Clutch Lever Reach Reduction Farkle ( ST1100 ) *

[KoTAOW]

CLUTCH LEVER REACH REDUCTION FARKLE

by Steve Chamberlin, STOC1835 April 2002

INTRODUCTION:

I had been following with interest threads that had popped up on the STOC email liST over time which identified various adjustable clutch levers from other Honda model bikes that would fit the ST1100 and had the potential of reducing the reach required to operate my 93 STs clutch lever. My hands are not large, and one of the few weaknesses I had identified from the first test ride was the awkwardness of operating the clutch compared to other bikes I have ridden, due to the fact that I was grabbing it pretty much close to my fingertips. Not a showstopper, but one of those things that if it could be improved, it would be good. None of the replacement levers appeared to be a perfect appearance match, or they were a little pricey, or offered unknown actual improvement. I really didnt care about the adjustability, as I expected I would find the closest position and just leave it there. So I decided to see if the stock lever could be permanently modified to reduce the reach. I found that it indeed could on mine, and the improvement in ease of clutch operation and smoother clutch engagement are amazing. So I hope that these instructions and very non-professional photos might help anyone else who wants to try this. It is not difficult (although these instructions are long, only due to my anal sense of detail, dont let that put you off).


PARTS REQUIRED:

None. However, I did find that the rubber boot that goes between the actuation rod and the clutch master cylinder housing was torn on mine, so I got it ahead of time and replaced it. Taking the boot out during the work improves your feel for the measurements you'll make, and it may be damaged on removal, so for a $7 item, it seems wise to just get a new one before you start. The part # for my '93 was 45504-300-003, I assume it's the same for all, but check it.


TOOLS:

The only unusual tool I think is so helpful that you really should have it for this job is a 6" vernier caliper for taking measurements. The one I have is plastic, no dial, and I think they are available at many places for less than $10.


INSTRUCTIONS:

The one characteristic of my clutch that made this possible was that there was a good deal of wasted motion in the lever travel. That is, when starting from the lever pulled fully against the grip, I had to let the lever out quite a ways before it would do anything, then there seemed to be a fairly short engagement zone close to fully released, where I had poor leverage. The photos at right of the clutch and brake levers looking down from above show that the clutch lever is clearly further from the grip than the brake at their stops. So the objective was to eliminate some of the wasted motion and in the process move the stop position and engagement zone closer to the grip. The measurement of the lever action and determination of the target final lever position is first step. Note that this may not be able to be done to every lever, your measurements of where clutch engagement begins must determine that.






1. As shown in the photo at right, I took all measurements with an inexpensive vernier caliper, and measured between opposite sides of the grip and the ball at the end of the lever, with the caliper held perpendicular to the grip. This provides a consistent and repeatable measurement. Take and record this measurement with the lever tight against the grip, and with it fully released. Mine was 50.5 mm tight and 148.5 mm released, so I had a total travel of 98 mm, or 3.9 in. By contrast, the released position of the brake lever where I have it adjusted as far in as it will go is 122 mm, or slightly over 1 in. closer.





The critical measurement is to determine the position of the point of first engagement when releasing the lever when in gear. Clearly some clearance short of this point is necessary to ensure full clutch disengagement with the lever pulled all the way in. I did this measurement with the bike cold (about 50 F ambient) and also with it fully warmed up to see if there was a difference (there wasn't much).

Adjust the caliper to about a 55 mm opening. With the bike on the center stand, the left pannier removed, the engine running at normal idle speed, and you standing on the left side, fully pull in the clutch with your right hand, put it in gear (first or second), and with the left hand, place and hold the caliper against the lever ball end and spanning the grip. Watching the rear wheel, slowly let the clutch out continuing to hold the caliper in position as the lever moves, which will open up the caliper. When you see rotation of the wheel just beginning, pull the lever back in and return it to neutral. The caliper will now display the distance to the point of first engagement. (Actually it's to the point of transmitting enough torque to barely overcome brake and driveline seal drag, but it's close enough.) Repeat this five to ten times. (In case your bike has very little brake and seal drag and you find your wheel rotating just from the oil's viscous drag, you can imbalance your rear wheel by taping a weight like a hammer head to the O.D. of the tire, then let the lever out just enough to hold the weight at axle height. If you do this, check to ensure the wheel can go all the way around without the weight hitting anything, including the ground, in case you accidentally get the wheel going!)

I did this with the bike cold and hot, in second and first gears, with the following results, all in mm:

Cold, 2nd gear:  Max   102;  Min   96;   Avg   99.2

Hot,  2nd gear:  Max   101;  Min   97;   Avg   99.4

Hot,   1st gear:  Max   101;  Min   95.5; Avg   98.3

Subtracting the 50.5 dimension, then, I had free travel up to the point of engagement of 45 mm minimum, or 47.8 mm average, or about 1.75 mm 1.9 in. I was confident I could take an inch out, and seeing that this would result in it being close to the brake lever position, I went for balance and decided to set it the same as the brake, at 122 mm, making the lever about 1 1/16" closer.


2. Having determined the new fully released position of the lever, hold it in that exact position using tape, as shown in the photos at right. Fiberglas reinforced strapping tape is perfect for this as it does not stretch.



Then using a sharp awl or pencil, scribe a line on the brass insert that is in line with the machined end of the upper pad of the master cylinder housing that partially covers the insert.

Then remove the tape and allow the lever to go to the fully released (clutch engaged) position. Again scribe a similar line on the insert. The distance between these two lines is the amount that you will reduce the length of the pushrod.


