XS650 Clutch Worm Actuator experiment & tidbits

Modifying the MikesXS clutch worm arm:

This arm has a different bend profile compared to a stock arm. There is an aggressive blister/bend that starts inside of the seal cup outline, making it doubtful if a decent rebend could be done with the arm attached to the worm. So, the rebend will be done with them apart. First step is to flatten the arm, by beating it into submission with a hammer or:

Pic #1 - Squash the thing in a press. 5 tons used here.

Pic #2 - Nice and flat.

Pic #3 - Mark outline of the seal cup to indicate the edge of the first bend.

Pic #4 - Two bends performed in a vise with softjaws, flatnose punch helps here. The 8° 'twist' bend was included in the bending of the second bend, so a third 'twisting' operation was not necessary.

Pic #5 - Rebend task done, ready for re-indexing (if necessary) and welding.
 

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Worm reassembly, re-indexing, and welding

The factory XS worm has 43 splines, offering multiple re-indexing angles. The MikesXS worm has 38 splines, offering fewer re-indexing combinations.
The hole for the return spring is now 1/2" lower than before, not an ideal location as the new return spring angle is fighting the worm pitch. A new return spring hole will need to be welded at a much higher position.

Pic #1 - The MikesXS worm arm, worm, and seal cup are reassembled in their original places and fitted to the sidecover. Measurement of the fully-retracted inner clevis pin hole location is 4.6", outer clevis hole is 4.8". This may be too far out, the worm will be protruding more than necessary from the worm base before it starts to move the clutch pushrod. With the max leverage point at 3.7"-3.8", the ideal start point would be around 4.3"-4.4", so re-indexing will be explored.

Pic #2 - The re-indexed and welded MikesXS worm. Retracted outer clevis hole is almost 4.5", good enough.
 

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Clutch lever pull and actuator plunge distances of the modified MikesXS clutch worm:

Configuration #7 - MikesXS worm, 1.20" clevis hole distance, modified cable/elbow entry angle
Configuration #8 - MikesXS worm, 1.60" clevis hole distance, modified cable/elbow entry angle

#7: Pull-test = 16 lbs, Actuator travel = 0.062", Cable tension = 96 lbs
#8: Pull-test = 13 lbs, Actuator travel = 0.040", Cable tension = 78 lbs

The clutch lever forces look about right, but the actuator travel values came up quite a bit.
 
Lastly, what I call the 'ultimate' worm, is the fabricated/welded arm version.

Pic #1 - This worm has the return spring perch mounted high, so that the spring pulls more in-line with the worm's spiral path.

Pic #2 - The clevis hole is 1.65" from the worm center, and the arm was re-indexed to get the clevis hole at 4.35".
 

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Clutch lever pull and actuator plunge distances of the 'ultimate' clutch worm:

Configuration #9 - Ultimate worm, 1.65" clevis hole distance, modified cable/elbow entry angle

#9: Pull-test = 14 lbs, Actuator travel = 0.058", Cable tension = 84 lbs

This one works very well, will ride around on this one for awhile.
 
Rode around a bit with the actuator dial guage mounted, observed plunger travel during various clutch events.

At a plunger value of zero, the clutch is fully engaged, of course.

At plunger values between 0.012" (0.3mm) and 0.016" (0.4mm), the clutch is in the 'feathering' engagement zone.

While releasing the clutch lever, you can feel the clutch begin its engagement at 0.016" (0.4mm), then reach full grip at 0.012" (0.3mm).

At plunger values between 0.016" (0.4mm) and 0.030" (0.75mm), neutral is difficult to find when stopped in first gear.

At plunger values above 0.030" (0.75mm), neutral is easy to get when stopped in first gear.

This is on a warmed-up high-mileage XS1B, with a low-time clutch (7-disc upgrade).


Edit: 2-23-2017, just to clarify this post.

This means that there's 4 zones in this clutch's personality.

1- Initial take-up, 0.000" - 0.012"
Pushrod parts get compressed, the left cover flexes outward, the mainshaft double-row bearing shifts to the right, and pressure on the clutch reduces, but the clutch is still engaged.

2- Feathering zone, 0.012" - 0.016"
The clutch is slipping, but still transmitting torque.

3- Drag zone, 0.016" - 0.030"
That mysterious area where neutral can be difficult to find.

4- Clear zone, 0.030" - and beyond
The clutch viscous drag is minimum, neutral is easier to find.
 
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Summary and Analysis, hold on....

