Topic: 1971 CB750 Clutch not disengaging after sitting

[Johndoa]

Hi,

I picked up a 1971 CB750 that sat for about twenty years and ran fine after I cleaned out the fuel system.  I let it sit for a year and now the clutch doesn't disengage properly.  I takes about twenty tries to get it to shift into gear from neutral.  In a nutshell it shifts the same as if you have the clutch lever pulled in or not.

I've tried the clutch adjustment process per the Honda shop manual to no avail.

My thoughts are that the top portion of the clutch plates dried out and are glued together with some residue, but I don't understand why it will shift fine every now and then.

Does any one have any thoughts, experience or solutions to this problem.

Also, does any one have recommendations for clutches, preferably ones I could use synthetic oil with.

Thanks for any of input.

Last edit:  I have a Suzuki GS850G that does the same thing and yes the Suzuku is for sale.

[goldarrow]

With engine off, put in 5th gear and walk the bike around your neighborhood

[flybox1]

Easy for that cork to delaminate.  Using it probably helped. 
Time to open it up.

[Stev-o]

Easy for that cork to delaminate.  Using it probably helped. 
Time to open it up.

Or the discs are sticking together.
Open it up.

[2wheels]

This happened to me too.  At it's worst I would drive around the yard with the clutch lever pulled in until it let go.  I would do a rolling start to get the bike moving.
This happen to me before the internet existed so I was trouble shooting on my own.

I just replaced the fiber clutch plates with new ones from Honda and this fixed the problem.
edit - I should have added that this went on for a year before I changed the plates.  I think once it starts it does not get better.

[trueblue]

My bike sat since the mid 80s. When I got it and got it running a couple of years ago the clutch was stuck. I started the bike, pushed it up to jogging pace, jumped on and snicked it into first. Then I rode around in first with the clutch pulled in and my foot on the rear brake all the while accelerating an backing off until it released. It took a bit of riding to come 100%  but 5000 miles later it is still going strong.

[PeWe]

Same with my bike. It must be the newer oil when I cannot recall anything similar from the 80's when I used it before the long +20 years coma , then in pieces and 2 years putting it together.

I have to sit on bike, gear to 2:nd gear, clutch lever pressed, rock the bike forward-backward a few times and clutch will disengage. My clutch fiber plates are new. I hope the latest oil with plenty of zinc will make the clutch to work better after some driving.

[strynboen]

mine got lock up after 14 days.

..so dont open the engine..just take drive it good hot..and pull chlutch and give full speed in 2 gear..and it breakes easy free...

[Johndoa]

I had my fist day off in fourteen days so I decided to work on my bike.

I started the bike and let it run for ten minutes to warm up the oil, but when I took the clutch cover off, I noticed there were trace amount and of oil.  None of the clutch plates where stuck together, they spun freely and all had a coat of oil on them.  I'm leaning toward the idea of oil flow causing the problem.

Since I had the clutch assembly apart I installed new fiber plates, steel plates, and heavy duty springs I purchased from CycleX.

After changing the oil with expensive Mobile 1 motorcycle oil for wet clutches I still have the same problem and two new ones.

1) I cracked the oil pan over tightening the drain plug.  If any one has one for sale I'm in the market to buy one.

2) When the clutch cable is pulled in the cable doesn't return to it's initial position.  I changed the oil seal for the throwout so I'm not sure if its the new seal or something that is binding.

I'm not sure how to proceed trying to fix the oil flow issue or if it is even a oil flow issue.  The bike sat for a while so almost all of the oil drained into the engine.  When I started it for the first time after sitting, the oil tank filled up to the normal level, so I know the oil pump is working.

[Don R]

Could the clutch lifter be broken or way out of adjustment?

[Ace]

I had a similar problem. Bought new friction plates which fixed the problem.

[martin99]

I had my fist day off in fourteen days so I decided to work on my bike.

I started the bike and let it run for ten minutes to warm up the oil, but when I took the clutch cover off, I noticed there were trace amount and of oil.  None of the clutch plates where stuck together, they spun freely and all had a coat of oil on them.  I'm leaning toward the idea of oil flow causing the problem.

Since I had the clutch assembly apart I installed new fiber plates, steel plates, and heavy duty springs I purchased from CycleX.

Why would you do this without trying to investigate the problem? Did you soak those new fibre plates in oil before you fitted them? Need to be soaking for a good few hours, preferably overnight. If not, they can swell after adjustment and lock the clutch so you'll be no further forward in trying to diagnose your problem.

1) I cracked the oil pan over tightening the drain plug.  If any one has one for sale I'm in the market to buy one.

That sucks, sorry to hear that, but this is your priority now. Maybe a temp fix with JB Weld? Try a search to see what others have done.

2) When the clutch cable is pulled in the cable doesn't return to it's initial position.  I changed the oil seal for the throwout so I'm not sure if its the new seal or something that is binding.

I'm having a hard time trying to understand this bit, can't imagine what oil seal you mean. If you mean the paper gasket, it's unlikely to be having any effect on the cable. Sounds like an adjustment problem to me, or you have made an error fitting the new parts.

