6B Clutch Slipping - Help!

[Ernie Phillips]

In prep for going to Combs later this week, my son rides his '72 Six Day around the block and reports back, "Dad the clutch is slipping."  I confirm the condition (slips in higher gears, 3+, when operated in power band).  Prior to all this, the bike has been ridden for 2 hours with no problems.
 
Externally, the clutch cable has slack.  The gearbox has oil (10-30.) I haven't gone into the side case yet.  What should I be looking for?  I have a spare 5A motor.  Will the 5A clutch fit the 6B?


Ernie P.
Chattanooga, TN

[Randy Kirkbride]

Ernie,
Did you make sure that you have your countershaft sprocket nut is torqued to the correct tightness. This is from the voice of experience.

[Kip Kern]

Ernie, The clutch will interchange if it is a later 5A going to a 6B.  The early 5A's had shallower clutch basket (39.5mm vs 41.5mm)  Also, once the clutch is installed and shimmed properly, put the clutch outer clutch cover on and be sure the actuator screw is 1/3 turn away from depressing the actuator. Another helpful item too is to make sure the steel plates are clean and not pitted, and to clean, degrease the organic plates and run them over a very fine wire wheel to deglaze them.  Let her rip!

[Ernie Phillips]

Randy,  Never thought about sprocket nut.  I'll check.  (gives new meaning to thinking outside the "(gear) box".

Kip, Thanks.  I'll check my 5A spare for interchangability and make sure 1/3 back off.

I'll leave a paying job early today to go twittle with a +30 year old bike.  This is an expensive hobby!

Ernie P.
Chattanooga, TN

[Merlin]

............ditch the 10/30 and put in ATF...........

[[email protected]]

My clutch does not slip but will drag off the start and out of the gate? What can cure that and hoe does the ATF help?
            Thanks, Stork  400 Mint

[Kip Kern]

Ernie, The clutch will interchange if it is a later 5A going to a 6B.  The early 5A's had shallower clutch basket (39.5mm vs 41.5mm)  Also, once the clutch is installed and shimmed properly, put the clutch outer clutch cover on and be sure the actuator screw is 1/3 turn away from depressing the actuator. Another helpful item too is to make sure the steel plates are clean and not pitted, and to clean, degrease the organic plates and run them over a very fine wire wheel to deglaze them.  Let her rip!

[Ernie Phillips]

Randy,  Never thought about sprocket nut.  I'll check.  (gives new meaning to thinking outside the "(gear) box".

Kip, Thanks.  I'll check my 5A spare for interchangability and make sure 1/3 back off.

I'll leave a paying job early today to go twittle with a +30 year old bike.  This is an expensive hobby!

Ernie P.
Chattanooga, TN

[Merlin]

............ditch the 10/30 and put in ATF...........

[[email protected]]

My clutch does not slip but will drag off the start and out of the gate? What can cure that and hoe does the ATF help?
            Thanks, Stork  400 Mint

[Ernie Phillips]

Clutch update:  Upon disassembly found gummed up & glazed friction plates.  I deglazed & cleaned everything up.  Filled box with ATF.  Rode 40 miles Friday in hilly Combs terrain -OK.  Didn't start slipping until late in day Saturday after 3 specials.  Made it through 1st special Sunday but things were degraded so bad that Christopher called it quits at lunch break.  Good decision or he would have come in on a tow rope.

Besides old age, I think contributing factors to the clutch problems is a very powerful engine with no flywheel (homebuilt ignition).   Also, and maybe the main factor is that the rear tire is too big - 110/100 dunlop D752.  The big tire came on the bike, was like new, and decided to keep it on.  Bad choice on my part.  When this particular engine "hits" something is going to move.  Better to spin the tire than burn up clutches.

Are there any upgrades that I can do besides new parts?  Any comments on the "Big Tire" theory, recommended tire -size, -brand?  (I ran a Cheng Chen 3.50 on my steel tanker, looks dinky, but pulled an amazing hole shot)

Ernie P.
Chattanooga, TN

[Ernie Phillips]

Got new Friction Plates from Terry Everett - OEM Sachs.  I'm a happy guy.  Looking at the new plates, I can see that they are much thicker than the old ones which now appear to have exceeded their service limit.

Anydody care to comment about the 12 spring clutch mod?  I think I could to this in my shop ...  I want a "bullet proof" clutch.  Or will the stock clutch (9 springs) with new components hold up?

Ernie P.
Chattanooga, TN