XS650 Clutch Worm Mod (rebent arm) testing

[TwoManyXS1Bs]

Thanx, Glennpm, it gets interesting...

The second bike to be tested, the 'Bug Killer', has pullback handlebars. The clutch cable is also routed outside the carbs, up under the left side of the tank, then emerging to a gentle swooping curve to the clutch perch. There are no constrictions or tight bends anywhere on this cable. DogBunny claims that he's very meticulous about this clutch, and it shows, the pull is very light.

Pics #1 & 2 - Mid-range pull tests averaged about 10 lbs.

Not shown: Actuator plunge travel was 0.059".

 

[TwoManyXS1Bs]

Pic#1 - The sidecover is pulled and the clevis hole location is measured with the cable still attached. Here, the 3.95" measurement shows that the cable is a little short of the ideal 4.2". The clutch lever will be in the 'best leverage' zone for the first half of clutch pull, then will be falling into the less-advantageous zone in the second half. An extra 1/4" of cable length could help here. We'll see how the mod handles this one.

Pic #2 - The clevis pin 'Start' distance is measured. This 'start' point is where the worm begins to displace laterally from the arm's fully retracted forward position. This measurement is 4.3", so a longer cable will function well here.

Pic #3 - Then the worm arm distance (worm center to clevis pin) is measured, here it shows 1.5".

 

[TwoManyXS1Bs]

DogBunny has the worm arm rebend procedure perfected. He flew thru the mod so fast, I could only get one pic off...

 

[TwoManyXS1Bs]

Pic #1 - The new clevis pin 'start' location is now 4.4", plenty for a longer inner cable length.

Pic #2 - The new arm/clevispin length is a little shorter at 1.45"

The installed cable clevis pin location will be the same at 3.95", a tad short.

 

[TwoManyXS1Bs]

Refit the sidecover and took measurements:

Pic #1 - Actuator plunge travel is now 0.057", a loss of 0.002"

Pics #2 & 3 - Mid-range pull tests ranged from 9 to 10 lbs, no significant improvement here, either.

So the improvement here is also zero, zilch, zip, nada. A slightly longer inner cable might yield a small improvement on this particular bike.

Seeing that this 9-10 lbs of lightweight clutch lever pull on DogBunny's bike is achievable, this is the new target for future clutch mods, as this is probably as good as it can possibly get.

 

[TwoManyXS1Bs]

Clutch worm mod tests, summary.

Quantify these tests, score them, and include them with the previous scores.

Config #10 - 'Yella Tracker', short cable, stock XS worm, 1.35" clevis hole distance
Config #11 - 'Yella Tracker', short cable, modified worm, 1.3" clevis hole distance
Config #12 - 'Bug Killer', stock XS worm, 1.5" clevis hole distance
Config #13 - 'Bug Killer', modified worm, 1.45" clevis hole distance

Closely examining the 'pull' pics, matching pull distances, averaging readings:

#10: Pull-test = 17.8 lbs, Actuator travel = 0.064", Cable tension = 97 lbs
#11: Pull-test = 17.5 lbs, Actuator travel = 0.061", Cable tension = 95 lbs
#12: Pull-test = 10.0 lbs, Actuator travel = 0.059", Cable tension = 60 lbs
#13: Pull-test = 9.5 lbs, Actuator travel = 0.057", Cable tension = 57 lbs

The scoring scheme is: Mills (0.001") per pound of lever pull, scoring factor:

#10: Travel = 0.064", Pull = 17.8 lbs, Mills/lb = 3.6
#11: Travel = 0.061", Pull = 17.5 lbs, Mills/lb = 3.5
#12: Travel = 0.059", Pull = 10.0 lbs, Mills/lb = 5.9
#13: Travel = 0.057", Pull = 9.5 lbs, Mills/lb = 6.0

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

# Score Travel Pull Description
#13: 6.0 0.057" 9.5 - 'Bug Killer', modified worm, 1.45" clevis hole distance
#12: 5.9 0.059" 10.0 - 'Bug Killer', stock XS worm, 1.5" clevis hole distance
#10: 3.6 0.064" 17.8 - 'Yella Tracker', short cable, stock XS worm, 1.35" clevis hole distance
#11: 3.5 0.061" 17.5 - 'Yella Tracker', short cable, modified worm, 1.3" clevis hole distance

And, for comparison reference, the previous scoring table:

#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

Well, it appears that this worm arm rebend mod provides no significant improvements whatsoever on DogBunny's bikes. Disappointing, but this is the purpose of these tests. On the surface, this mod appears to have merit, but maybe only so for particular configurations. Perhaps this mod is only effective when used as part of an overall clutch actuation tune-up. The high scoring value of DogBunny's 'BugKiller' clutch setup is promising, the new 'achievable' target. As for the arm rebend mod itself, for now we'll let the XS community decide.

