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What causes a hot clutch to go grabby?

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What causes a hot clutch to go grabby?
Started at 04:46pm on the 15th December, 2018 by stinkwheel
stinkwheel Subject: What causes a hot clutch to go grabby?
Since I will shortly have two road-going bullets, I'm giving some serious consideration to converting my old faithfull 350 into a classic trials machine on the cheap (as in for doing a classic reliability type trial rather than riding over boulders on a classic bike).

The one thing putting me off is the clutch and its likleyhood of surviving a stupid hill restart. Even as it is, when it gets hot it tends to get grabbier and grabbier. I can see me being the subject of an humerous youtube video halfway up some godforsaken muddy hill in driving sleet, stalling the thing on a stop/start, having to kickstart it on a 5 in 1 slope then being unable to get a gear (this pretty much happened when I went for a ride along with a local vintage tractor run with my trailer on last summer).

Thing is, people DO do trials on bullets (even the riding over boulders sort) so it got me thinking about what I should look at doing with the clutch and I suppose the first part of that is thinking about WHY it gets grabby when hot. The lever comes closer and closer to the handlebars.

So the pushrod, that'll make it stiff if it expands through heat but shouldn't that make it slip, not grab? I can fit a ceramic ball bearing in the rod to reduce heat transmission in any case.

So are the plates expanding or what? One thought I had was to use a different lever with a longer "swing" to get larger seperation of the plates. It turns out, a GPZ500 clutch assembly with the adjuster screw removed bolts right on a bullet with the standard cable.

I know the ultimate solution is to get a Newby clutch but that's really the nuclear option, If I'm getting one of those, it'll be going on the 612! I'd rather do some sensible engineering solutions to the existing clutch. This then leaves the option of carrying a spare set of plates from my bucket full of part-worn bullet clutch plates on a trial without needing a second mortgage.
Posted: 04:46pm 15th December, 2018
papasmurf Subject: What causes a hot clutch to go grabby?
How old is your old 350. There are plenty of upgrade clutch parts in our hosts catalogue.
Posted: 05:00pm 15th December, 2018
stinkwheel Subject: What causes a hot clutch to go grabby?
Pretty new, I call it "old" because it had a hard paper round. It's a 2007 with a 4-plate clutch fitted.

There are many things you can buy. I suspect most of them would do nothing useful to prevent a hot clutch grabbing. They mostly seem aimed at preventing clutch slip.
Posted: 05:19pm 15th December, 2018
Leon Novello Subject: What causes a hot clutch to go grabby?
Speaking from experience, using a cheap oil will turn it into a type of lacquer at very high temperatures, which will stick the plates together. Use Automatic Transmission Fluid, it can stand higher temperatures. I have posted this a couple of times in the past.
http://www.snowvalley.20m.com/bikes/clutches.htm
Posted: 08:09pm 15th December, 2018
Norm Subject: What causes a hot clutch to go grabby?
I have never found a genuine fix, trust me I tried every trick I could think of, too many flaws in the design, not allowing enough lift on the plates. I have 9 springs in my Inter clutch and to get it to work I have to adjust it up when I get into traffic, and back it off when not in traffic and it still slips, so I just back off when it slips. I fitted a few Newbys and they solve the problem
Posted: 08:53pm 15th December, 2018
Aethelric Subject: What causes a hot clutch to go grabby?
My clutch (2004 sixty-5) was a bit sticky. It was much worse with a hot engine. I adjusted everything to no avail. Then I looked closely at the handlebar lever. It looked fine but the END of the lever touched the bar at max travel. I heated the lever and bent it a tad. To the eye it looks just the same, but now the MIDDLE of the lever hits the bar first so there is a little more travel. This has helped no-end. Still not perfect though, a bit more travel would help.
In the mean time I notice that the slack in the cable increases as the engine warmsj. Until I sort it, I take some slack out of the cable with the handlebar adjustment after the engine has warmed up a bit. I let it out again when the engine is cold - i.e. before I set out on a ride again.
I don't know about yours but a lever with more travel would sort mine. I'll do a bit mote metalwork on it over the winter.
Just a thought, have you got thick chunky handgrips fitted? They would reduce travel.
Posted: 10:21pm 15th December, 2018
John M Subject: What causes a hot clutch to go grabby?
I have a 1965 Bullet engine in my classic trials / greenlane bike and do not have any problems with the clutch. I don't do the tricky riding over boulders type trial so the clutch doesn't get too much stick.
I use cheap and cheerful Indian clutch plates and the rest is a bog standard 62 year old RE clutch, although it only has three clutch springs rather than the usual six.
I think all Enfield clutches get hot and bothered if you stay in gear too long when stationary, such as traffic lights, but the stop and re-starts on classic trials are only brief affairs and are not likely to upset the clutch.
Posted: 11:29pm 15th December, 2018
Leon Novello Subject: What causes a hot clutch to go grabby?
Aethelric: As stated above; replace the steel ball with a ceramic ball between the rods, this will lessen the expansion and contraction of the rods and might help with your constant adjustments when the things get hot and cold.
Posted: 07:28am 16th December, 2018
John M Subject: What causes a hot clutch to go grabby?
If you are still on standard road gearing, you may be over using the clutch off road causing it to get hot and drag etc.
Posted: 08:49am 16th December, 2018
scotty Subject: What causes a hot clutch to go grabby?
Use the neutralselector lever as you slow down, no more sitting in 1st with the clutch getting hot, that is what its there for.
Posted: 09:50am 16th December, 2018
Wheaters Subject: What causes a hot clutch to go grabby?
The clutch on my 2004 350 (Iron engine) Electra is as sweet as a nut. I wonder if yours might have a warped plate, or one that warps as it heats up - it's possible that replacing the plates might fix the problem. Or, removing them and flatting down both sides of the steel ones on a sheet of wet and dry might help. I also followed the Hitchcock's advice and use ATF in the primary chaincase, btw. I've found using the neutral finder to be very tricky - difficult to get my boot on it even when I can look directly at it, let alone when trying to find it by feel when concentrating on the road. So did one of my uncles many years ago - he ended up falling off his RE and losing half of his right foot when he got it wrong, he always blamed the neutral finder. To the best of my knowledge, he never rode a bike again.
Posted: 11:38am 16th December, 2018
Norm Subject: What causes a hot clutch to go grabby?
If somebody comes up with a proper fix to this problem I would be interested, so far I haven't read anything
Posted: 06:39pm 16th December, 2018
Norm Subject: What causes a hot clutch to go grabby?
Just as a bit of info on what I worked out many years ago. From memory the travel on the cable at the handelbar is 15/17mm with a standard lever setup. For every 5mm of cable travel on an Albion box, this equates to .4mm of rod travel. 15/17 divided by 5 = 3. 3 x .4mm equals to 1.2mm of rod travel to release the plates. This is more than adequate when everything is cold. Then you have to factor in the expansion rate of the aluminium gearbox housing and the expansion rate of the steel rod and the box expansion is greater so therefore your 1.2mm of lift on the plates has been reduced to probably half that and this then means the plates start to drag, this then heats the plates up further and this causes the drag to increase til you reach the point where there is no way of disengaging the clutch to a point where the only way to stop is switch it off or stall the motor which is what you usually have to do because by this stage you have your left hand dragging on the clutch lever to no avail and your right hand flat out holding the front brake. The only genuine solution I found was to buy a Honda
Posted: 07:50pm 16th December, 2018
Adrian Subject: What causes a hot clutch to go grabby?
No aftermarket for cast-iron gearbox casings then, Norm? ;o)