Config #1 - Stock XS1 worm, 1.3" clevis hole distance
Config #2 - Arm bent down 0.4", 1.3" clevis hole distance
Config #3 - Arm bent down 0.5", 1.7" clevis hole distance
Config #4 - Arm bent down 0.5", 1.7" clevis hole distance, modified cable/elbow entry angle
Config #5 - MikesXS original worm, 1.35" clevis hole distance
Config #6 - MikesXS original worm, 1.75" clevis hole distance
Config #7 - MikesXS modified worm, 1.20" clevis hole distance, modified cable/elbow entry angle
Config #8 - MikesXS modified worm, 1.60" clevis hole distance, modified cable/elbow entry angle
Config #9 - Ultimate XS worm, 1.65" clevis hole distance, modified cable/elbow entry angle

#1: Pull-test = 25 lbs, Actuator travel = 0.062", Cable tension = 150 lbs
#2: Pull-test = 18 lbs, Actuator travel = 0.064", Cable tension = 108 lbs
#3: Pull-test = 14 lbs, Actuator travel = 0.046", Cable tension = 84 lbs
#4: Pull-test = 13 lbs, Actuator travel = 0.051", Cable tension = 78 lbs
#5: Pull-test = 15 lbs, Actuator travel = 0.045", Cable tension = 90 lbs
#6: Pull-test = 12 lbs, Actuator travel = 0.034", Cable tension = 72 lbs
#7: Pull-test = 16 lbs, Actuator travel = 0.062", Cable tension = 96 lbs
#8: Pull-test = 13 lbs, Actuator travel = 0.040", Cable tension = 78 lbs
#9: Pull-test = 14 lbs, Actuator travel = 0.058", Cable tension = 84 lbs

Well, this is a bunch of mumbo-jumbo, how to make sense of it all?

We can calculate a scoring value for each, and sort on those values. Since we want more actuator travel, but less lever effort, let's try a simple ratio, like plunger travel in mills (0.001", millinch, thousandts-of-an-inch) per pound of lever effort. In the ideal/frictionless environment, the XS clutch mechanism would get close to 10 mills (0.010") for each pound of pull, so 10 is the perfection value, everything else comes below that. This is, in a way, a measure of machine efficiency, on a scale from 1 to 10, and is what we're pursuing.

New list, showing mills/lb scoring factor:

#1: Travel = 0.062", Pull = 25 lbs, Mills/lb = 2.5
#2: Travel = 0.064", Pull = 18 lbs, Mills/lb = 3.6
#3: Travel = 0.046", Pull = 14 lbs, Mills/lb = 3.3
#4: Travel = 0.051", Pull = 13 lbs, Mills/lb = 3.9
#5: Travel = 0.045", Pull = 15 lbs, Mills/lb = 3.0
#6: Travel = 0.034", Pull = 12 lbs, Mills/lb = 2.8
#7: Travel = 0.062", Pull = 16 lbs, Mills/lb = 3.9
#8: Travel = 0.040", Pull = 13 lbs, Mills/lb = 3.1
#9: Travel = 0.058", Pull = 14 lbs, Mills/lb = 4.1

Finally, sort the list by score, highest score first:

# Score Travel Pull Description
#9: 4.1 0.058" 14 - Ultimate XS worm, 1.65" clevis hole distance, mod cable entry angle
#4: 3.9 0.051" 13 - XS worm, arm bent down 0.5", 1.7" clevis hole distance, mod cable entry angle
#7: 3.9 0.062" 16 - MikesXS worm, arm bent down 0.5", 1.20" clevis hole distance, mod cable entry angle
#2: 3.6 0.064" 18 - XS worm, arm bent down 0.4", 1.3" clevis hole distance
#3: 3.3 0.046" 14 - XS worm, arm bent down 0.5", 1.7" clevis hole distance
#8: 3.1 0.040" 13 - MikesXS worm, arm bent down 0.5", 1.60" clevis hole distance, mod cable entry angle
#5: 3.0 0.045" 15 - MikesXS original worm, 1.35" clevis hole distance
#6: 2.8 0.034" 12 - MikesXS original worm, 1.75" clevis hole distance
#1: 2.5 0.062" 25 - Stock XS1 worm, 1.3" clevis hole distance

Having ridden around with all these different configurations, and knowing the zones for clutch engagement and finding neutral, and experiencing the typical XS 'expanding case' slackening issue, I personally wouldn't use any configuration that didn't produce at least 0.050" of travel. Would also prefer the 'lighter' clutch pull, selecting those under 18 lbs. So, weeding those out we get:

Selected clutch worm configurations:

# Score Travel Pull Description
#9: 4.1 0.058" 14 - Ultimate XS worm, 1.65" clevis hole distance, mod cable entry angle
#4: 3.9 0.051" 13 - XS worm, arm bent down 0.5", 1.7" clevis hole distance, mod cable entry angle
#7: 3.9 0.062" 16 - MikesXS worm, arm bent down 0.5", 1.20" clevis hole distance, mod cable entry angle

Just so happens, these are the top 3 scorers. So, I'm currently using #9, the 'ultimate' XS worm. Works fine so far.

