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Author Topic: THREE SPRING CLUTCH UPGRADE  (Read 1904 times)

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Offline Brooklands

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THREE SPRING CLUTCH UPGRADE
« on: January 08, 2013, 02:08:26 PM »
This item is about improving the three spring clutch, and also introducing a degree of adjustability. The standard clutch is cork based, with a plain plate inboard and a plain faced outer cover assembly, which is lifted away from the plates by the clutch push rod when the lever is pulled. This item is about the 'modern' friction plates and the two types of plain plate - thick & thin.
Starting from the outside, inspect the inner face of the outer cover and also its centre, where the rod presses. My outer cover was both scored and corroded, and initially I skimmed most of the poor areas in the lathe, but resorted to a far simple solution which was to put an extra thin plate up against it - I assembled it loose, with a few spots of Loctite and it now seems permanently bonded, which is fine!
Then check the locking nut/screws - mine were chewed up, so I made some more - dimensions in photos are just guides - if it fits, that'll do!
Check the spring lengths/condition - if in doubt, fit replacements. Check the cups are good and the small spacer tubes, which may be missing - these are discarded to allow more tension to be applied to the spring in an attempt to stop clutch slip. The brass nuts actually should lock down onto the spacer tubes and be firmly fixed, helping to stop the clutch skewing.
The original standard tubes are 1/4" ID, 3/8" EXT, 15/16" long, mild steel. If you are upgrading the clutch then you may need to make spacers of a different length as the spacers control the spring tension 'at rest'.
Continued....
Norfolk 'n good!

Offline Brooklands

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #1 on: January 08, 2013, 02:09:39 PM »
And..
Norfolk 'n good!

Offline Brooklands

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #2 on: January 08, 2013, 02:17:29 PM »
The brass nut & spacer tubes have no provision for adjustment. If you look at your assembled clutch when you pull the lever in you may find it doesn't lift evenly. The outer cover is actually balanced on the clutch rod and may topple one way or another dependent on spring tension. If it is wonky it won't work properly. To introduce some adjustment make up some washers as shown - dimension not critical - and place them in the base of the cups, under the spring. These will pre-load that particular spring and give it an increased tension.  Re-lock the brass nuts and see whether the clutch lifts evenly, and play with adding & removing washers until you get it as good as you can.
You can use the same washer idea to increase clutch spring tension - rather than shortening the spacer tubes. Just add the same number of washers to the tubes to give more grip (and a heavier to pull lever).
Norfolk 'n good!

Offline Brooklands

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #3 on: January 08, 2013, 02:30:39 PM »
Sorry, mis-use of words - the washers are added to the cups as per pic, not the spacers.
The two plate clutch is a bit marginal on grip and there is enough room to add an additional friction plate and plain plate. This gives considerably more grip without increasing lever pressure, and provides a smooth clutch too. The extra £20 or so is well worth spending and makes the clutch a 'fit & forget' assembly. The Surflex type plates are not much affected by oil and will last most of us out.
The back plate, which goes in first, should be the 'thick' type, followed by alternating friction & thin smooth plates. You may not need an extra thin smooth plate under your outer cover if it already has a good face. Apply a spot of grease to the centre of the outer face, where the clutch rod touches.
Reassemble the spacers, cups, springs & nuts, and lock down the brass nuts. The clutch rod itself may need altering slightly, but there may be sufficient adjustment on the internal adjuster (see service sheets). If the rod is short, cut it in half and put a 1/4" ball bearing in the middle. Make sure that there is some free play at the rod and it is not binding by pressing against the inside of the clutch cover. Make sure there is 1/8" play at the lever too.
Ideally, ride the bike with the primary cover off (tuck your skirts in), and get everything running properly before sealing the thing up and adding the lube of your choice.
Joe
Norfolk 'n good!

Sergeantwoodie

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #4 on: January 09, 2013, 04:02:42 PM »
Sergeantwoodie
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Thank you to Brooklands
« on: Today at 12:32:51 PM »Quote
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For taking the time & trouble to post the comprehensive advice on the 3 plate clutch , great stuff,. Not taking anything away from it but just two pence worth from an fogey who has dealt with many C12 clutch problems oner the years for other owners. I am talking re the other side Gear box side! the operating lever within the Gear box,  people trying to get the outer cover back on , have not taken sufficent care to make  sure the operating  lever  is  in its proper location. What happens is  the push rod is not therefore   operated by the harden ball in the arm/lever it rests on the soft metal on the lever itself. Wears  an depression  and   clutch  adjustment requires constant adjustment. Another point the  thread in the outer cover wears, through hamfisted adjusting, instead  being the point of contact  for the operating lever,  the screw moves in and out  slightly again messing up Clutch control. Many will already know this  but thought if one knows the pitfalls pass it on  thats what  helpful sites are all about.

