Clutch/gearbox

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Tremmy
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Joined: Sun Jul 10, 2022 8:38 am
Location: Cornwall UK

Clutch/gearbox

Post by Tremmy »

Please be patient, I have a series of questions regarding my CP burman gearbox, I had to replace the main bearing which led to pinion ratchet and other parts, so the gearbox is now back together but tension on clutch lever is quite strong, can someone please tell me the correct length & diameter of rod thrust shaft for 4 plate ??
I have adjusted sleeve for clutch lever fork in both directions,
Any help will be greatly appreciated.
Cheers
g80csp11
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Re: Clutch/gearbox

Post by g80csp11 »

9.7/8" on 350 , and 10.1/8" on 500 for 1946 , check the spares list as it list length
what year is your bike ?
http://archives.jampot.dk/book/Spares_l ... ingles.pdf
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clive
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Re: Clutch/gearbox

Post by clive »

Some possibly relevant thoughts.
The clutch rod adjustment on the CP box is in for out, ie to reduce the pressure the pushrod exerts, turn the nut under the little cover inwards. the clutch cable should be slacked off whilst making the adjustment.
"but tension on clutch lever is quite strong" Is the cable well oiled and does its routing have no tight turns? Assuming the cable is ok, the pressure felt at the lever is probably related to how far the clutch spring nuts are screwed in rather than the pushrod length. Turn them out half a turn and the pressure at the lever will feel less. The trick is to balance the feel at the lever with the risk of clutch slip. If in doubt I test this by putting the front brake on and seeing if I can stall the bike when letting the clutch out with a few revs above tickover. Needs a good surface or the front wheel slides forward anyway!
clive
if it ain't broke don't fix
Tremmy
Posts: 8
Joined: Sun Jul 10, 2022 8:38 am
Location: Cornwall UK

Re: Clutch/gearbox

Post by Tremmy »

Thanks for your feedback, my bike is a 1947 350, I have been restoring for past 12 months. I'm not quite at the start up stage so difficult to stall. It's 4 hole plate & yes the manual says 9 & 7/8 as you identified.there is minimal tension on both sides (springs & but under cover).
It is broke so I have to fix !!
Tremmy
Posts: 8
Joined: Sun Jul 10, 2022 8:38 am
Location: Cornwall UK

Re: Clutch/gearbox

Post by Tremmy »

Also to note the cable is brand new.
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clive
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Re: Clutch/gearbox

Post by clive »

Tremmy wrote: Thu Nov 03, 2022 6:09 pm Also to note the cable is brand new.
And oiled?
clive
if it ain't broke don't fix
SPRIDDLER
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Re: Clutch/gearbox

Post by SPRIDDLER »

BTW - The correct h/bar clutch (and front brake) lever have a distance of 7/8" between the centre of the lever pivot bolt and the centre of the cable nipple. If it's greater than 7/8" the action will be heavier than with 7/8".
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56G80S
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Re: Clutch/gearbox

Post by 56G80S »

Spriddler is spot on, I found a real difference when I fitted the 7/8" centres lever (which ironically I had anyway but hadn't fitted).

Johnny B
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Re: Clutch/gearbox

Post by Triumph-Legend »

A passing note.
Chasing some GB gearbox parts a while back, (a couple of years), I spoke to Russel motors of Battersea. Apparently they have lots of original factory parts for the earlier Burman CP boxes but far less for the GB types. It might be worth giving your CP box a going over whilst the bits are still available.
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