MOTORCYCLE CLUTCH TUNING

- by Pete Snidal (C)2001

Slip and Drag. The two problems you can run into with any clutch. Brit bikes (and their "equivalents" - Indian Enfields) have their share of these woes, but the Good News is that these things aren't rocket science, once you've been through it a few times.

First off, dragging - grinding into first. If this is a problem, there are a couple of procedures that may help. First off, try pulling in the lever before you start the bike, and kicking it over a few times in neutral. This will break the clutch free (hopefully), and it (again hopefully) will free up again after you start the bike to put it into first gear. Second, "blipping" the throttle with the clutch disengaged, before you punch it into gear will often aid in freeing the clutch as well.

After a long period of sitting, it's common for clutches to be a little sticky for the first few starts. I've found that, after a winter's storage for instance, it's helpful to get the bike rolling before engaging first gear. At idle rpm, you only need to be moving at a fast walk to put the thing into 1st, without any clutch disengagement at all, really. Then when it's in gear, disengage the clutch and come to a stop, and start and stop a number of times, slipping the clutch a little more than usual, to shine things up in there. By the time I've ridden it a bit, the stickiness is usually gone.

But, if all this leaves you sans cigar, it's time to get to work. You may even have to Go In.

Are Some Worse Than Others?

Triumphs, as Brit bikes go, were notoriously bad for grinding into 1st gear. For years, I just accepted this as a fact, as all my Triumph-riding friends seemed to have the disease. Never paid much attention, really, as I was a dyed-in-the wool singles fan at the time, and my Royal Enfields, AJS, Velocette, Gold Star, and Norton International kept me busy enough sorting them out.

And many years later, I think I figured out why the Tris were such bad grinders! It was just because they were about the hardest to get the clutch apart for cleaning! Enfields, on the other hand, were about the easiest. One bolt for the footpeg, and one for the chaincase, and you're in there! No gasket, just an infinitely reusable giant O-ring. Three conventional capscrews for the clutch pressure plate, (and no spring adjustment required on reassembly) and you're cleaning plates already! For many of the others, lots more chaincase bolts, a gasket that often required replacement, all in all, lots more bother, so the clutch didn't get cleaned very often. And, although they're an oil-bath clutch, designed to run in the primary oil, it seems that to clean them off and leave them to re-oil themselves once in a while makes them work a lot better!

Worked all this out when I started riding Tris pretty well exclusively myself about 20 years ago - after a number of years of keeping to dirt bikes, by the time I got interested in street riding again, Triumph twins were about all a guy could find any around any more. So I set to getting on top of the problem, and now my "69 TR6 goes into gear from cold with nary a sound, and with just a bit of a snick when hot. Here's what I've found, over an number of years (and Triumphs.) These truths apply to just about any motorcycle, especially a Brit one:

Step 1: Adjustment

First, adjustment is important - you need to have maximum throwout stroke applied to the pressure plate, yet have enough free play in the linkage so that there will be no drag on the throwout mechanism. The TM is, in order, the handlebar lever, the cable, the rotary ball-and-cam gizzer in the gearbox cover, which converts the straight pull from the cable end into push down the hollow gearbox mainshaft to the clutch pressure (outside, spring-loaded) plate inside the primary cover.

OK? The idea is to adjust at each of the possible spots for max throw with just a teensy bit of play. If you have less than 1/8" of cable movement at the handlebar lever before you feel things engaging, it's probably fine the way it is. If you have more slack than that, you'll have to tighten things up a bit. Start by checking the pushrod (through the gearbox) free play. Loosen the clutch cable at the handlebar end with the adjusting nut, to ensure that the ball-and-cam gizzer has no pressure on its cable end. Now, you're ready to check the end play of the pressure plate rod that goes from the gizzer inside the gearbox cover through the mainshaft to the clutch pressure plate.

The adjustment screw will be at one or the other end - in the gizzer itself, or in the clutch pressure plate. For Triumph twins, you can unscrew the big slotted plug in the rear of the primary chain/clutch case cover, and you'll find an adjustment screw, with a locknut around it, in the clutch pressure plate.. Enfields provide this adjustment at the gizzer end, under a cover plate in the center of the transmission cover. In either event, you'll want to loosen the locknut and turn the screw clockwise unitl you feel resistance/tightness. Back it off a smidge, and it's time to tighten the locknut back down. Before you do, note the position of the screw slot, so you can be sure it hasn't moved as you tightened the locknut with a socket wrench/spanner. You have to tighten the locknut without moving the screw, or more realistically, in such a way that when your'e finished, the screw is in the position mentioned above. (Through a little hole in the chaincase? Go ahead - I dare ya! This may require a few cut-and-fits; it's much easier with the chaincase off, so you can use a box-end wrench/spanner on the nut while holding the screw with a screwdriver, but it can be done with care through the hole - sort of like buttonhole appendectomies.) Starting by semi-tightening the locknut, then backing off the screw a bit more, so that when it inevitably tightens again as the nut is tightened is generally part of the technique. It it gets entirely too frustrating, it may be time to think Y*ha.

