Author Topic: C11 fork clunk  (Read 414 times)

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Offline lister man

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C11 fork clunk
« on: November 21, 2020, 08:41:04 pm »
Hi again , My question this time is my 1946 c11 makes a clunk when the forks return up over bumps can make it do it also buy pulling up sharply on handle bars . My forks are teles . Has anybody else had this problem?

Online sidevalve

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Re: C11 fork clunk
« Reply #1 on: November 21, 2020, 09:37:35 pm »
Damping oil ?

Online Owen

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Re: C11 fork clunk
« Reply #2 on: November 21, 2020, 09:45:25 pm »
Top bush not shimmed and moving against locking ring?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11

Offline BSAc11g

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Re: C11 fork clunk
« Reply #3 on: November 21, 2020, 10:15:50 pm »
The forks have only one way damping so you can get a topping out klunk hen the forks extend to their maximum length.
Bike Beesa
Trevor

Offline ThomasC11

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Re: C11 fork clunk
« Reply #4 on: November 22, 2020, 07:51:47 am »
I have the same. As Trevor says, you need to accept it and watch out for big bumps on the road.
1946 BSA C11
1937 Sunbeam Model 9
... and a scratched Hyundai

Online Vreagh

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Re: C11 fork clunk
« Reply #5 on: November 22, 2020, 11:12:35 am »
I've not tried it on the C11 but on the larger BSAs, the Eddie Dow 2way damper rods works a treat. Simple to fit onto the top nuts.

Online camman3

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Re: C11 fork clunk
« Reply #6 on: November 22, 2020, 01:39:22 pm »
As said, they all clunk, part of the reason they are called old clunkers ;)
The shims on bushes just stops them rattling up and down in normal action.
A lot of us wont have experienced this particular clunk, as our generous proportions and low speeds prevent it ;D
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Offline lister man

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Re: C11 fork clunk
« Reply #7 on: November 22, 2020, 06:35:44 pm »
As said, they all clunk, part of the reason they are called old clunkers ;)
The shims on bushes just stops them rattling up and down in normal action.
A lot of us wont have experienced this particular clunk, as our generous proportions and low speeds prevent it ;D
Graham


I weigh 10 stone so maybe need a few more stone :)  I'm currently running it with 20 w oil in forks, I must admit it has done it since I bought it 6 months ago, thanks to everyone for your input


Online camman3

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Re: C11 fork clunk
« Reply #8 on: November 22, 2020, 06:51:51 pm »
30w or even 40w may be better...even for your diminutive stature  ;)
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Offline lister man

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Re: C11 fork clunk
« Reply #9 on: November 22, 2020, 06:55:51 pm »
Yes have some 30 oil so will try that, I wonder if the damper rods conversion will fit the c11 ?

Online camman3

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Re: C11 fork clunk
« Reply #10 on: November 22, 2020, 07:08:52 pm »
A good accurate 1/4 pint per leg will help as well.
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Online Owen

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Re: C11 fork clunk
« Reply #11 on: November 22, 2020, 07:47:45 pm »
I run sae 20 and i'm 15 stone.
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11

Online Pete

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Re: C11 fork clunk
« Reply #12 on: November 22, 2020, 07:56:10 pm »
I weigh fork oil, so only use a thin oil.

Online camman3

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Re: C11 fork clunk
« Reply #13 on: November 22, 2020, 08:09:24 pm »
  ;D ;D
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Online chaterlea25

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Re: C11 fork clunk
« Reply #14 on: November 22, 2020, 10:33:40 pm »
Hi LM
The early tele forks do not have the two little holed drilled in the stanchions that suck in some oil between the bushes and trap it there
as the forks extend, this stops the metal to metal clang as the forks top out
Its an easy modification to do, I am off to hospital tomorrow for a new knee joint so will not be able to measure up the stanchion holes for you, hopefully one of the others here will have a stanchion to hand ??
That and shim the top bushes to the circlip if there is movement between them
Yes the Dow type dampers will fit, then you need thinner oil or they will be too stiff

John