Commando MK11 front Fork Question

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thunderbolt

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I have just pulled the front forks on my '74 850. On measuring the long spring in each fork leg they come in at 15" exactly. The manual tells me they should be 18.687".

Does anyone have an explanation?

Also the holes in the damper tube are in a different location to the pictures I have seen of other Roadholder damper tubes.

Thanks Don
 
thunderbolt said:
I have just pulled the front forks on my '74 850. On measuring the long spring in each fork leg they come in at 15" exactly. The manual tells me they should be 18.687".

Does anyone have an explanation?
Click to expand...

I can't offer an explanation but the springs should be 18.687".



thunderbolt said:
Also the holes in the damper tube are in a different location to the pictures I have seen of other Roadholder damper tubes.
Click to expand...

Well, without a descripition of the actual hole locations or what others you have seen it's difficult to answer.

Yours should be the 'late' 061888 type with holes in the tapered section'?

061888
https://andover-norton.co.uk/en/shop-details/15684/fork-damper-tube-8-7-8-06-0299-
 
thunderbolt said:
On measuring the long spring
Click to expand...
Is there more than one spring in each leg? If there is a 15" and a 3" it would indicate that they are aftermarket springs. Some guys would use a short soft spring and a stiffer long spring with the thought that it would give a progressive feel. Original equipment would have been one long spring as L.A.B stated.
 
When you make a coil spring shorter - it becomes stiffer.
To cut off three inches and replace it with a spacer the same length, you stiffen up the suspension.
Perhaps you have a spacer or you could add one.
 
Les/The holes are on the tapered section of the damper - so looks standard for my year. I had seen other dampers with the holes closer to the end of the damper but I guess they were from an earlier model.

XTINCT/There are two springs in each leg. One is 15" and the one on top of that is 3 3/8". The longer spring has not been just cut shorter. Both ends of the long spring have been finished off correctly with flat ground ends.

Dutch/Refer above; No spacer involved or needed.

I have removed the damper rod and it is pitted on the bottom section where water has got in I would suggest. Will this allow different damping characteristics with a narrower rod in sections passing the the damper cap, etc.

Thanks
 
thunderbolt said:
The holes are on the tapered section of the damper - so looks standard for my year. I had seen other dampers with the holes closer to the end of the damper but I guess they were from an earlier model.
Click to expand...

Yes, 'early' damper tubes have holes below the taper.

thunderbolt said:
I have removed the damper rod and it is pitted on the bottom section where water has got in I would suggest. Will this allow different damping characteristics with a narrower rod in sections passing the the damper cap, etc.
Click to expand...

The rods and caps aren't expensive so it's a good idea to replace them both.
 
A bit more advice please?

When I disassembled the forks there was no fork spring top hat alloy locating spacer. Just a flat washer and nyloc nut on the top of the damper rod. Should I use one of these top hat locators in each fork leg?

When I was preparing to order the damper valves for the forks I came across the fact that there are two types.
Fork Damper Valve, SPEC A @ .677" - .678". Fork Damper Valve, SPEC B @ (.671" - .674").
How do I decide which ones I should order. BTW these specs and parts are from RGM.

Thanks Don
 
thunderbolt said:
When I disassembled the forks there was no fork spring top hat alloy locating spacer. Just a flat washer and nyloc nut on the top of the damper rod. Should I use one of these top hat locators in each fork leg?
Click to expand...

At the top of the standard spring/rod assembly should be a (steel) "Fork spring location bush" NM25003, item '23', and a thin nut, item '15'.

https://andover-norton.co.uk/en/shop-details/17382/fork-spring-location-bush-nm25003-
https://andover-norton.co.uk/en/shop-details/17601/nut-3-8-unf-plain-thin-26078-06-0347-

thunderbolt said:
When I was preparing to order the damper valves for the forks I came across the fact that there are two types.
Fork Damper Valve, SPEC A @ .677" - .678". Fork Damper Valve, SPEC B @ (.671" - .674").
How do I decide which ones I should order. BTW these specs and parts are from RGM.
Click to expand...


According to RGM:

ORIGINALLY THREE SIZES OR TOLERANCES OF DAMPER VALVES WERE SUPPLIED, IDENTIFIED BY A LETTER AFTER THE PART NUMBER. THE EXAMPLE HERE IS ONE WE HAVE HAD MADE AND IS A CLOSE TOLERANCE VERSION ORIGINALLY GIVEN THE PART NUMBER 14118A. ITS TOLERANCE WOULD BE .677" - .678" (17.18 - 17.2MM). WE ALSO STOCK 14118B WHICH IS NOT AS WELL OR CLOSELY FINISHED AND IS A LITTLE SMALLER (.671" - .674") THE CHOICE ALLOWS FOR A LITTLE EXPERIMENTATION SHOULD YOU BE SO INCLINED. 14118B WOULD BE STANDARD ISSUE.
Click to expand...

"A" is probably the better option.
 
Thanks Les, I will place the order with RGM now.

One more question if I may??

Is it considered better to go with the short fork gaiters which leave a large section of the staunchions exposed to the elements or the longer concertina gaiters for the front forks? Mind you we don't have much in the way of elements in Sydney, Australia.

Thanks Don
 
thunderbolt said:
Is it considered better to go with the short fork gaiters which leave a large section of the staunchions exposed to the elements or the longer concertina gaiters for the front forks? Mind you we don't have much in the way of elements in Sydney, Australia.
Click to expand...

Your choice really but long gaiters should extend the life of the seals.
 
" Mind you we don't have much in the way of elements in Sydney, Australia."

It's dried up bugs and stone chips that eat the fork seals.
 
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