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Restored CT1 but clutch is slipping

  • Bbd83
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So a buddy and I just finished a complete frame up on a 70' CT1 that had been started and never finished by a fella that passed in an unfortunate motorcycle accident.

It turned out beautifully but it hasn't been enjoyed yet as after the first ride we quickly realized the clutch was slipping. It happens the worst when under higher revs. The bike isn't rideable as is.

I started with clutch adjustment but after taking off the left cover under the "bump" I realized that after the locknut was broke free the flathead adjuster wouldn't move freely to adjust. It seems stuck, tried to use some penetrant but no help. I did a couple adjustments (more and less freeplay) at the clutch lever to no avail. Also with the cover off, the pushrod is there but when I push (hard) on it it doesn't budge. Should it? We wanna exhaust everything on the left side before digging in to the basket side.

Any help appreciated. Quite the shame to have a fully restored bike you can't even ride. 
09 Jun 2022 22:33 #1

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Replied by Gr8uncleal on topic Restored CT1 but clutch is slipping

Did you use engine (gearbox) oil suitable for wet clutches? Normal engine oil will cause clutch slip.
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09 Jun 2022 23:40 #2

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Replied by RT325 on topic Restored CT1 but clutch is slipping

Chances are you'll need to replace the fibre plates & also leave out the 5 rubber spreaders if they're still present. When you get the adjuster lock nut free just give the pushrod a little clearance & hold it from moving as you nip up the lock nut. Might have to get inventive to block the arm to free the nut. Also NO you won't be able to push the pushrod by hand. There's a lot of pressure exerted by the mechanism via the cable & lever. Be interesting to know how much in some measurement of pull at the lever. I just use 15/40 or 20/50 engine oil for older cars. 10/30 would be better & had that at work [yep I worked once lol]. ATF has been mentioned & could be good even though pretty thin but is for older automatics which just have stacks of clutches with plates like your Yamaha. Reminds me of my "68 Rover V8 which I drove so hard the linings fell off the drive plates & more recently similar happened to my old V8 Audi Quattro, bloody nightmare to fix haha. Sorry, wondered off the CT1 story. My AT1--175 top end slips too, so should fix it. Here's my ratbike if the link works & you can sort of hear it slip up in the revs but gets better when hot so maybe ATF thinner oil might help. But bottom line 'is' needs new plates.

Last edit: 10 Jun 2022 01:06 by RT325.
10 Jun 2022 01:04 #3

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Replied by MarkT on topic Restored CT1 but clutch is slipping

Yes, you must make sure there is a little freeplay between the cover adjuster and the pushrod sticking out of engine.

And, no, you should not be able to push the pushod by hand unless maybe you're superman. 
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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10 Jun 2022 03:34 #4

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Replied by Tom P on topic Restored CT1 but clutch is slipping

As the others said, no way you could push that rod with your hand. You're pushing against five strong springs. Just months ago I got an old 1971 CT-1 running,. It had the original friction plates, and they were shot, only having 340 miles on it. The clutch springs were also under spec, which should measure 31.5 mm. They say if they measure 1 mm under that, replace them.

As folks here suggested, I replaced the friction discs, leaving the rubber rings out, replaced the springs, and it's working perfectly.

Here's a link to the springs I used (you need five), and I'll post a picture of the eBay friction plates I bought. They shipped really fast, and have a warehouse in Southern California,, and the southeast.

hvccycle.net/yamaha-clutch-spring-90501-...-or-137-16333-00-00/

 
10 Jun 2022 07:32 #5

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  • Bbd83
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Replied by Bbd83 on topic Restored CT1 but clutch is slipping

The bike has Yamalube 10-40 in it now. We'll start by trying to get that adjuster free'd up and then move to the right side. Disassemble clutch and measure the plates and springs. Appreciate the quick replies! 

 
10 Jun 2022 08:07 #6

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Replied by Bbd83 on topic Restored CT1 but clutch is slipping

I've heard of leaving the rubber rings out but for knowledge sake what was their intended purpose and why leave them out?

 
10 Jun 2022 17:31 #7

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Replied by JayB on topic Restored CT1 but clutch is slipping

I believe the rubber rings help the clutch plates separate when you pull in the clutch.  They also reduce clutch dragging.  Later Yamaha clutches get rid of the rubbers and just use a spring between two of the plates.
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Last edit: 10 Jun 2022 17:47 by JayB. Reason: spelled out a preposition
10 Jun 2022 17:46 #8

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Replied by Bbd83 on topic Restored CT1 but clutch is slipping

Just to update this thread, we took the basket apart and all the friction discs were like new, above 4mm, plates were nice too, springs we're about .5mm under spec. Removed rubber rings. Everything looked good so we filled it to spec with Yamalube and also got the adjuster free to get proper adjustment. Bike was way better to ride but not quite perfect. Still a slight slip here and there usually under high rev. Could it be that the plates need to be worn in a bit as they looked new?

Also that little ball, will it fall out the left side or the right, possible it got lost while shuffling the motor around and what's its purpose?

 
29 Jun 2022 10:49 #9

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Replied by Tom P on topic Restored CT1 but clutch is slipping

I believe the little ball makes it easier for the shafts to rotate, as opposed to having the two shaft end pieces up against each other. Also spaces it out correctly.

When you measured the friction plates, did you measure from the inside? When the steel plates wear them it leaves a rim around the outer edge of the friction plate that might still measure 4mm, even though under that rim it might be 3.6mm or less.
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29 Jun 2022 11:43 #10

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