'70 CT70 Automatic Clutch

OLD CT

OLD CT

Well-Known Member
I have a feeling this time it will work. I always throw out the old discs at clutch service time and they never look worn with any new to me ct70.

You will never need to replace them for a looong time using the proper jaso M/C wet clutch oil. Just spinner cleanings in the future.
 
6

69ST

Well-Known Member
It's easy to forget that we are dealing with 50-year-old machinery. The parts support is friggen amazing...to the point where we take it for granted.
 
R

RePete

Member
Good Morning All.
The new Clutch Friction Discs arrived last Friday and I dove into the replacement as soon as I was able during the weekend.
A measured level of success accomplished! :)
Old Ct & racerx... both of you were correct! Although the discs looked and measured fine they were 50yrs old and as much as I'd like to understand how their age would affect their performance causing them to not work properly (being that they were within spec and visually fine) I've come around to just accepting it. Should've just replaced them the first time I opened it all up for cleaning.
I used the term "measured success" for this reason. The bike has not been road tested yet. It's on the lift with real wheel raised. So how do I know it's working? Because prior to replacing the Friction Discs the bike would fail to operate properly under the same conditions. After a good warm up (10 mins +/-) the rear wheel could not be stopped with the bike in gear without continued clutch grabbing and then stalling. That's not the case now. Nearly 40 continuous minutes of run time through all the gears and varying rpm's and it'll idle in gear every time. I'm about as sure as one can be that the issue is resolved.
I'll loop it around the neighborhood maybe tomorrow night as the final test but given my size I'm staying off of it as much as possible.
After running it Saturday I didn't turn the fuel valve off and later discovered an overflowing carburetor. So right now it's on the bench so I can adjust the float level.

RePete.
 
6

69ST

Well-Known Member
RePete said:
Although the discs looked and measured fine they were 50yrs old and as much as I'd like to understand how their age would affect their performance causing them to not work properly (being that they were within spec and visually fine) I've come around to just accepting it.
Click to expand...
Thickness, like most quantitative specs, can only tell you so much. Ostensibly, it'll tell you how much wear has occurred. What it won't reveal: evenness, symmetry, distribution or pattern of any wear, swelling of clutch friction material, changes in the properties of clutch friction material. These clutches are really more like the clutch packs in automatic transmissions and friction characteristics involve some complicated science & engineering. Suffice it to say that a half century is more than enough time for clutch friction material to change. Oil exposure, alone, might be sufficient to alter the binders used to hold the friction material together, allowing it to soften or swell. Since it's engine oil, the same acidic compounds that can cause engine damage could wreak havoc on the friction linings. Considering the low cost of new discs and how easily they can be replaced, that's about all the technical discussion we need. Consider what happens to 50 year old brake shoes on these same bikes...the friction linings can delaminate, no oil exposure involved. Non-metallic parts tend to have finite lifespans.
 
Tripod

Tripod

Well-Known Member
Bottom line is alot can happen in 50 years. Whether its from wear or from previous owners, it comes down to balancing cost and or originality versus starting with a known.
 
6

69ST

Well-Known Member
Tripod said:
Bottom line is alot can happen in 50 years. Whether its from wear or from previous owners, it comes down to balancing cost and or originality versus starting with a known.
Click to expand...
I agree...except as it pertains to safety and operational items, not much choice there if you want to ride.
 
R

RePete

Member
Hi Fellas -
My plan is to give it test ride out in a safe grassy area this coming weekend where speed is limited. The tires were not replaced whereas I did all of this for two reasons only.
Reason 1: Down the road when it's time to start tearing the bike apart and investing in new /replacement parts, paint, chrome. etc. I wanted to have a good idea of what I'd be dealing with concerning the motor, which is all I really cared about. So I wanted to get to a point where it either ran well or displayed symptoms indicative of needing a rebuild. It has very low miles on it, but the overall care of the bike was poor. Concerning the motor, so far, so good. It's looking like it may (eventually) just require a complete exterior cleaning/detailing/paint.
Reason 2: My Daughter... She walked into my garage and exclaimed "that is sooo cute - I want to ride it". Naturally, that's when I dragged it home and didn't even know if I could make it run at all. But given her enthusiastic interest, it went up on the lift and has been residing there since.
With the help of you gentleman talking me through an unfamiliar machine and redirection on a couple of obvious oversights on my part due to my own lack of concentration all appearances are that the journey will be a success.
We'll know more once it's actually ridden this coming weekend.

RePete
 
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R

RePete

Member
Final Update (pre weekend):
Although I had anticipated not ride testing the little CT till the weekend, last night upon returning home I never made it past the garage.
I did a final adjustment to the carburetor float and after reinstalling and some fine tuning adjustments while on the lift I decided to ride the bike myself (shortly) through the neighborhood alleyways. :yellow70:
It operated perfectly!!!! What a difference those new Friction Discs made! I thought my only issue was the clutch grabbing but the difference in performance is very noticeable. I was surprised at how well that little bike hauled my 250lb butt.
Just perfect (aesthetically not so much :eek:). Motor runs great. Smooth idle, acceleration and deceleration. Up shifts and down shits as it should. As noted, clutch issues resolved and bike will idle in gear as needed.
This little guy is a HOOT!!!
It runs so well that instead of just storing it away for future restoration I'm going to replace a few needed items and keep it in a ride-able state until I'm ready for it.
I bought a valve tappet adjusting kit (useful for this and my Yamaha XS650) and will take care of those shortly.
After that, mechanically speaking there's nothing left to do. Just address some wear items (tires, grips, etc.), straighten out the electrical (there's currently no switch, rectifier or battery) and start collecting replacement parts for items I know won't be reconditioned/re-plated/etc.

A BIG thank you to all and especially to racerx, OldCT, Tripod, cjpayne and Kirrrby. Hope I didn't leave anyone out.
Your thoughts through my hands! :D

RePete
 
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