backbone, how bent is OK?

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Ian, The backbone is an important part of the structural integrity on a Commando. I would be inclined to buy another frame. I bought one on e-bay for less than $200 a few months ago, just make sure you get the correct one. They all look similar but there are a number of differences depending on the year.
 
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Ian,

The hump in the top tube is typically where the two rear down tubes are welded to the top tube. I am going to stick my neck out and so they all seem to have a hump here. Check the frame for any signs of accident damage, and if it is an old frame, has it got the gusseting at the stem head
Rgd Richard
 

L.A.B.

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I have to agree with RichardS, this bow in the top tube seems to be normal!!!
 
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Frame &...gas tank

What is this beautiful alloy gas tank??? me wanting!
Philippe
 
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ahh yes... the alloy 2gal manx tank. but what good will it be if it does not have a good frame to live on!

i added some more shots of the frame and i think things may be worse. take a look.

http://www.ianmaclean.com/commandoproject/Sites.html

anyone have a frame for sale?
i may have a line on a complete highrider that needs rebuilt, so i guess i could use the two bikes for one good one... then part out some stuff that does not get used. it's only money.

-ian
 
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Bent Frame

Although I'm not a motorcycle mechanic, I am involved with "structures", and if it's bent, it's also "yielded" and that means that it doesn't take as much load that bent it to "fail it".

Not good.

If bending back, strengthen (doubler) the area around the bent section.
 

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Re: Bent Frame

rocketdoc said:
and if it's bent, it's also "yielded" and that means that it doesn't take as much load that bent it to "fail it".


The bowed top tube would seem to be a common characteristic of Commando frames though.
 

Ron L

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I wouldn't be as concerned with the backbone as those kinked down tubes. There's a good chance the steering head is out of line and would result in some pretty weird handling.
 
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yep, i noticed the kinked down tubes and other stuff like a long flat spot anlong the frame (looks like the bike took a good slide) after i looked at the top tube. lucky for me the guy who i bought it from has a matching number 74 highrider that is much more complete minus seat and tank (as you can see from the photos i don't care about that!). he is going to take the 71 back and i will just pay a bit more for the nicer 74. i will update the pictures sunday.

i am thinking about doing some sort of "blog" for the whole process.

bye for now
-ian
 
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I am also curious about the gas tank. Where did it come from? Very nice shape; not the normal flattened out Lyta type.
Duane
 
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My comment about the frame was based on Ian's description of the damage as I was unable to access the pictures. Having now managed to do so I concur with those who maintain that this amount of 'bow' in the backbone is standard. However I also agree that the damaged down tubes and other deformed tubes are a worry. This frame looks like an earlier model than 1971. It sounds like the option of the other bike is a good compromise, hopefully this comes with the later type frame with the cradle mounting for the centre stand and also the forward mounted side stand mount.
 
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