XS650 Clutch Worm Actuator experiment & tidbits

... It appears that the tin seal holder is attached to the arm somehow, spot welded maybe. Not sure those two parts could be separated without damage to the seal holder.

That's right, spot welded! The spot welds are so secure, I decided to leave it together.
 

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5Twins and peanut commented on the binding of the clutch worm when the 2 screws are tightened. During dry-fit testing, I hit the same problem. Never really paid any attention to this before.

Well, found out why the nylon worm binds. The XS left-hand casecover has a manufacturing flaw, or rather a quality oversight. The mount base for the worm has a casting flash that hasn't been properly or fully removed. The 1" hole in the cover has what looks like a slight chamfering in an attempt to remove a raised ring around the hole (pics #1 & #2).

I used an old broken stone that had just barely enough clearance to fit over the mount base, and hand-lapped the surface, removing the raised flash/ring (pics #3 & #4).

Now, when I mount the nylon worm and tighten down the 2 mount screws, the metal worm fits right in, WITH NO BINDING!!!
 

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5Twins and peanut commented on the binding of the clutch worm when the 2 screws are tightened. During dry-fit testing, I hit the same problem. Never really paid any attention to this before.

Well, found out why the nylon worm binds. The XS left-hand casecover has a manufacturing flaw, or rather a quality oversight. The mount base for the worm has a casting flash that hasn't been properly or fully removed. The 1" hole in the cover has what looks like a slight chamfering in an attempt to remove a raised ring around the hole (pics #1 & #2).

I used an old broken stone that had just barely enough clearance to fit over the mount base, and hand-lapped the surface, removing the raised flash/ring (pics #3 & #4).

Now, when I mount the nylon worm and tighten down the 2 mount screws, the metal worm fits right in, WITH NO BINDING!!!

thats excellent work TwoMany :thumbsup: problems invariably seem to come down to poor tolerances or quality control in manufacturing.

I'll remove my cover tomorrow and make the same easement . Excellent I really get some satisfaction on diagnosing problems and solving them even when someone else did all the work lol :D:laugh:
 
that discovery could well be a first TwoMany . :thumbsup:
I hope you get time to write this thread up as a Faq for the tech section .

Its about time someone put together a decent maintenance and trouble shooting guide and published it for the XS650 hint hint :wink2:
 
Pic #1 - The modified worm arm ready for welding.

Pics #2,3 - After welding and grinding. The arm bottom is at the same level as the grease seal bottom, which moves the clevis hole inboard a total of 0.5".
 

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Pic #1 - The next step is to clamp the arm in the vise.

Pics #2,3 - Then the arm is twisted about 6°-7°, so that the cable clevis points directly at the cable entry point in the cover.
 

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Pic #1 - The worm parts are splined, so they're lined-up as they were originally, and pressed back together.

Pic #2 - Then the worm nylon base is fitted to the freshly resurfaced case cover, and the arm/worm assembly is fitted to the nylon worm base.

Now comes the tricky part, the optimum position of the worm arm. We want the worm seated as deeply as possible in the full cable relaxed position, so that full worm travel makes use of all available engagement surfaces, and minimize the 'tipping' torque. We also want the max leverage advantage to occur near the end of cable travel. So we'll find this max leverage point, and work backwards from there.

The edge of the hole in the casecover where the cable emerges into the cavity is a good reference point, so all measurements here will be taken from that point, to the center of the worm arm clevis hole. Pic #2 shows that this fully seated worm arm clevis hole position is 4.5".

Pic #3 - The max leverage point is where the cable termination is at a right angle to the worm center. This point is at 3.7", with an arm length (worm center to clevis hole center) of 1.7". On earlier worms, the arm length is shorter, about 1.3", and the max leverage point is further out, at 3.8".

For this project, we'll use 3.7" as the target max leverage point. Would also like this point to occur at around 80% of handlebar clutch lever travel. The max cable travel is almost 0.65". Accounting for lever slack, stretch, and lost movement, we'll use 0.6" as the max cable travel value. 80% of that 0.6" is about 0.5", and that is where we want the max leverage point.

