Why are our clutches so troublesome, a theory.

kevski

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I am on my second XS650 and have the same clutch woes as on my first, dragging and almost impossible to get into neutral while standing still, it's all fairly well on start up but when warm it's a pain, i have replaced everything except the mushroom and basket, the basket is as good as new so we can discount that the mushroom has a little dimple where the ball bearing pushes it slightly off centre, it is also a little to small in diameter for the hole in the shaft both of which show no signs of wear, because of this when the clutch is operated the mushroom shaft goes offset in the shaft thereby when clutch separates it does not do it squarely leaving one side just touching causing the drag (theory), had the mushroom a much larger contact patch and better fitting shaft like on my KZ1000 mushroom it would open more squarely, the six plate is better as it has the conical spring instead of a seventh plate, this helps to push the plates away, now i am going to work on a modification and experiment using an engine valve with the same stem diameter, providing the mushroom part is compatible, and a shorter push rod, the longer stem on the valve will minimise offset, naturaly the valve head will have to be trimmed and the face polished, lets have some thoughts on this guys.
 
On my internally stock 650D, the clutch actually works fine. I replaced the 7 friction plates when I bought it, also replaced pushrod seal and bushing, and replaced the pushrod with an aftermarket single piece one, otherwise it is stock. No slipping (mostly due to limited hp I guess...), and no dragging either. Selecting neutral at a standstill is not difficult at all. My RD350A has a very similar clutch design, and is equally trouble free.
I guess with a hotter, big bore engine, it may slip. The cure for that would then be a higher ratio primary gear set, combined with an 8 plate stack. Stiffer springs should be a last resort IMHO.
 
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My 81 had 3680 miles on it when it was parked in 1986. I brought it back in 2018 and once it had the proper
oil and a clutch adjustment while hot it was fine. No slipping or dragging and with the long throw shifter I can
hit neutral rolling or stopped without any problem. I just broke 6000 miles on it.
 
There is no slip, just drag and the neutral selection when static, semi synth oil, I raised this point as the KZ clutch is the same system of operation and it's never a problem just a much closer tolerance of component parts and after some thoughts on a possible mod.
 
kevski, your theory might be sound. However, I have had dozens of XS650s pass through my hands, mostly resurrections, and I have never had any of the clutch issues that are so commonly mentioned. The basics have been stated countless times, but here they are again: everything adjusted and lubed, brand-new Motion-Pro cable, and cable must be routed as smoothly as possible, no tight bends, and minimize number of bends -- very important. To this I will add that I always use the two-piece clutch rod. Yamaha replaced the one-piece with the two-piece, so they clearly thought it was an improvement. Yes, the two-piece is harder on the bushing, however it was engineered to match the expansion of the engine as it gets hot -- one piece is aluminum, the other piece is steel -- and that's your stated problem. Lots of people are able to get the stock clutch to work. Before I tried your experiments I would do the basics that I mentioned and put a two-piece push rod in.
 
I thought of trying to make a longer mushroom part from an old engine valve so that I could combine it with a 10mm shorter alloy pushrod from another Yamaha model (XS360/400/500). I thought this might address the different expansion rates we encounter between the steel pushrod and alloy cases. The XS360/400/500 pushrod is also a little "fatter" than the 650 ones (8.6-8.7mm vs just under 8mm) so would need to be turned down some.

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If you do go ahead and make a new mushroom, this pushrod may be the perfect companion for it.
 
I have had dozens of XS650s pass through my hands, mostly resurrections, and I have never had any of the clutch issues that are so commonly mentioned. The basics have been stated countless times, but here they are again: everything adjusted and lubed, brand-new Motion-Pro cable, and cable must be routed as smoothly as possible, no tight bends, and minimize number of bends -- very important. To this I will add that I always use the two-piece clutch rod. Yamaha replaced the one-piece with the two-piece, so they clearly thought it was an improvement.
That's been my experience too. Current bike has original plates, springs, 2pc pushrod and Motion Pro cable. Hot or cold it never drags or slips... neutral is a 1 click affair, and pull is nice and easy. Properly set up, they're as good as any...
 
Some of it is idle speed, which tends to wander on these. Combine a real hot day, a long city ride, and an idle speed that happens to be up there and you can have a small problem with it. Takes a sensitive toe... Wouldn't surprise me if amount of oil is involved too.
 
Cable is new and routed as stock cable would have been, its a nylon lined one and as said all parts new actuator clutch plates, springs, steel plates perfect, new rod which this evening i have replaced with the original two piece all cleaned and polished, adjusted as manual says, will see how it goes on my next ride out, idle is perfect carbs synced and balance no up and down of idle, but as i said in my first post there is a lot of slop in the mushrooms on these and the modification will now be a small project for me.
I will come back on this to let you know how it goes with the two piece rod and the project, i have rode many of these and find them pretty agricultural and that is part of their charm for me, maybe i have been spoilt by smoother running bikes.
 
