Forks Seized?

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Re: Forks Seized?

Postby clive » Tue Jan 19, 2021 10:25 pm

are you trying to compress the forks with at least on side of the wheel spindle fixing loose? The fork stanchions may be faintly bent and if both sides of the spindle are locked up this can prevent any movement. Even without bent stanchions I always leave one side loose and bump the forks up and down before locking the other side up. This gets the whole lot in line, Don't forget to tighten the loose side though, especially if you do the work just before taking the bike for an MOT. :oops:
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Re: Forks Seized?

Postby Mick D » Wed Jan 20, 2021 8:48 am

Hi

The springs fitted to my FH, (which I think are the same as for an A10), have a free length of 10.375" - 10.75" and have 20.5 coils - I could fit the forks without a puller as the Ariel nacelle is installed afterwards, if you need a puller the thread at the top of the stanchion is 1 - 1/16" x 20 TPI.

Not sure what a G2 weighs but the FH is 410lb.

Iain_NCL wrote:The bad news is, having put it back together there's still no movement in them.


Can you explain this statement? the forks should compress / extend freely under hand pressure when assembled and 'on the bench', if they don't, something is wrong.

Regards Mick

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Re: Forks Seized?

Postby Iain_NCL » Wed Jan 20, 2021 9:05 am

clanger9 wrote:Very curious!

I have a set of Lightweight springs here. They're 45mm OD 34mm ID x 330mm

IMG_0353.jpg


Any use to you? I don't need them any more.


It is that! Thanks very much for the offer, but I think they would be totally different springs for these forks - the current springs are 48 mm OD x 260 mm. They sit on the outside of the fork tube between the slider ends and cups under the bottom triple clamp.

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Re: Forks Seized?

Postby Iain_NCL » Wed Jan 20, 2021 9:35 am

clive wrote:are you trying to compress the forks with at least on side of the wheel spindle fixing loose? The fork stanchions may be faintly bent and if both sides of the spindle are locked up this can prevent any movement. Even without bent stanchions I always leave one side loose and bump the forks up and down before locking the other side up. This gets the whole lot in line, Don't forget to tighten the loose side though, especially if you do the work just before taking the bike for an MOT. :oops:


I will definitely give that a go - I think it is the tension on the springs stopping it though. I'm a novice to a lot of this though, so still waiting for the moment when I go "oh, right, now I get it"

Mick D wrote:Can you explain this statement?


With the forks out of the bike, or even still in the bike but the tubes out of the top clamp (to take the compression off the springs) - the sliders move up/down fairly easily on the tubes (no internal springs). Once you put the forks fully back in, which would be very difficult without the winding tool it's definitely then no longer possible to move them by hand due to the spring tension. With the bike back together, and bouncing my weight on the front with someone watching, we haven't been able to see them move in the slightest - the springs just seem to keep them fully extended at the stop regardless of the weight on them.

These springs a bit shorter and not as many coils. About 260/270mm free. They are compressed to maybe 200/210mm with the forks fully extended by being clamped between the top of the slider and the cups under the bottom triple clamp.

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Re: Forks Seized?

Postby Mick D » Wed Jan 20, 2021 9:57 am

Hi

If you have the means to measure, my springs have a wire diameter of 0.212", they were easy enough to compress far enough to seat the top of the stanchion by hand.

Regards Mick

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Re: Forks Seized?

Postby clanger9 » Wed Jan 20, 2021 9:58 am

70mm preload is a lot. Perhaps you need shorter springs?
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Re: Forks Seized?

Postby Iain_NCL » Wed Jan 20, 2021 10:18 am

Mick D wrote:Hi

If you have the means to measure, my springs have a wire diameter of 0.212", they were easy enough to compress far enough to seat the top of the stanchion by hand.

Regards Mick


Thanks Mick, mine are 0.232" wire thickness and about 16 coils. To get the stanchion top in (taper fit), you need to compress with the tool and then do up the bottom clamps before unwinding the tool or they may shoot back out again quite dramatically!

clanger9 wrote:70mm preload is a lot. Perhaps you need shorter springs?


That's what I'm starting to think - they at least need to come off the stop with the weight of the bike on them to work. Unless I'm still missing something obvious (entirely possible), the combination of the excessive preload, spring stiffness and maybe some friction at the end of the travel is just holding them solid. Other possibility is they are a bit bent or similar but it's only showing when there's force from the springs?

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Re: Forks Seized?

Postby Mick D » Wed Jan 20, 2021 10:31 am

Iain_NCL wrote:mine are 0.232" wire thickness and about 16 coils


That's going to result in a very stiff spring, as you've discovered ;)

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Re: Forks Seized?

Postby SPRIDDLER » Wed Jan 20, 2021 11:40 am

I only know about AMC forks but are the springs going fully 'home' i.e. down to their correct position at the bottom of the sliders? Could the PO have added short supplementary (buffer?) springs which are still in place down there?
I realise it's only a 250 but they aren't the right forks so could they have sidecar springs still fitted from their previous bike?
It seems that the seller is being disingenuous by saying that the forks were O.K. when he sold it. :?
If you can identify precisely what model forks they are maybe the relevant owners club can advise length of springs or refer you to a spares list that gives spring lengths......
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Re: Forks Seized?

Postby Iain_NCL » Sat Jan 30, 2021 7:45 pm

Quick update, success! I have swapped the fork springs for some shorter, suitable ones and they work great. Also swapped the fuel tap for a push type and no more leaks.

Bike now handles well, I just have the rest to figure out, starting with the very lazy speedometer (reads about right, but 30 seconds later on).

Thanks everyone for your help!

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