Once your pushrod is adjusted, tighten the clutch cable with the handlebar lever nut/locknut arrangement. Same procedure - tighten from slack until you feel resistance, then back it off a tad. You want about 1/16" of free play. Does the lever feel spongy? If so, your outer cable may be stretched and springy, or your inner may be too thin. You may want to replace it, but this is not likely.

Now, you should have proper thorowout movement. It may not be enough; In the case of the Triumph, if the four pressure plate springs are not adjusted evenly, the plate will not run true and this will cause drag, but that's to check later, if the "case-cover-on" procedure isn't enough. (The Enfield clutch springs are non-adjustable; just tighten the three capscrews fully, and you're there. Or not.

Dirty Plates?

If adjustment didn't fix your problem, it may be dirty plates. Both drag and slipping can often be corrected simply by cleaning the plates, both friction and steel. (Well, they're ALL friction, but some are coated with a friction lining, and some are just plain steel.)

Although they run in oil, it seems that if they get TOO oily, they drag or slip. Strange but true. I discovered that cleaning solved a lot of problems in my early days with Royal Enfield singles, as mentioned above. It was a simple and regular procedure to tear the clutch apart and "wash the dishes" - wash all the plates in gasoline (what, me leaded?), throw it together, dump in some more 20wt, and ride on. But my Triumph riding friends found this to be a lot more trouble, so they'd just make fun of my "high-maintenance" Enfields, and ride on grinding all the way. Your mileage may vary. but I suggest that the second stage of dealing with a grabby or slipping clutch should be cleaning the plates.

The Easy Way

Like the man says, there's an easy way, and a hard way. The easy way is the "clutch flush." This can only be done, however, in bikes which DO NOT share engine oil with the chaincase. This would be all Enfields, Royal and Otherwise, and the earlier Brit bikes in general. Triumph changed their crankcase breathing system, incorporating the chaincase with the rest of the engine, just before the OIF frames - mostly about late '69. You have to be careful with these. Tip-offs are:

If you have this system, the only way to clean your clutch will be to dismantle, clean, and reassemble. This will also take you to stage III - the checking of the pressure plate for runout. If your oils are not shared, then you can do

The Fast Flush.

For the FF, all you do is drain the chaincase, refill (don't even measure, just pour in a beer bottle full (384 ml, 12 Oz.) of washing solvent, and replace the filler plug. Start the bike, and go for a short ride. Use the clutch a lot, slipping, disengaging while in gear, blipping the throttle, doing all you can to slosh that solvent around between the plates. After a few minutes of this, back to the shop or driveway, drain the solvent into your parts washing system (a $300 parts washer or an old hubcap), refill according to specs with type F Automatic Transmission Fluid, and carry on.

Automatic Transmission Fluid?

ATF is formulated to lubricate the needle bearings, bushings, chains and such in Automatic Transmissions, and is just the thing for their clutches as well, which look just like ours. Type F was developed for Ford, who wanted a little more friction in the clutches, just like (often) us, is easily available everywhere, and looks nice. It also starts out bright red, and will go black if your clutch slips excessively. The Right Stuff.

Stage 3

Stage III involves dismantling the clutch. This is the court of last resort for those who have done the flush and still not attained bliss, or those who didn't have the Flush option. Drain the chaincase (this may involve draining the whole motor), saving the oil if it's still fairly clean, and it's not time for an oil change. Remove the cover, after having unfastened whatever appurtenances are necessary, and dismantle the clutch. Be sure to make a note of how tight the spring nuts are - this will be your baseline for reassembly adjustment.

As you remove each plate, wash it off in washing solvent with a stiff brush, and set it out to dry. Check the drive tangs and tabs of each plate, and the slots in the hub or clutch basket to see that excessive burring hasn't occured - this can limit the mobility of the clutch plates on disengagement and cause drag. The cure for this is usually replacing the basket and/or hub, and/or some or all of the plates, although careful work with a file can sometimes obviate the necessity.

You will also want to check the condition of the friction material on the friction plates - it's nice to see a new one once in a while, so you know what to look for, but basically you want the material all to be there; if it's starting to peel off, you know it's getting too thin. You want to replace the friction plates before this happens.

You'll also want to inspect the springs. They want all to be the same length, and not discoloured due to overheating. Once again, it's nice to have new ones for comparison, but I always count on them not all being weak at the same time, so if they're all of a length, I usually assume that's good enough.

Remantling

Reassembly of the clutch will require, in most cases, adjustment of the pressure plate springs. You want even tension on each one. Check by disengaging with the lever, and pushing the kicker. The pressure plate wants to rotate with no "run-out." Get it this way, and with enough tension, and it should disengage. Not enough tension will result in a clutch that disengages nicely, but slips in operation. That's why you noted the position of the nuts on their screws when you dismantled. If it was slipping, you may want to tighten a bit.

Once you've got it all back together, you'll want to check your push rod play again - step one above - since it may have changed as a result of your ministrations. Then on with the cover, using a new gasket and/or doping with your favourite preparation (mine are CopperCoat or Silicone). Fill to spec with ATF type F and carry on. It should work now, I hope it does.

So, see? Jus' like I said: simple, huh? A few hours of fiddling with the things, and you too will be a clutch expert.