Setting up the clutch

With the gearbox now properly located and installed I checked the alignment of the crankshaft sprocket with the clutch sprocket (the slight burrs present on the teeth as desribed in the previous post, were easily removed). A steel rule and taught piece of string showed they were aligned to within 25 thou inch. So far so good.

I could not find a torque setting for the crankshaft sleeve bolt and the only advice on the 'forums' was 'do it up tight'. I tightened it with a socket and a normal length rachet bar, checked with a torque wrench it was 55 ft lb. This time it had a good application of blue loctite.

With the clutch back together (centre nut 50 ft lb plus loctite and locking washer) it is time to replace the plates, set the clutch spring tension and make sure the outer spring plate moves out squarely when the clutch is operated.

Make sure the clutch pushrod is straight (roll it along a piece of glass to check). Also, make sure it is the correct length, there are a number of alternative lengths, my 51 6T uses an 11 3/4 inch rod. Ensure it engages with the adjuster stud that is located behind the hexagon cover on the outer gearbox cover. It is also a good idea to slacken off the clutch cable at the gearbox end so the pushrod arm is not exerting any pressure on the pushrod. Put some oil on the pushrod and a blob of grease in the cupin the centre of the outer spring plate into which the rod fits.

There is no precise 'setting' for how much the clutch spring nuts need to be tightened as it depends on the length of the spring threaded studs and strength of the springs (I bought new studs and one was about 1/8 inch shorter than the others !). A good starting point is to adjust so that the end of the stud is level with the face of the spring nut. If you tighten them too much the clutch will not slip but the clutch lever will be hard to pull in and the clutch may 'drag (not fully release), Not enough and the clutch will slip. I set mine with one thread of the stud showing above the nut (the lower left is the shorter stud so it is just below the face of the nut). I tried it with the stud fractionally below the top of the nut and the clutch slipped so, on my clutch, the adjustment appears to be quite sensative.

At this point you can adjust the clutch cable and arm. The stud which pushes on the pushrod should contact the end of the rod with the arm about 15 degrees before it reaches the vertical, and when the clutch lever is fully pulled in the arm should be vertical. If the arm goes past the vertical the stud can push down on the end of the pushrod and bend it or, as the last half inch or so of the rod is (or should be) hardened, break it off. You can then adjust the cable to give about 1/8 inch free play at the lever end.

Once you have got to this stage you need to adjust each nut so that the spring plate (the black cover plate) moves out squarely when you pull the clutch in. I use a dial guage against the rim of the cover and turn the clutch by putting the bike in gear and turning it with the back wheel (with the rear drive chain in place) and the spark plugs out (putting the plugs back in the caps and placing the threaded part of the plug on top of the sparkplug hole is a good idea as the magneto will put out a voltage when you turn the engine over). I then pull in the clutch lever enough to move the cover plate outwards by a small amount. I put a 1/4 inch bolt between the clutch lever and lever bracket to hold it in that position. It is then a matter of adjusting each spring nut so that the dial guage indicates the same measurement when its pointer is adjacent to each spring. On the guage below a full rotation of the pointer is 1mm so the plate is about 0.2mm square, which I think is OK.

You will find that there is a raised 'pip' on the bottom of the spring cups and also on the underside of the nuts. These 'pips' are suposed to engage with the end of the coil springs (by that I mean the end of the wire coil) ad they stop the nut unscrewing. The spring tends to locate itself with the pip at the bottom of the cup but the nuts may need to be rotated a bit more, or less, to locate the pip. You may find that, having adjusted a nut, if you re-engage the clutch and spin the clutch over with the kickstart the pips will align with the springs ends.

On the question of primary case oil I use an F grade Automatic Transmission Fluid (ATF). It is important to use the 'F' grade as this type does not have additives that will make the clutch plates slip.

Good news is that the work on the gearbox pivot has worked great. Took the 'T Bird' out for a 50 mile ride and the chain remained correctly adjusted.