Being mid summer can you describe the ride conditions in which you were experiencing the symptoms ?
If you were in the burbs on a slow crowded stop and go road I would suspect heat as the biggest contributing cause ?
 
I have an '03 Harley. I was doing an oil change on it one day as I was working on the 75 clutch.
With the H-D primary open I could watch the pressure plate move. I measured it at about 3/8 ".
With the engine cover off the 75 I measured the how much the pressure plate moved. It was about 3/16".
This is barely enough to let the clutch work as well as it could.
All the tips you got are things to get the pressure plate to move as much as it can. Poor adjustment and poorly lubed cable and worm add resistance. are the #1 reason for poor clutch actuation. Anything that causes friction in the cable and worm stretch the cable. Such as poor lube and sharp bends. This prevents the pressure plate from opening fully.
I have searched for clutch levers that can pull more cable. Most are the same with about 5/8 inch.
On the H-D they use a ball and ramp type of actuator. This is two plates with ramps cut in that have ball bearings ride in them. As you pull the lever one plates moves. As the plate moves the ball bearings ride up the ramps to open the clutch.
On the Sportster's had a worm gear kinda like our 650's use Somewhere along the line they changed to the ball and ramp.
I have thought about looking for a Sportster ball and ramp actuator to see if it could be fitted to our bikes.
Just have not gotten there yet.
I think this type of actuator is why the H_D clutch opens more and it works much better. Smoother with a wider sweet spot.
Leo
 
I have an '03 Harley. I was doing an oil change on it one day as I was working on the 75 clutch.
With the H-D primary open I could watch the pressure plate move. I measured it at about 3/8 ".
With the engine cover off the 75 I measured the how much the pressure plate moved. It was about 3/16".
This is barely enough to let the clutch work as well as it could.
All the tips you got are things to get the pressure plate to move as much as it can. Poor adjustment and poorly lubed cable and worm add resistance. are the #1 reason for poor clutch actuation. Anything that causes friction in the cable and worm stretch the cable. Such as poor lube and sharp bends. This prevents the pressure plate from opening fully.
I have searched for clutch levers that can pull more cable. Most are the same with about 5/8 inch.
On the H-D they use a ball and ramp type of actuator. This is two plates with ramps cut in that have ball bearings ride in them. As you pull the lever one plates moves. As the plate moves the ball bearings ride up the ramps to open the clutch.
On the Sportster's had a worm gear kinda like our 650's use Somewhere along the line they changed to the ball and ramp.
I have thought about looking for a Sportster ball and ramp actuator to see if it could be fitted to our bikes.
Just have not gotten there yet.
I think this type of actuator is why the H_D clutch opens more and it works much better. Smoother with a wider sweet spot.
Leo
What kind of spring does that HD clutch have? Diaphragm or coil springs like the XS? Doubling the pressure plate movement will double the force required, on a coil spring clutch. A diaphragm spring has totally different characteristic, as the force peaks, then becomes lower as the spring goes "over center"
 
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As I and others have said, every little thing is important, it all adds up, and all has to be right. You said your cable is new, but you didn't say if it is a Motion-Pro. Forum member TwoManyXS1Bs did a rigorous and scientific comparison of clutch cables and determined that Motion Pro is best. The original OEM cables had an unnecessarily tight metal elbow where the cable enters the sprocket cover. Forum member 5twins made a thread a long time ago about putting that elbow into a vice to take about half of the bend out. That is not necessary with the Motion Pro cable, as it already has relaxed bend.
You also said that your cable is routed as the original would have been. That is not necessarily the best possible routing -- for me it never is, I can always find a path with minimal bends that are smoother and sweeping. Especially if your bars are not stock -- that will completely throw stock routing off.
 
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I have an '03 Harley... Sportster's had a worm gear kinda like our 650's use Somewhere along the line they changed to the ball and ramp.
I have thought about looking for a Sportster ball and ramp actuator to see if it could be fitted to our bikes.
Just have not gotten there yet.
I think this type of actuator is why the H_D clutch opens more and it works much better. Smoother with a wider sweet spot.
Leo
Honda CB350 and no doubt many others use that ball and ramp also I've had the same idear and the same missing round tuit. :laugh:
 
Would the Xs400 clutch actuator modification solve such a dilemma? (This would be a good time for me to do it, with the engine apart, and the clutch cover off...)
 
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