping hands to simply lift the engine/gearbox unit into place.
The kickstarter HAS to be removed for this operation.
 
Rohan said:
I seem to recall lying the engine/gearbox unit on its side (the clutch side) on something soft,
and maneuvering the frame down over it and attaching the iso bolts.
And stand it up and continue from there.
Click to expand...

I believe that's how they did it at Andover.
Frame replacement
 
Thanks LAB, I've not seen that pic before.

It does raise a question though - it shows the clutch side uppermost.
The opposite of how I did it.

Since I seem to recall the clutch housing won't fit through the frame space (?),
and there is clearly a hoist control there in the pic (and engines on the floor),
did they lower the engine/gearbox unit down into the frame.
They had to have..... ?

Without the hoist, its easier for one person to lower the (bare) frame down onto the engine/gearbox unit.
 
This is very helpful information!

Thanks a lot for that.
I have a hoist and plenty of soft things to protect everything. I think i can do the bent rolling frame to straight rolling frame swap in less than a day this way.

I think i will try the frame over engine option first. Even with hoist, the other way around seems a little risky for paint damage.
 
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