 

[DogBunny]

Picture to help clarify the modding tool and how it is assembled. Note the flat (red arrow) on the outer piece. When you hammer the arm over, this flat is a "stop," and you end up with a perfect first final bend.
TwoMany left me with 3 modding tool sets. If anyone wants to try the mod, I will ship a set to you for the cost of postage which is $2.75, and then you can ship it to the next person who wants to try it.
I have one cable entry seat re-surfacing tool. It weighs less, so if anyone wants to try that mod, the cost of postage is $2.07, and then you can ship it to the next person who wants to try it.
We did not do a before and after test of the re-surfacing tool, so I don't know how much of an improvement it makes. However, I can attest that it is an excellent tool, and it only takes a minute or two to do what it is supposed to do.
The worm gear mod results were disappointing. The tool works great, but we saw no gains. However, nothing was lost. Both bikes operate just like before.

 

[DogBunny]

TwoMany mentioned that I have an easy clutch pull. Note my cable routing. It makes a single, swooping S-bend. It hangs completely outside the left side of the bike. It passes through or under nothing, and has no attachment points. It is completely self-supporting. It is achievable because of my buckhorn bars -- the cable exits the lever pointing forward, not sideways. It's been like this ever since I got this bike running. I'm not saying that everyone should copy this, the point is that less bends and less sharp bends should be the goal.

 

[glennpm]

Dibs on the seat re-surfacing tool please! Sending my contact info in an email to you.

 

[TwoManyXS1Bs]

DogBunny, thanks again for hosting this evaluation, and the follow-up posts!

Picked-up a really bad flu-type bug in Austin, so my presence will be intermittant...

 

[timbeck]

TwoMany---I thought you were in Austin working on the "BUG KILLER"---tim

 

[80brat]

Hope you get well soon, keep up the good work,THANKS

 

[TwoManyXS1Bs]

Been in bed, megadosing on Vit-C and B-12, Echinacea tea, and my favorite: Nyquil!

Getting better now. Just received (2) 9/16" faucet seat cutters, will give them a try, then make two more sidecover cutters and send them to DogBunny.

Been thinkin' more on this worm mod conundrum, thinkin' that clutch cable friction is a non-linear relative to load, and a mild increase in worm friction results in a multiple increase in cable friction. Tried explaining this phenomena to DogBunny, like where the hero cowboy tries to pull the hapless maiden up the cliff wall with a rope that's dragging on the cliff edge. The harder he pulls, the more the rope tries to dig into the rocks, compounding his load. Well, that's for another thread, experimentin' with clutch cables...

 

[glennpm]

Maybe start thinking about how cables are made for bicycles, i.e., minimize the cable housing to only portions with bends and "un-case" the straights in between?

 

[TwoManyXS1Bs]

Now, THAT puts pictures in my head! Like the old dental drills of the `50s with their articulating arms and exposed pulleys, or aircraft control cables and pulleys. That 20°-30° elbow at the sidecover entry might work better if it was a belcrank?

Could even make that belcrank a kind of harley 'mousetrap' clutch booster, just need to keep it from being 'fugly'...

 

[glennpm]

Yes, bell crank of small pulley with a nylon bushing to rotate on!

 

[DogBunny]

I have two new casecutter sets from TwoMany available to any one who wants them. I also have a couple sets of the worm gear arm bending tool sets for anyone who wants to try that mod.

It occurred to me that when we tested the case cutter tool, we failed to use cutting oil. Using it should make the cutting edges last longer. Motor oil will substitute, and any oil, even olive oil would be better than nothing.

Postage for the worm gear re-bending tool is $2.75, and then you can ship it to the next person who wants to try it.
The casecutter cable entry seat re-surfacing tool weighs less, so if anyone wants to try that mod, the cost of postage is $2.07, and then you can ship it to the next person who wants to try it.

 

[vsop-dk]

DogBunny is it verified and working and there are good results? Great reaup, might miss a point or two at the more technical part... But looks great.

I have two new casecutter sets from TwoMany available to any one who wants them. I also have a couple sets of the worm gear arm bending tool sets for anyone who wants to try that mod.

It occurred to me that when we tested the case cutter tool, we failed to use cutting oil. Using it should make the cutting edges last longer. Motor oil will substitute, and any oil, even olive oil would be better than nothing.

Postage for the worm gear re-bending tool is $2.75, and then you can ship it to the next person who wants to try it.
The casecutter cable entry seat re-surfacing tool weighs less, so if anyone wants to try that mod, the cost of postage is $2.07, and then you can ship it to the next person who wants to try it.

 

[DogBunny]

The casecutter tool was tested by me, and is a great tool, but the mod itself did not apply in my case because I run my clutch cable to the left of my carbs. This mod is for people who run the cable between their carbs.

TwoManyXS1Bs tested clutch pulls before and after doing the worm gear bending mod (which is a different mod) using a digital spring gauge, and determined that it does not make a significant difference.

 

[angus67]

I bet you can have motion pro, or get a DIY cable, and pick up the extra 1/4 inch for the inner cable.
THIS is what modding, and biking is about. its not about how much chrome, or doo-dads you have hanging off your bike, its about how you want to enjoy/ride your bike. Hardtailers included. When I put my chop back together, it only made sense to me the clutch cable should run outside the carbs, and under tank, straight from perch. Ive only one 650, and had no idea the stock cable was routed between the carbs. silly.
Its too bad you two had no improvements.
But, for what its worth, now you know.