Commando Frame rake repair info needed

Hi All,
I have a 73 850 Commando frame which I'm hoping to use as a basis for my latest rebuild which will use a 72 750 engine and 850 'ANG' yolks.

I was doing some basic frame geometry checks and using an inclinometer and noticed the rake angle is approx 67 degrees whereas the factory spec is 63 degrees. I'm reasonably confident my measurement is accurate as according to the inclinometer the lower frame rails are sitting dead level on blocks of wood and the rear frame loop is also level.

There is evidence of some kind of repair on the lower frame top tube and I'm now wondering whether this frame can be salvaged as it might mean bending the rake back by 4 degrees.

I live fairly near to Motoliner Maidstone Kent who have a good reputation for repairing/aligining frames but before I go there I would like some thoughts on whats happened to this frame and whether its worthwhile reparing.



All info welcome

gunnag said:

73 850 Commando frame......

I was doing some basic frame geometry checks and using an inclinometer and noticed the rake angle is approx 67 degrees whereas the factory spec is 63 degrees.

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The 850 frame is supposed to be 62 degrees (750 is 63).

That looks like some one purposely increased the rake by adding a longer piece of tubing. It'd be interesting to see how it rides.

concours said:

That looks like some one purposely increased the rake by adding a longer piece of tubing.

Click to expand...

I make that less rake, as the angle from the vertical is 23 degrees instead of 28.

Also note the very different quality of weld on the top and bottom of the head tube. Maybe its the angle.
Possibly beyond what a normal motorliner place is equipped to deal with (question mark) DAMHIK.
Lots of due diligence and careful questioning.

Looks like somebody stuffed the bike into an immovable object. The lower tube was repaired, probably to replace a kink in the tube as the headstock moved backwards. A close look at the upper tube about 3 inches back from the headstock reveals a discontinuity in the tubing, consistent with the headstock being pushed down and back, then more or less straightened out (minus the missing 4/5 degrees of rake). Let us know what the frame shop will say. Most frames you find are bent anyway, so if they can fix it for the cost of a replacement frame, you are ahead of the game.

Stephen Hill

It is probably more common to specify rake in terms of degrees from the vertical. The difference of one degree in rake between the 750 frame and the 850 frame does actually create a handling difference. If I was doing the job for my own use, I'd go with the early 750 rake even though it carries slightly more risk of a crash under extreme circumstances. I iike quicker steering, however it is not for everyone.

Get the center line of the rear iso mount and Z plate holes level and try again, frame tubes could be anywere , seat rails should be level but that's also a joke.
I see Andover sell that tube, and all others aswell

The joint between the headstock and the spine is very strong and almost impossible to move, however the frame is easily bent everywhere else. As Splatt says level the rear iso bolt and try and establish if the frame has been bent sideways (parallelogrammed), mine was, the give away was trying to get the front iso bolt in without distorting the front rubber. Rode it for years like that :roll:

Same old Commando frame glitch, this is an old story from when Norton themselves (who are NOT frame builders) there was an early batch of Commando frames where the small tube under the main spline tube was omitted from the chassis until Ken Sprayton told Norton to fit one, these frame were known as widowmakers in the USA. Small tube has received some attention in the middle from a welder’s torch at some time, if you go to use a Motorliner jig they will only look at it with preferably the engine and swinging arm and back wheel intact.

Thanks for the comments guys, I spoke with Motoliner Maidstone and showed them some photos. They said they can pretty much fix any frame and have plenty of experience with Commando frames. They mentioned that in addition to the frame alignment jig they have a special tool which fits in where the engine cradle fits.

Anyway I'm taking the frame there on Saturday so we will see what they say.

Bernhard said:

Same old Commando frame glitch, this is an old story from when Norton themselves (who are NOT frame builders) there was an early batch of Commando frames where the small tube under the main spline tube was omitted from the chassis until Ken Sprayton told Norton to fit one, these frame were known as widowmakers in the USA. Small tube has received some attention in the middle from a welder’s torch at some time, if you go to use a Motorliner jig they will only look at it with preferably the engine and swinging arm and back wheel intact.

Click to expand...

no this is an 850 frame that dosent apply here

Today I got the frame back from Maidstone Motoliner who appear to be one of the few companies left in the UK capable of straightening motorcycle frames.

Apparently when placed in the jig, my frame showed various problems including a rake angle of 66 degrees, misaligned front and rear ISO mountings and a distorted rear loop on the left side. Clearly this frame had been in one or more accidents in the past.

They managed to pull the rake back to 63 degrees and didn't want to go to 62 degrees as they felt this may be too far to pull it. They mentioned that 63 degrees would result in slightly quicker steering over the 850's 62 degrees but didn't think this would be an issue. They also straigntened the odd looking lower upper frame rail which was a previous repair.

Maidstone Motoliner have a dedicated Norton Commando jig which fits in the front and rear ISO mounts. This jig is fitted when making adjustments to the frame and helps ensure the swinging arm etc. is perfectly aligned with the frame so hopefully the bike will handle. I also had the swinging arm measured and adjusted and it did need some trueing :x

This is the first time I have needed a frame jigged and checked and I have no hesitation in recommending this company, see Maidstone Motoliner

The frame and swinging arm are now at the powder coaters and should be back with me by Friday, which is when the reassembly will begin

Any ideas on how "they managed to pull the rake back to 63 degrees"? Great honking levers? Hydraulic press? Heat? Inquiring minds with nodding frames want to know.

Stephen Hill

Hi Steve,
I asked a similar question and the answer is something like the following:-
- the frame is rigidly secured in place in the jig using clamps and frame distortion/accuracy is then determined by taking measurements at varyious reference points
- Where the rake needs pulling out, a temporary yolks are fitted into the headstock using the upper and lower bearing seats as reference points, a long steering stem bar with a pointed end is passed through the temporary yolks and the pointed end is measured against a ruler on the jig
- Heat is applied to the frame in varyious positions as needed to make it pliable and then several tons of force is applied from the base of the steering stem lower bearing hole.The top bearing is prevented from moving forward by a stop bar. Several pulls may be needed to get the required rake angle.

Have a look at This video from about 10 mins 36 secs onwards. This essentually uses the same process but uses a cold pull to adjust the metal.

I had my frame checked at the end of the last year by a guy here in NZ with a similar rig when it was apart and he was doing some welds on it for me. Checked out OK and straight!

Strangely enough, when I went down to pick mine up, he also had a HD on the rig. Said he did a lot of them...

https://rapidartnz.com/Services/ChassisS.htm (it looks like his web site is busted today for some reason)

Is that Steve Bridges in Hamilton?

Yes

Bernhard said:

Same old Commando frame glitch, this is an old story from when Norton themselves (who are NOT frame builders) there was an early batch of Commando frames where the small tube under the main spline tube was omitted from the chassis until Ken Sprayton told Norton to fit one, these frame were known as widowmakers in the USA.

Click to expand...

As already mentioned, this doesn't apply to 850 frames.

However, it was LOT more than "an early batch" that were the widowmaker frames - it was quite a considerable run of production, since it took a while for the frame breaking problems to show up, and even longer to get NV to do anything about fixing them, and Reynolds to make frames with the reinforcing bar underneath the main spine.

I'm curious why they could get to 27 degrees, but not 28 ?
That is only a very small increment....

The local frame guy here has a frame jig that is a large open steel cube, nearly a tons worth, that he can clamp and hold frames in - and uses a variety of hydraulic and chain adjustments etc that can push pull and drag frame bits in all directions. He is Harley trained to do this, but has adapted it to do about everything and is very in demand.
His queue of girder forks requiring attention would make most old bike makers blush...