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Commando - rear subframe

Submitted by paul_smith on Tue, 28/04/2015
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Commando

Hi all,

Did a daft thing last weekend and pulled away with a cable lock around the rear wheel across the top of the rear light fairing.

Its cracked the fairing and bent the T bracket under the fairing - I straightened that out and fibreglass the fairing back together. But when I put the seat on it rocks back and forth as the rear rubbers are nolonger touching the top of the rear mudguard.

Is it possible the force has pulled the rear sub frame down, or maybe just bent the mudguard.

I managed to reduce the rocking of the seat by pushing the mudguard up in the slotted brackets and then tightening - but I did not need to do this prior to my error with the lock.

What do you think? Is there a way to check the subframe is still in its correct position?

Thanks - Paul.

Submitted by alan_throssell on Tue, 28/04/2015

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Previously paul_smith wrote:

What do you think? Is there a way to check the subframe is still in its correct position?

Hi Paul, I have an original Commando Workshop maual and in section F, fig F4 shows "Frame Checking Data" for 750 & 850 frames. It is likely you have bent the rear loop downwards and this can be bent back to the correct position with some force. If you don't have the workshop manual I could scan the page for you.

Regards, Alan

Submitted by david_evans on Tue, 28/04/2015

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The drawing shows the rear frame loop to be parallel to the bottom frame rail. If you set the bike up on it's centre stand and level the bottom frame tube with a spirit level, then check if the rear loop is also level. If its not get a fence post under it and get a fat b----rd to sit on it while you do your Geoff Capes impression.

If after you have done this and should the frame have been powder coated then scrape all the powder coating off aft of the top damper mounts and repaint. My frame loop was bent up for years unknown to me after a slide off on ice. when I came to re furbish the frame, rust had tracked along inside the nice shiney powder coating. No more powder coating for me two pack is the way ahead IMHO

Submitted by Anonymous (not verified) on Tue, 28/04/2015

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A useful document which I did not have - thanks Alan.

Here's another way of bending the rear loop - unsurprisingly, this Commando developed the same problem on its way to Clonakilty in 2003.

Attachments 02_commando_m-jpg

Submitted by peter_stowe on Wed, 29/04/2015

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I did the same about 20 years ago.

At work the looped some rope around the end of the frame loop/sub frame, the lifted the bike up with a fork lift truck. By putting weight on and pulling the bike down we straightened the frame until it was right to the eye and the seat fitted properly.

I know it's not the highest tech frame straighting, but it was twenty years ago and the bike has done many thousands of miles since.

Check your wheel spokes, as the chain lock slightly bent one of mine, but that is still in the wheel.

Submitted by barry_carson on Wed, 29/04/2015

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surprised to see on the frame drawing that the main frame tube is only 16 gauge i thought it would have been a lot more beefy than that .Baz

Submitted by paul_smith on Sun, 03/05/2015

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Hi all,

So pretty sure the rearseat sub frame is bent down - even without a spirt level I can see just by looking at the bike side on and compairing with the bottom frame rail.

Is there a specific or best method to get it to its correct position?

Thanks - Paul.

Submitted by paul_smith on Fri, 22/05/2015

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Hi all,

Quick update on the solution...

Rode to Andover and gave the bike to Norman White - he pulled the subframe straight and then fabricated some new brackets (replacing the orginal top shock brackets) that extend along the frame forming a longer gusset than the orginals.

So all sorted and ready for some luggage.

See you in Ireland next weekend - regards Paul.

PS - Norman should have had his surgery completed now - best wishes to him for a quick recovery.

 


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