Online timsdad

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #5 on: January 09, 2013, 05:08:29 PM »
I find that a 1/4" roller bearing, instead of a ball, in between the two sections of push rod works better because it spreads the load and prevents the ends of the rod from mushrooming out.

It also helps if the new ends of the push rod are hardened by heating up red hot and then immediately plunging into mineral oil.

Ray
Just a motorcyclist.

Online chaterlea25

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #6 on: January 10, 2013, 09:24:20 PM »
Hi All,
As Joe points out the clutch pressure plate balances on the end of the pushrod, Not a great idea at the best of times :(
A solution I have used which works well on several different make/model clutches is to fit a radial thrust bearing (kit??) this comprises of a short mushroom pushrod onto which sits the radial bearing
The opposite thrust face is the threaded adjuster normall used in the fancy SRM type alloy pressure plates, I knock out the hardened pad in the centre of the steel pressure plate, and fit the threaded adjuster with either a nut either side or just one on the outside, lock this up solidly or if theres room inthe clutch/primary case an adjusting nut can be brazed to the pressure plate, to retain adjustment
The outer end may need cutting back depending on primary cover clearance

The parts are available as spares from SRM, You dont need to buy the  complete pressure plate kit !!!!!
http://www.srmclassicbikes.com/catalogue/index.php?target=products&product_id=40,

Specify, pusher for 1/4in. pushrod, thrust bearing, adjuster and locknut(s)

HTH
John


Online chaterlea25

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #7 on: January 15, 2013, 10:35:19 PM »
Hi All,
I found the photos showing the thrust bearing mod and parts
This is shown on a Rudge clutch but the same will apply to many different makes and models
Regards
John

Offline Jim fell

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #8 on: October 16, 2014, 10:40:54 AM »
Hi have a 52 c11 I have just put in the modern clutch plates not cork do thes still require oil or not thanks  and great helpful site as I am  a Farley new comer to this thank again Jim

Online Owen

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #9 on: October 16, 2014, 12:52:55 PM »
Some people run with and some run without oil. For me i prefer ATF fluid in my primary chain case (running cork). It makes the clutch action light and smooth. Others spray a variety of fluids e.g. chain lube.
its really up to you.
1945 C10 & C11
1953 C10
1953 C11 x 2
Still looking for an Original 350 side valve C12

Offline Jim fell

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #10 on: October 16, 2014, 02:27:45 PM »
Thanks Owen i will try the ATF as I drive a auto thanks Jim

Online ianinglis

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #11 on: October 16, 2014, 04:37:02 PM »
dont be surprised if it pisses out all over the floor (or the frame and final drive chain)
perfectly normal ;)


ian
BSA C10L 1956 - JFO 588
BSA C10L 1954 - MVE 107
RM6 RALEIGH RUNABOUT
ENFIELD DIESEL KUBOTA OC 95
BSA M21 RIGID RKN 816
CBF 1000
BSA ARIEL 3

Online Owen

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #12 on: October 16, 2014, 04:42:57 PM »
The oil in both my C's primary chain case does not leak out.
1945 C10 & C11
1953 C10
1953 C11 x 2
Still looking for an Original 350 side valve C12

Online ianinglis

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #13 on: October 17, 2014, 07:07:01 PM »
must be empty then ;D ;D ;D


ian
BSA C10L 1956 - JFO 588
BSA C10L 1954 - MVE 107
RM6 RALEIGH RUNABOUT
ENFIELD DIESEL KUBOTA OC 95
BSA M21 RIGID RKN 816
CBF 1000
BSA ARIEL 3

Online Owen

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Re: THREE SPRING CLUTCH UPGRADE
« Reply #14 on: October 17, 2014, 07:14:02 PM »
It's amassing what Tena lad's can do for you!!!!!!
1945 C10 & C11
1953 C10
1953 C11 x 2
Still looking for an Original 350 side valve C12