=== End of clutch worm experiments, for now ===
 
Nice work Two many. The mikes arm appears not to have been spot welded. The pictures show it all fantastic job. I have been following this thread with interest. A lot of time spent but well worth it. Better than sitting around doing nothing. The weather has turned cold and the worm drive project on hold. I did manage to get a short ride been doing carb evaluation. Might raise the needle or not. Did you try the EZ pull I used the rubber cover of the elbow to cover the end. Looks better and covers the hole in the cover to shed the elements. No wiggling noodle anyway. Long range evaluation at your leisure. Cold Weather and old broken bones don't mix if the weather permits :shrug: I'm done testing. Now the bending process could probably be done on that press think off set die. :cheers: I hate winter. Well done :thumbsup:
 
Thanx, scabber. This mess will be continued in other supporting threads, dedicated to a specific area, like clutch cables(including that EZ-pull), clutch pushrods, then pressure plate and springs. So this whole clutch thing isn't over yet. The ideal clevis hole location will depend on the outcome of those next experiments.

Rubber boot to cover the EZ-pull end, good idea. Wiggling noodle, hahaha, gotta remember that one.

Yeah, a press die! Thinkin' on that. Visions of squashed worms giving their lives to perfect that thing.

Currently trying to make 3 piloted counterbore cutters, for the cable entry hole recut in casecovers. Trying for 9/16" 6-flute cutters with 1/4" x 4" pilot. Couldn't find anything budget-oriented like that on ebay.

Planning on going to Austin in a few days, after this cold-snap, and hook-up with DogBunny. We'll see how well this could be implemented, and if it really does work on other bikes. I've never worked on any other XS's but my own `71s, much less actually seen other XS's, except for his.
 
Boy, I swear, I just don't believe this. I feel like an idiot for not researching this fully.

5Twins got me started looking into the XS500 clutch pushrod, so while researching those, found these pics of the XS500 clutch worm, the first pic from our sister xs400 forum. The arm is bent in the correct direction! It appears that someone on the XS500 design team knew what they were doing. Now, why didn't this design transfer over to the XS650? Sometimes you wonder if the left hand knows what the right hand is doing (don't answer that!).

This is encouraging, however, as it reinforces this 'rebent arm' concept, almost an endorsement of this mod.

Although the XS500 worm is very similar to the XS650 worm, same rotational direction, I'm not sure if they'll interchange. Would need to test-fit one in an XS650 nylon worm body. The arm length is short, like the early XS1-XS1Bs, so it may be functional but not suitable.

The XS850 clutch worm also looks similar, just doesn't have the bend in the arm (couldn't snag a pic).
 

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Wow, DogBunny, that worm's got quite a history! Makes me wonder even more why Yamaha didn't use the XS500 arm geometry on the XS650s.

Here's another coupla questions. Why does the MikesXS worm have the finer pitch? Is this patterned after another different worm design?
 
Why does the MikesXS worm have the finer pitch? Is this patterned after another different worm design?
If you ask me, it's because the Chinese copiers can't get things right. Lots of the MikesXS repops differ from the real thing in significant ways. I have pointed out critical differences in the MikesXS jet nozzle needles before. How hard is it to measure and copy a little piece of metal the size of a jet needle?
 
DogBunny---You need to go easier on the Chinese copiers, they are only 11 years old---
 
I have read this about 10 times cant wait to do mine GOOD STUFF HERE THANKS 2MANY

Holy bleeding eyeballs! Great to hear the enthuiasm 80brat. Would be great to hear if others have done this, and their evaluations.

Would be even greater to get thru this cold snap so we can go back to playin' outdoors!
 
Threw this together from scrap metal. Case cutter tool to recut the clutch cable entry hole. The cutter works like a 9/16" 'reverse counterbore' or 'spot facer'. The long pilot ensures that the cut surface will re-aim the clutch cable to the new clevis location.

Pic #1 - Piloted cutter and guide plate

Pic #2 - Fitted to a sidecover, ready to cut
 

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This thread and your work keep getting better!

Hey, glennpm, thanx! 'Bout lost my mind trying to grind that cutter.

The plan is to pack-up all this stuff and head over to DogBunny's to do a test mod. We'll take before and after measurements, DogBunny will do the mod, I'll hover and take pics. We'll see if it's do-able in the field, find problems, and, more importantly, it it actually nets any benefit on another bike. Doing this on just my bike isn't the best test.
 
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