Spongie gearbox on an 16H

Fix draggy clutch?, adjust pawl spring shape,check if roller bearing conversion working freely if fitted.check case bearings for free runnig.

Previously wrote:

Fix draggy clutch?, adjust pawl spring shape,check if roller bearing conversion working freely if fitted.check case bearings for free runnig.Adjust tight or loose chains.

Which gearbox do you have ? If it's the "Doll's Head" then wear in the external linkages won't help selection. Earlier return spring cover plates do not include a bush and provide little support for the pawl carrier which then becomes a rattling fit in the outer cover. This allows the shaft to twist rather than transmit the correct motion to the selector.

The most likely point of wear inside the box is the bronze thrust washer which locates next to the sleeve gear. This will also make for poor selection.

It's a straightforward geabox to dismantle.

Paul, what do you have in terms of literature ? The wartime 'Maintenance Manual and Instruction book' is pretty good on the gearbox. A copy of Edgar Frank's book is handy too.

With regard to the external control rod, the manual simply says that the clevis pins should be free when top or bottom gear is engaged.

My suspicions remain with the bronze thrust washer. I believe that Andy Molnar sells them, hidden away on his lists between the stainless stuff.

It's surprising what some people will put up with on a gearbox. It's quite a nice box to use when in good condition - the travel is long and it doesn't like to be rushed too much but it should be precise.

I wouldn't worry too much about oil leaks. Neither engine nor gearbox has what we would now call 'proper' oil seals and if you don't have the odd drip from the tappet or magneto cover drain then they must be blocked !

The 'Doll's Head' really is a pretty straightforward box and provided the problem is wear and not due to the previous owner having done something that's difficult to spot then I'm sure that the problem will be obvious.

Andy Molnar is well know for his stainless parts and his Manx Racers. Strangely, the thrust washer is hidden away in the list of stainless parts - Have a look at the pdf for Norton singles on this link :-

http://www.manx.co.uk/pricelists/pricelists.htm

Hello

Ken MacIntosh in New Zealand has needle bearing thrust washer and shims that he sells that replace the bronze thrust washer and you again have to worry about wear in this area. He also provided me with a very nice write up on these old gear boxes and their various ills. I am sure if you rang or wrote him he would provide it to you also. The next time I speak to him I will ask about sharing it around or posting on the web site.

I am not so sure that the worn bronze thrust washer would cause sponginess. As it wears it takes more and more clutch adjustment to get the proper clutch disengagement and poor disengagement would make harder gear selection.

You did not describe the condition of the holes in the two external levers, if the pins were worn, then most likely the holes are too. Cleaning these up and fitting bigger pins will do the trick. The pins use on the check springs for the front forks will often work.

Make sure the detent spring and follower are in good shape and not worn flat or have collapsed spring.

Make sure the positive stop mechanism is firmly fastened in.

Have you check your outer cover where the gear change shaft comes through? Is it oval shaped indicating wear caused by the positive stop and selector shaft moving around.

Check and see how much wear there is on the gear change spring and the pillars on the stop plate that hold it place. They may be worn and won't allow the ratchet mechanism to center properly.

Anyway, if you do bearings you can used sealed bearings on the drive side either running with both seals, or removing the inner one, this will help reduce oil leakage. Also the quadrant shaft, can sealed better, through the use of and o-ring. One must polish the side of the lower splined lever and perhaps make a longer bush to help control the crush on the o-ring so not to cause to much drag when changing gears.

Regards

Mark

Previously wrote:

Dear Paul, if it is any consolation to you I have a 1947 Big 4 with an upright gearbox which is virtually identical to the dolls head that preceded it. I have exactly the same symptoms as you describe. A very inexact and unpredictable gearchange. The lever tends to stick down and then when pulled up a bit and pushed down again it has changed 2 gears and not one. I've replaced the ratchet plate and the bearing that holds it to remove the wobble in the gearchange shaft. I've got oversize clevis pins in the external linkage to take out the slop. I've changed the bearing in the cover and I've changed the kickstart shaft which carries the other shaft. When I just heave on the lever sticking out of the box it selects gears just fine but when I couple up all the linkage and adjust as best I think it should be then the gears select in the 1st to 4th direction but still don't want to come back.I can not get first gear at all. It is just as if the ratchet mechanism isn't working engaging properly. However the pawls are perfect. The spring was weak and I've replaced that too. This is driving me mad. I shall take the box out of the bike this weekend and do a complete dismantle and inspection but I strongly suspect the problem isn't in the box proper but in the nd cover and ratchet arrangement. Looks simple but its has got me beaten. Clutch is fine.

