N15/G15 CS Front Fork/Dampers

Information relating to the Matchless G15 or AJS Model 33 750cc twin. This also includes the G15 Mk II and the G15/45
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

N15/G15 CS Front Fork/Dampers

Post by Joker_Bones »

Anyone familiar with front forks on the N15 CS?
Mine are sticky and are making a creaky/clacky noise (always difficult to describe) as they start to compress.
Tried slackening the cap nuts, yoke and axle pinch bolts and working up and down, but that didn't help.
With the front wheel out the off side leg turned out to the sticky/creaky one.
The only diagram I could find was from the Norton & hybrids workshop manual:
Capture.JPG
This is the damper arrangement I found:
IMG_20220930_185922_edit_11189017334230.jpg
IMG_20220930_193435.jpg
IMG_20220930_190216.jpg
It sort of looks like the diagram... but is the extension to the damper rod a bit of home brew? Standard roadholder dampers extended to suit the longer CS stantions?
Whatever, the long part of the rod is straight but the extension is 3/16" cockeyed over its length... might be the cause of the stickiness
You do not have the required permissions to view the files attached to this post.
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: N15/G15 CS Front Fork/Dampers

Post by Groily »

With damper parts removed, I guess the stanchion moves smoothly in the slider, to rule out 'bush trouble' or 'bent' in that department'?
If so, I think you're probably right about the cause of the stickiness.
I'm not that familiar with them, but a long time ago I had to mess with similar, on a Norton set-up on an Oilfield café racer I had. All sorts of issues with relative lengths of the internals, resulting in the the forks being permanently part-compressed until I extended the rods inside. So I'd say a mix 'n match plus bodge is what you're looking at probably.
g80csp11
Member
Posts: 1567
Joined: Mon Jan 01, 1990 12:00 am
Location: WEST SUSSEX UK

Re: N15/G15 CS Front Fork/Dampers

Post by g80csp11 »

Andover Norton site shows parts , and whats available new
https://andover-norton.co.uk/en/shop-dr ... ks-n15-g15

looks very odd compared to picture on Andover Norton site , id be buying correct parts
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: N15/G15 CS Front Fork/Dampers

Post by Joker_Bones »

Yes, it was smooth as soon as I drained the oil out, though I can't quite figure what that indicates.
I've drawn up a diagram to try and get my head round what the relative lengths of the stanchions, rods and damper tubes should be. The lengths are provided by the very nice people at RGM who thoughtfully provide them on their website:
IMG_20221001_142053.jpg
It appears that I have the correct length stanchions, commando length damper tubes and over length extended rods.
I thought the valve at the end of the rod might bottom out in the damper tube, but it doesn't.
You do not have the required permissions to view the files attached to this post.
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: N15/G15 CS Front Fork/Dampers

Post by Joker_Bones »

Overall my forks are much more like the diagram above from the hybrids manual with external springs and AMC style slider extensions, the diagram on the Andover Norton site shows what I assume are more standard Norton roadholder type with internal springs... I just don't know enough about them to know what the "correct" parts are and which combinations belong to which models 🤔
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: N15/G15 CS Front Fork/Dampers

Post by Joker_Bones »

I only noticed the sticky forks when I was test riding the bike to see if I had fixed the non sealing head gasket...
Which I only noticed when my wife said she had bought a new bookcase and the bike had stop being an "installation" in the back room and I thought "I might as well have a go on it then"
One thing leads to another 😳
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: N15/G15 CS Front Fork/Dampers

Post by Groily »

Rather you than me on this JB.
After reading yours I had a look around too out of interest and soon got quite confused as to the options and possible mismatches.
From dipping into other forums, it seems there are others just as confused.
I was a bit lost with the Oilfield I mentioned as I had no idea what bits the bloke had used, so rather than fry what was left of the old grey matter, I simply turned up inch 'n a 'arf extension pieces for the damper rods, to screw into the top nuts. Did the job in terms of getting the thing to sit correctly and the bike handled well enough after the surgery . . .
What the eye doesn't see . . .
(Thinking of eyes, it's funny how not everyone likes things in plain view in back rooms. One man's treasured ornament may be his best beloved's pile of scrap - I have come across this too.)
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: N15/G15 CS Front Fork/Dampers

Post by Joker_Bones »

It is funny indeed... My wife spent the pandemic working from home in the back room. The N15 was in plain view in all the Teams meetings and was often the topic of conversation. She spoke, so it seemed at the time, proudly and fondly of it to those who asked. Its welcome seemed to pass around the same time as its use as a conversation piece and it has now been replaced by the bookcase.
Nomad
Posts: 4
Joined: Thu Nov 04, 2021 2:59 pm
Location: Surrey UK

Re: N15/G15 CS Front Fork/Dampers

Post by Nomad »

With the G15CS, N15CS it all depends on what year that the bike is from what the front fork spec will be. If it is from 1964 to 1965 it will have outside fork springs, and the G80CS internal dampers but an inch longer. The fork stantions will have a large nut to hold on the lower bush, with a special spacer. From 1966 to 1968 or the later bikes the stantions had a circlip to hold that lower bush on. The fork springs were as per the featherbed models or internal and the dampers were still one inch longer but as per the featherbed models. The 1963 Atlas Scrambler, and the later 1964 to 1965 G15CS, N15CS had front forks that were designed for use off road, for the desert or to race on the dirt tracks of North America.
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: N15/G15 CS Front Fork/Dampers

Post by Joker_Bones »

Thanks for the information...
I have 25" stanchions with the hex nut holding the lower bush on. External fork springs. 9" long damper units but I do not know by looking at them if they are G80cs or featherbed type. Which from your description seems like earlier off road type, however the bike was made 1966 according to the dating certificate, but who knows what modifications may have been made.

Have you finished your book on the hybrids?
I would like to read it!
📚
IMG_20221001_174821.jpg
You do not have the required permissions to view the files attached to this post.
Locked