So, moving backwards by adding 0.5" to the 3.7" position gives us a location of 4.2", which is the ideal starting position. We'll add 0.1" to this to ensure that the worm is off the seating position, which gives us the dry-assembly fully seated position of 4.3". Pic #2's starting position is 4.5", and will need to be adjusted. There's 43 splines on the worm shaft, and with a 4-start worm thread there's plenty of ways to get the ideal position.

Pic #4 - Here's the wrinkle in this plan. The XS clutch cable is TOO SHORT to reach this ideal starting point. With the cable adjuster all the way in, all slack removed, the max reach for the cable puts the clevis hole at 4.1". (I have 3 clutch cables: factory, Mikesxs, and another source. They all have this shortcoming).

This is not a total catastrophe. It puts the max leverage point at about 67% of travel. Might try making a slightly longer clevis, but will save that for another day.
 

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Here's another unexpected wrinkle. The two factory nylon worm bases here are different. The worm base on the left has a raised ridge on the top of the steel shell, prutruding above the nylon. This raised ridge prevents full seating of the steel worm unit, and results in 0.2" of useless cable travel. Simply grinding down this excess 'flange' will solve this. Another something to look out for.

I know that all this sounds like excess fussing, but we're working with a system that's trying to shove a clutch pushrod about 0.060" (1.5mm) against hundreds of pounds of clutch spring pressure. So, every milli-inch counts.
 

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Pic #4 - Here's the wrinkle in this plan. The XS clutch cable is TOO SHORT to reach this ideal starting point. With the cable adjuster all the way in, all slack removed, the max reach for the cable puts the clevis hole at 4.1". (I have 3 clutch cables: factory, Mikesxs, and another source. They all have this shortcoming).

This is not a total catastrophe. It puts the max leverage point at about 67% of travel. Might try making a slightly longer clevis, but will save that for another day.

longer clevis is one way but what about reducing the length of the adjustment screw shank and grinding a new ball interface . You could get about 4-5mm from the non-threaded tip of the screw I reckon :thumbsup:

Excellent work TwoMany that is a significant reduction in clutch lever pull force over stock .
The reduced lever force and increased lever throw could offer a way to reduce lever travel for those with small hands perhaps ?
 

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Hey, peanut, glad you mentioned 'grinding new ball interface'. For this experiment, I've reground and polished the ends of the clutch pushrod and adjuster, flat/square/true. I do NOT want any dimples for the balls, as I believe that the 'dimples' and the side deflection of the original worm setup is the reason for:

- Deflection of the clutch pushrod
- Resulting in additional force to push the misaligned pushrod
- Resulting in some strangely bent pushrods
- Resulting in worn pushrod guide bushing (behind the seal)
- Resulting in worn/leaky pushrod seal
- Resulting in reduced clutch separation travel

The 'dimples' force the balls and pushrod to follow whatever side deflection the worm mechanism exhibits, which can be considerable. I'd rather have the balls and pushrod float, and seek their own center.

I'm also trying to maximize the interface/fit of the nylon worm base and the steel worm drive, to reduce the thread loading per unit area and increase lateral stability/alignment. Take a typical worm assembly, (clean/dry/ungreased), rotate it to its typical 'fully disengaged position' (about 30°-35° from the fully seated position), then apply about 60-100 lbs side force at the same level as the lever arm (which is about what the clutch cable applies). I get about +/- 0.050" (>1mm), due to manufacturing clearances and nylon flex.

I plan to also try this on a new MikesXS worm assembly, to see the benefits, if any, from the new worm material.

I'm ready to tack-weld this puppy, but my welder's down. 22 year old argon regulator blew out its diaphram, new flowmeter will be here in a couple days...
 