Regards John Clement Melbourne Australia.

Hi Mark

Kens from thefrom the land of my wife she is a Kiwi!!if he can help thatsgreat...Thanks for the advice .

I will run all the advice Via my Mate who is the best one to read it and make sense of it all as he does that sort of thing but mostly to Triumphs.. I have changed the pins in the gear change outer rod as they were worn and now they fit a lot better but still have enough movement to select ok. The clutch was renewed by the previous ownerand we did have to mess about with it and adjust the clutch worm screw a few times to get a decent clutch .

If you can post anything that would help as Richard did that would be great !

Iam away from 2mrw to Spain for a week so i will have a look at any further info when i return. Once again thanks Guys its all a big help !!

Some information that may help Paul's type of shifting issues.

The manuals for Norton gearboxesall ignore the basic problemsof making these type gearboxeschange perfectly at racing speed.The standard gearboxwith a lever about a foot long is very forgiving as this encourages slow gear changing.

The basic problem is the lever at the top end of the link-rod is following an arc in line with the bike, and the lever at the lower end of the link-rodfollows an arc at right angles to the bike.

This works OK by having enough clearance in the clevises (the very early bikes have a superior double clevis in the top joint),but worse is the fact the four gear positionsof the camplate are equally spaced, as are the four positions of the positive stop mechanism,but the lever and rod system connecting them is essentially a'toggle'.

This means the pedal movements are equal, but the cam platemovements are certainlynot! In typical Nortonmanner they make this still work well! This is because the stops in the foot change mechanism only actually work correctly in 2nd and 3rd gear, as the limit to movement in 1stand 4th gearsare the gear selector pins hitting the end of the cam plate grooves, not the foot change stops, so the over changing caused by the toggle effect does not matter.

Because of this, the link rod should be adjusted by putting both the upper and lower levers in 2nd gear positionand adjusting the rod length so the pins slidein freely. Then move the pedal to 3rd gear position.Remove the lower pin and make sure the cam plate and the foot change detent plungers have 'clicked' home. If you are lucky the holes will still line up and the pin will push in and out easily. If the movementisslightly too little,this is OK, and the rod shouldbe adjusted so the gearbox slightlyunder changes in both directions.

This is much better than over changing, as the inertia will carry the cam plateinto the correctposition. If you cannot get this to work as suggested, you may need to restrict the throw of the positive stop mechanism. As standard this is done by the ratchet plate in the positive stop hitting the pillars that hold the springplate.

If the gear pedal centralizing spring is removed, the plunger in the back of the positive stop will hold the ratchetplate in each gear position.The travel of the ratchetcan be changed by buildingup the rather flimsy tips of the fan shaped ratchet plate with bronzeweld, and then grinding them back until themechanism slightly under-changes in the 2nd to 3rt1 and the 3rd to 2nd changes. Also check the pillars for wear on the 'stop'faces.

It is also essentialto make sure that the ratchet is centralizing correctly. This is the job of the pedal spring.

The gear pedal spring is often the cause of gear changing problemsand a new one often doesn't go straight in and work correctly. The common faultsare when you push the pedal and the lever doesn't centralize. so that when you push it again the pedal just goes down, withoutchanging gear. Also the pedal has a dead spot' in the middle.

Both these faults are fixed by bending the spring legs where the legs push against the stop plate. If the plate isworn where the spring seats, a repair with bronze welding works well. Because the spring must touch the retaining plate in two places,and touch the two stop pins on the ratchet plate at the same time to avoid a 'dead spot' it may be that one leg needs bending, but at the same time you needto checktheratchet claws are equally spaced (central) on the ratchet plate. This is also fixed by bending the spring legs. Do this by holdinghalfthestraight part of the leg in a vice using "soft-jaws" and tap the overhanging part with a small hammer. It will bend quite easily.

Don't turn the spring over after bending the legs,as this will ruin all your good work by offsetting everything the other way! I mark one leg and one pillar with paint. If the spring is goingto break in service, it willalways do so where the straight legs meet the coils. Beware of any rust pitting in this area. The dolls head springhas one completecoil,thelay-down type two.

FWIW

Mark