[Johndoa]

I had my fist day off in fourteen days so I decided to work on my bike.

I started the bike and let it run for ten minutes to warm up the oil, but when I took the clutch cover off, I noticed there were trace amount and of oil.  None of the clutch plates where stuck together, they spun freely and all had a coat of oil on them.  I'm leaning toward the idea of oil flow causing the problem.

Since I had the clutch assembly apart I installed new fiber plates, steel plates, and heavy duty springs I purchased from CycleX.

Why would you do this without trying to investigate the problem? Did you soak those new fibre plates in oil before you fitted them? Need to be soaking for a good few hours, preferably overnight. If not, they can swell after adjustment and lock the clutch so you'll be no further forward in trying to diagnose your problem.

1) I cracked the oil pan over tightening the drain plug.  If any one has one for sale I'm in the market to buy one.

That sucks, sorry to hear that, but this is your priority now. Maybe a temp fix with JB Weld? Try a search to see what others have done.

2) When the clutch cable is pulled in the cable doesn't return to it's initial position.  I changed the oil seal for the throwout so I'm not sure if its the new seal or something that is binding.

I'm having a hard time trying to understand this bit, can't imagine what oil seal you mean. If you mean the paper gasket, it's unlikely to be having any effect on the cable. Sounds like an adjustment problem to me, or you have made an error fitting the new parts.

I don't have much free time so I ordered the new clutch parts a while ago just incase they where needed and the fact the clutch in the bike is was at least two decades old. 

I didn't just throw the new fiber plates in they where soaked in new oil for about 24 hours.

No I don't mean the paper gasket.  There are oil seals that go around the shaft of the kickstarter and the shaft of the throwout lever.

And yes, I am going to try using JB Weld on the oil pan.

[CB_Jeff]

I had a similar problem with my K6.  What I did was warm the bike up in neutral and then (on the center stand) put it in gear and let it spin the rear wheel for a while, then back to neutral for a bit, then into second and then back to neutral and then shut it off.... probably running the engine for three to five minutes total.  Then shut it off.  Then using a bungee or piece of rope I pulled in the cluch lever and secured it in the "pulled" position and let it sit over night.  Worked well for me.  I think the key is warming up the engine / oil and then leaving the spring compressed overnight.  Maybe it will work for you?  Won't cost anything to give it a try.

[martin99]

Johndoa, sorry if my reply sounded short, just trying to help. Is the cable in good condition? Strange that it doesn't return like it should

If you are confident that you have installed the clutch correctly I'm still leaning toward an adjustment issue.

[Johndoa]

Had a few hours tonight to take the side cover off and look at the clutch and lever mechanism that compresses the spring allowing the clutch to separate. 

I found out the problem was I'm an idiot.  The clutch was fine, the lever adjustment was fine, and everything in the case was as functioning properly.  It was lack of tension in the clutch cable.  Apparently I don't know how the feel the clutch spings through the clutch lever.

I'm glad I didn't drive this around in gear hoping to break the plates apart like I originally thought was the problem.  That could have been really painfull.

[Ace]

As you mentioned, it could have been worse. Good to hear you found the problem. Live and learn.

[2wheels]

Had a few hours tonight to take the side cover off and look at the clutch and lever mechanism that compresses the spring allowing the clutch to separate. 

I found out the problem was I'm an idiot.  The clutch was fine, the lever adjustment was fine, and everything in the case was as functioning properly.  It was lack of tension in the clutch cable.  Apparently I don't know how the feel the clutch spings through the clutch lever.

I'm glad I didn't drive this around in gear hoping to break the plates apart like I originally thought was the problem.  That could have been really painfull.

I guess no one asked the question "does the clutch operate normally once you get it free"   Your answer would have been "it never gets free"  Two very different problems.  Glad it is fixed.

Show me a picture of the GS850 if you can.

[lucky]

When the bike sits for a long period of them the clutch fiber plates and metal plates can get glued together.
Even if you get it to run and drive some of the plates can be stuck.
Also if you remove the plates you will see that part of the plates were sitting in oil and the other half got dried out.
Best solution is to replace the clutch plates.

On the 77-78 CB750's you will see that the clutch pack is divided in the middle of the stack by a special plate. Often the outer plates will be fine, but the inner plates are stuck together.

[MCRider]

I don't see how any of the plates can be "sitting in oil". IS the oil level really that high in a dry sump engine? Even if it has wet-sumped? Certainly the lower part of the plate will stain as the plate dries out top to bottom.

Nevertheless, it is true the plates will stick over time.  If one does take the plates out to refresh or replace, consider Mark "HondMans" trick of drilling out the hub to let more oil into the clutch pack strategically. Seems to have really helped mine. Smooth shifting, full disengage when pulled in.

[PeWe]

Latest oil change in my bike was an improvement regarding dragging clutch. The old Catrol 4T oil was almost new, max 400km.
Now Red Line motorcycle oil.