I'm ready to tack-weld this puppy, but my welder's down. 22 year old argon regulator blew out its diaphram,

tsk tsk ...typical !:rolleyes:

Things don't last 5 minutes these days lol:laugh:

Funny you should mention the dimple interface . I was thinking earlier today that a dimple interface with a ball bearing sounds on the face of it the ideal solution for this application but like you I am not so sure. If it had any appreciable rotation I'd say the concave surface would increase friction but surely if the dimples are precise they shoud centre the shaft in the tube and reduce friction between the shaft and tube ?
 
Not to change the direction of this thread but I wonder if this will improve finding neutral while at a stop idlng. (I can find it- just gotta blip the throttle up to 2600rpm and then real quick a second pop it into neutral as the RPMS are descending)

Nice investigative problem solving!!!!
 
... if the dimples are precise they shoud centre the shaft in the tube and reduce friction between the shaft and tube ?

You've hit on the issue, peanut. With dimples, the balls and shaft will center on the dimple locations. If the dimple location in the worm moves due to worm deflection, the balls/shaft will follow, and then run out-of-center of the transmission bushing.

I had thought about designing a support bearing to stabilize the exposed end of the steel worm, which would reduce deflection-induced friction and keep the pushrod centered, but figured that was out of the range of a viable field fix.

So, I plan to finish this second version and report the findings. I'm hoping that this mod gives sufficient improvement to warrant field implementations, and perhaps a change to the configuration of the marketed version.

The other challenge is to come up with a way to safely do the mod by others in the field, without complicated jigs, tools and skills. I've straightened-up, fixed, and re-bent the first expermental worm arm, using sockets, scrap steel, vise, pliers and a hammer (no torch this time). Will post a pic and see if anyone can come up with a method.
 
Not to change the direction of this thread but I wonder if this will improve finding neutral while at a stop idlng. (I can find it- just gotta blip the throttle up to 2600rpm and then real quick a second pop it into neutral as the RPMS are descending)

Nice investigative problem solving!!!!

Thanx, Mharrington! And that is EXACTLY the direction of this thread! The clutch/neutral issue has been ongoing for 40 years, and hopefully we can lick this thing. Other bikes of similar design don't have this problem, so there is hope that the XS's problem can be solved.

I believe that the solution is NOT found in a singular fix, but in a combination. The first area to address is the worm-actuator, followed by the clutch (inner oiling and side load management), then the shiftdrum design (possible binding on the fork guidebar?).

Yamaha has implemented various tweaks over the years, attempting to resolve the 'neutral/clutch' issue. I've seen Honda implemented tweaks as well, which were different but successful.

But, that's for a future thread...
 
Here's the cleaned-up re-bent first version worm arm. The distance from the worm center to clevis hole worked out to 1.7".

This was originally a later model worm unit with a factory arm length of 1.8".

The ideal arm length is still experimental, not sure if 1.7" is optimal...
 

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nicely done ! must have been a tricky bend with such a fragile case attached.
Hurry up and get that welder fixed :D

I'm finding this exploration and testing quite exciting ,.... how sad am I :laugh:

My next move would probably be to short circuit the process and look for a more modern design that could be easily adapted to fit an xs650 . I haven't the patience I once had
 
Here's the cleaned-up re-bent first version worm arm. The distance from the worm center to clevis hole worked out to 1.7".

This was originally a later model worm unit with a factory arm length of 1.8".

The ideal arm length is still experimental, not sure if 1.7" is optimal...

On my stock 78SE clutch worm arm, the hole was at 1.78" . I drilled a new hole at
1.44". This improved the push rod motion from 0.079" to 0.097".

I also dimped the worm gear adjusting screw and the long pushrod.

As the engine heats up, the free play at the hand lever increases, so I re-adjust the free play while I'm riding to keep the free play at about 1/16". The result is I can find neutral at any time.
 

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Okay, back to the second worm, awaiting welding:

Pic #1 - Pressed the steel worm apart. Re-indexed the splines to get the proper position.

Pic #2 - The re-indexed worm now seats at 4.3", and is definitely moving upward at the 4.2" position.

This will work fine with the 4.1" cable limitation, and can be used if/when the cable or clevis is extended.

This one will be set aside for a while, awaiting welder regulator, and if I want to change the hole position...
 

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