3. Remove the lock nut and unscrew the pivot shaft from the master cylinder/lever assembly, but do not remove the lever. Holding the lever snug against the stop and the pushrod but without causing the cylinder to stroke at all, note that the lever pivot bushing is slightly offset to the left of the pivot pin bore by about 1 mm, as can be seen in the photo at right. Take a good look at this, when you are adjusting it to the new stop position, you will need to achieve this same offset. Reinsertion of the pivot pin requires a slight compression of the piston to allow the holes to line up. This ensures that there is spring force on the lever when fully released to eliminate rattle. Too much offset, however, and the bleed hole between the reservoir and the cylinder could be covered up by too much pre-stroke of the cylinder.



Remove the lever (the brass insert may drop out at this point, take care to not lose it). Using the vernier caliper, measure and record the distance between the lines you have scribed on the insert. Clean the round surface of the insert to promote easy rotation in its bore.


4. Remove the pushrod, it is only held at this point by the rubber boot, just pull and it will either come out of the boot, or the boot and pushrod will come out together. If the boot didn't come out, pull it out anyway (it's held in only by friction between the boot and the bore, although corrosion in there could make it sticky), you will want it out later when refitting the modified parts. When separated from the boot, note which end of the rod is out (the end opposite the spherical end), this is the end you will be shortening. The photo at far right shows the rod before shortening assembled with the lever and brass insert. Note that depending on how much shortening you do, there may be interference between the lever and the step for the boot groove. This will be addressed in step 5.





Using the calipers, measure and record the length of the rod. Subtract from this length the distance between the lines on the brass insert which was previously measured. This is the new length of the shortened rod. Note the rounded corners of the rod end you will be shortening.

Using a file, or a hacksaw and file, carefully shorten the rod at the end that goes into the insert until the length equals that calculated earlier in this step. Duplicate the corner chamfer noted earlier to ensure that the rod will bottom in the insert against its end and not on the corners.




5. In my case, I did observe the slight interference mentioned above after shortening the rod and trying it back in the insert. So I filed a small relief as shown in the photo at right the upper filed surface. If you need to do this, take care to file no closer to the pivot point than shown, that surface depresses the clutch microswitch and must remain unmodified. You can probably tell where the microswitch hits by examining for a slight mark on the lever, this can be seen on the enlarged version of this photo. The second photo shows the rod assembled with the lever after shortening and filing the relief.

In preparation for building up the stop with epoxy, file the paint off the stop. Not completely trusting epoxy to simply adhere to the smooth aluminum surface there, I also drilled a small hole as can be seen in the left picture above, taking care to not go through the back side of the stop. When filled with epoxy, this will provide an integral post to help the block of epoxy stay in place. I also recommend chamfering the top of the hole to avoid creating a sharp corner between the post and the block, which could be a stress riser and might promote cracking there.


6. The thickness of the epoxy block added to the stop will be a little less than the amount removed from the rod, but you want to leave extra to file off to get the right surface orientation and position, so plan to add the same thickness you removed from the rod to start with. Cut a small strip of duct tape and wrap it around the stop as shown at right so that the top edge is where you want the top surface of epoxy before filing.





Position the lever so the top edge of tape is horizontal. Mix epoxy (I used Duro Metal Repair, but I'm sure J.B. Weld or any other good epoxy would work fine, it will only be in direct compression) and using a toothpick, carefully fill the hole with epoxy, being sure not to trap any air in the hole. After the hole is filled, fill the remaining portion enclosed by the tape up to the top. Due to the flow-ability of the epoxy, over time the sides of the tape will bulge. If you wish, you can reshape them slightly with finger pressure as it's hardening, but you'll be filing them to final shape anyway so it's no big deal.


7. After allowing the epoxy to thoroughly harden (I waited overnight) remove the tape. The block should look something like that at right. For shaping of the block, a Dremel tool with a small sandpaper disk works well since almost no pressure is required to remove material. But a regular file works fine too. Shape the top and bottom surfaces of the block so they are co-planer with the neighboring cast surfaces, and create a radius at the corner furthest from the pivot so it clears everything when in motion, as shown in the photo to far right. Test fit the lever with the pivot screw dropped in but without the rod in place and it should require filing of the contacting stop surface. Gradually file this surface and keep trying it until you are within about of the final position. Maintain the surface parallel to the mating stop surface, or even slightly rounded such that the actual contact on the epoxy takes place in the center of the surface, not on the edge, which might cause chipping.



From here on, test fittings should be conducted with the rod in place but without the pivot pin, holding the lever snug against the stop and the pushrod but without causing the cylinder to stroke at all. Continue gradually filing the stopping surface and trying it until you get the bushing to that same slight offset between the bushing and the pin bore that will maintain a little cylinder spring force on the lever when let out. When you try it then with the rod in place and the pin inserted, the lever should be close to or right at your targeted position. Fine tune as required. If you go too far with the filing, you can always add a touch more epoxy and go at it again.


8. Now you can assemble the boot to the rod (a little lubricant makes this easier) and then insert this assembly into the cylinder. A little pressure with the end of a screwdriver on the ring of the boot that is down in the bore will help it seat. Put a light coating of lithium grease on the brass insert and on the pivot pin, and attach the lever with insert, the pivot pin and lock nut and check all motion for interference anywhere. Comparing the photo at right (modified) and far right (original) should make it clear what a huge difference this has made. Although this procedure does not change the action of the cylinder itself, the increased leverage made it feel to me as if the engagement zone had been made longer and easier to feather, and the lever easier to pull in, perhaps because now I can grip it closer to its end for improved mechanical advantage, and with fingers curled, which allows bigger hand muscles to be used.




9. GO RIDE!!!


I hope this helps. I've done quite a few farkles to my ST, and this is one of the best.

Steve Chamberlin -  Iowa

93 STA STOC1835 HSTA9548SU

~~~

Thanks to Eric J. Russel for acquiring all the missing photos to complete this article.