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Vintage Honda Owners,
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1964 CL72 Clutch will not engage.

Clutch, Transmission, Drive Chain, Sprockets
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skeptic
honda305.com Member
Posts: 16
Joined: Wed Apr 13, 2011 1:34 pm
Location: SoCal

1964 CL72 Clutch will not engage.

Post by skeptic » Tue May 19, 2020 4:34 pm

I have not ridden the bike but for about a mile several years ago when I took the bike in trade for some work.
At that time my recollection is that the clutch would not disengage. I assumed the plates were just stuck together. Also there were fueling/flooding and ignition issues which sidetracked me also.
I'm trying to get it running now. The service history of it is unknown. It has been taken apart previously by someone having unknown skills.
I took off the kick start side cover and if there was a ball bearing in there when I removed the side cover, it went missing at that time. I ordered a couple of those bearings, p/n 96211-10000
I loosened the side case clutch adjusting mechanism and backed it all the way in. I loosened the clutch cable so it is slack. I inserted the ball bearing, putting a lot of grease in the adjusting mechanism so as not to lose the bearing upon dis-assembly I installed the side cove, being sure to put the kick lever at about 11:00 p.m. The clutch was engaged, and the engine turned over before I tightened the screws holding on the case, As the last few turns of the screws were made, the clutch dis-engaged. The kick lever could go all the way through its stroke and the engine did not turn over.

I took off the clutch cover and removed the clutch plates. I wiped them off. and measured them. There were 6 plastic friction plates and 6 steel plates. The steel plates were all .060" (.152 mm). The friction plates were, from inner to outer most:
.120" 3.05 mm
.145" 3.68 mm
.115" 2.92 mm
.145" 3.68 mm
.117" 2.97 mm
.120" 3.05 mm
The total stack height of friction and steel plates alone was 1.140" (29.26 mm)
The metal oil guide that sits on top of the clutch basket, when installed, is properly keyed in the Clutch lifter joint piece and sits external to the clutch pressure plate.
It seems that the total clutch pack thickness is too little, that perhaps I either need thicker friction discs or more of them. Maybe a previous owner deleted the ball bearing in order to make up for worn out friction discs. Or am I missing something? Help please.
CL72, XL600R, XLV600, TL125, Bultaco Sherpa T 350

DJM
honda305.com Member
Posts: 512
Joined: Thu Oct 09, 2003 1:54 pm
Location: Chesterfield UK

Re: 1964 CL72 Clutch will not engage.

Post by DJM » Wed May 20, 2020 10:12 am

It's rare for the ball bearing to get lost as it's usually glued in place with the old hard grease, give the clutch lifter a good clean out and make sure that you haven't now got TWO bearings in there, this would cause problems like you have now.

You CAN''T adjust the clutch until you have the side cover in place and all the screws fully tightened.
Then loosen the 10mm A/F clamp bolt a couple of turns, no more and tighten the adjuster inwards (clockwise) until it stops, then back it off just a fraction until you get a bit of free play at the lever, tighten the bolt again and see how that works.

Your clutch pack is a bit of a mixture, the first steel plate should certainly be thicker than the others but what you have should at least get you mobile, you can fine tune it afterwards.

If you look on the old postings I think you'll find that there are more posts about clutches than any other subject bar none, makes interesting reading.

Good luck.

skeptic
honda305.com Member
Posts: 16
Joined: Wed Apr 13, 2011 1:34 pm
Location: SoCal

Re: 1964 CL72 Clutch will not engage.

Post by skeptic » Wed May 20, 2020 7:09 pm

Thank you for your reply.

Taking off the kick start side allowed me to verify that the clutch adjuster screw was indeed turned all the way in. Also I verified there was only one ball bearing in it, the one I put in there. FYI the hole was dry so if there had been one in there, it might have fallen out without me noticing it when I removed the side cover to begin with. I didn't happen upon it in the garage later where I have been working on the bike.

The clutch cable was and is slack so that is not moving the clutch lifter rod.

My Honda Shop Manual dated 1963 shows 6 clutch and 6 steel plates. It says the clutch friction discs are 2.9 mm (.1148") to 3.0 mm (.1181") and does not distinguish among them. It says to replace if they fall below 2.5 mm (.0984")

For theoretical comparison purposes, assuming the friction discs are originally 3.0 mm (.1181") thick and the steel plates are as I measured them .060" (1.524 mm), the stack thickness would be 27. 14 mm (1.068"). My measured stack thickness was 1.140" (29.96 mm), more by 2.82 mm (.072"), or about the thickness of a steel clutch disc.

I have ordered an extra steel clutch disc and will double up on them somewhere, probably the first one inboard.

I would feel better if I could find one or more thick clutch friction discs so I could swap out one of my thinner friction discs.

Additional insight would be welcomed.
CL72, XL600R, XLV600, TL125, Bultaco Sherpa T 350

skeptic
honda305.com Member
Posts: 16
Joined: Wed Apr 13, 2011 1:34 pm
Location: SoCal

Re: 1964 CL72 Clutch will not engage.

Post by skeptic » Sat May 23, 2020 6:14 pm

I received a new steel clutch plate which measured .0775 thick, which is .0175 thicker than the others. I swapped this for the innermost steel steel clutch plate. I did not double up as I felt that I was running out of room on the outer drum. There is now only approximately .054" between the top of the clutch outer drum and the driven spline of the outermost clutch friction disc.If I were to double up on the steel clutch plates, there would be no allowance for the plates to separate during clutch release and still have the outermost clutch friction disc remain fully engaged in the outer clutch drum. Going to buckle her up and see what happens.

Your thoughts are welcome.
CL72, XL600R, XLV600, TL125, Bultaco Sherpa T 350

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