Clutch suddenly not working

[JimF]

The bike with the problem is a 1965 250 narrow-case.

I recently replaced the clutch cable after the old one broke. Following that and for a few days afterward all was fine.

Yesterday I rode the bike to work and back (about 16 miles) with no issues.

This morning I started the bike (no problems there) but when I pulled in the clutch and dropped into 1st, the bike lunged forward and died. I tried again, being certain I had the clutch engaged. I felt the clutch spring tension in the clutch lever, I dropped it in gear and again it lunged and died.

With the clutch pulled in I tried rocking the bike to separate the plates but had no luck and I parked the bike and took the car.

This bike has never had a problem with sticky clutch plates, not even on the first start after winter.

Tonight I took the engine cover off and looked at the clutch. I pull in the lever and I can see the friction plates move though some separate before others. I can't be sure what the steel plates are doing.

While holding the clutch and visually seeing gaps occurring between the plates, I rotate the rear tire and I find the transmission is still engaged to the engine.

I haven't taken the clutch basked apart yet, I am thinking that is my next step so as to examine the steel plates.

I use straight 40-weight non-synthetic racing oil in the engine.

Any advice about what this could be will be appreciated.

Jim F

[Jordan]

The sudden onset of a stuck clutch does sound mysterious.
All I can say is that it is possible that a clutch feels normal when operating the handlebar lever, yet the plates can be stuck together.

[motoital]

Have you tried using the kickstater with the clutch engaged? My plates would stick from time to time and that trick usually freed the plates up.

[double diamond]

Jim,
If your clutch plates are indeed disengaging, the clutch needs to come apart. Something has locked the clutch hub to the basket or the clutch basket to the input shaft. If there isn't schrapnel inside the clutch, one of the clutch basket bearings may have failed or something else that has locked the clutch basket to the input shaft. Matt

[Bevel bob]

The new cable may have slipped a bit in the solderless nipple under the cover, these do settle down ,and as its the last thing you did its usually worth checking that first. Also the clutch center nut can come loose if you have that feeble std lockwasher.

[JimF]

The clutch basket nut is tight, I have the left side cover off and checked it.

My guess is the cable didn't slip as the clutch lever has the same minimal amount of free play as it had before. Also I can see from the movement of the clutch basked plates that the cable is connected.

This weekend I will take the right side cover off and disconnect the clutch cable, then I can take the clutch plates out and examine them.

Matt, I hope you are wrong but I fear you are right. There is either something stuck in the plates but what that would be I couldn't begin to guess, or as you say there is something like bad bearings or locking it all together.

Thanks for the good advice everyone. I will report back with my next findings.

Jim

[Nick]

Probably the oil. No need to run glue like that in a roller-bearing engine, try 20/50 motorcycle oil.

[JimF]

Tonight I took the left side cover off and everything looked clean. There were no shards of metal in the oil that drained out from the cover. That was not a surprise as I had been under this cover a day or two ago.

I released the nut on the clutch actuation rod, backed it out and then I took out all the springs.

I began to pull the out the friction discs and plates, most of them coming out en masse, bound together by the surface tension of the oil on them.

I kept waiting to find shards of metal, or some kind of sign of extreme heat damage, but as I finally got to the last plate and there was absolutely nothing amiss.

I could spin the center hub of the clutch freely and since I had left the engine in gear after having tried to rock the plates free the rear wheel spun with the club. There were no grinding sounds, the engine was not engaged, nothing.

After I came up blank as I tried to figure out what might be wrong I started wiping off the plates and re-stacking the clutch pack back into the bike. All the plates looked good but just when I was a few plates from the outermost end of the pack I picked up a friction plate and drive plate that were stuck together. But this was no simple bit of surface tension as these two plates were really stuck to each other. I could not pry them apart with my fingers. I had to force them apart with a screwdriver, being careful not to damage either plate.

On the plate was a very slight amount of some kind of residue. It was a bit bumpy to the touch, but it was rather sparse and just barely had any real height to it. I'd be surprised if the residue was more than a thousandth of an inch thick.

I tried to wipe it off but it wouldn't budge, so I went to my parts cabinet and sifted through some old clutch plates to find a clean one.

I put the clutch all back together and tested the lever pull and the clutch was back to working again.

I have to say that I had really rocked the bike in gear to try and free any stuck plates, to the point where I was really worried I was going to wreck something if I tried any harder. When I think back about it, there almost must have been a great amount of instantaneous torque that the engine put on the clutch pack when this problem arose, that is to say the couple of times when I dropped the transmission into first with the engine running had also failed to free up the plates.

I'm pretty happy that this was such a minor problem and that I didn't have a major failure.

Thanks for all the good advice and support.

Jim

[Nick]

So, did you change the oil?

A long time ago, when I got my first Triumph, I asked Gary Bray, a tuner who'd built some of the fastest BSA Gold Stars, what oil I should run in it. "Straight 40 or 50 weight!" he said with conviction. So that's what I did. Only later did I realize that he'd done so because that was the oil that had worked so well on those old bushing motors he built.

That Triumph today: (And yes, we run straight 50wt in that bushing motor behind it!)

[Jordan]

The Triumph Daytona 500 was a lovely bike. Smaller and lighter than a 650, still a peppy performer.
No crankshaft bushes in those I think, although the single carb versions used a bush.