A.
Posted: 08:36pm 16th December, 2018
John L Subject: What causes a hot clutch to go grabby?
stinkwheel - When you say your hot clutch "grabs, or becomes "grabbier", I think you mean it starts to drag ? (Evidenced by ever-increasing slack on the cable?) Well, any long-time Enfield owner will tell you that they all do that......... The problem is lack of pushrod travel (hot OR cold) for various possible reasons combined with plates that are badly affected by heat.
Why do you think Enfield fitted a neutral finder - as standard equipment ?
My experience mirrors Norm!s...... and the only contributor here that I can recall ever claimed to have found a complete and lasting cure for this affliction was "Simon", who advocated cork-lined plates, I believe.
You can ignore all the twaddle about rod expansion and ceramic balls, anyway..........
Posted: 09:44pm 16th December, 2018
Leon Novello Subject: What causes a hot clutch to go grabby?
My nightmare experience, like Norm`s, on a hot Summer day, having to slowly approach traffic lights till they turned green, because I couldn`t change gears if I stopped. When I got home, nearly riding through the garage wall, having to stall the engine. The clutch plates were fused together, I had to lever them apart with a screw driver, this was the result of using cheap lawnmower engine oil. Only ATF-Type F for Fords after that. The clutch lever movement stayed fairly constant with a ceramic ball too. I had thoughts of fitting a larger ball to get a bit more rod movement, but never got around to it.
Posted: 10:19pm 16th December, 2018
Norm Subject: What causes a hot clutch to go grabby?
Leon the ceramic ball would make things worse,you need the rod to heat up more to grow in length. I had considered moving the cable entry point in the end cover further forward and shorten the clutch lever (71) This then would increase the travel on the rod but would also make the clutch heavier to operate. Sure it might have fixed mine but it was too difficult to make up something for other people to be able to modify for their bike so I just gave up
Posted: 10:52pm 16th December, 2018
Mark M Subject: What causes a hot clutch to go grabby?
Stinkwheel. can you explain about the Kawasaki GPZ550 clutch please? I Googled pictures of it and I can't see how any of it would fit, for instance the outer plate is for a 5 spring arrangement which wouldn't line up with the 3 spring posts on an Enfield one?

REgards, Mark
Posted: 10:56pm 16th December, 2018
vince Subject: What causes a hot clutch to go grabby?
Hi, check that there is no end float on the mainshaft caused by loose lefthanded nut and the clutch is tight on shaft. Also fill the pushrod tunnel with light grease, pushrods are usually red with rust. Tighten up the cable adjuster until there is no slack. Take the bike for a ride at low speed in top gear and see if you get any slip when putting the power on up a gradient. If it slip then back off adjuster just enough to grip. Vince
Posted: 10:58pm 16th December, 2018
Norm Subject: What causes a hot clutch to go grabby?
The other thing that helps is the outer cover stiffening bolt mod on the Indian covers, this can gain you another .5mm on the rod and a heavy duty clutch cable, one you get made up using the cable they used on the big Jap 4 cylinder bikes, not the off the shelf stuff. I even extended the pivot point on my handelbar lever to get me a little extra cable travel, cable travel is now at 20mm. That increase gave me about .3mm at the rod. It all helps slightly, a fraction of a mm here and there but no matter what you do it will always be a borderline clutch
Posted: 09:02am 17th December, 2018

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