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MK111A top gear problem

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Hi there, I'm after a bit of help on what seems a weird problem, either that or total

senility has set in. I changed the alternator, went for a ride and couldn't get top gear, no problem I thought, I haven't indexed the gear lever properly. Changed it but still couldn't get top

i have pulled the outer gearbox cover off to make sure all was good in the box itself but can't get top there, goes to third and then comes up solid when you try to go further.

i have had the bike for 25 years and never touched the gearbox, never had any issues, all was working perfectly when I put it on the bench for the alternator swap so ?

am I missing something really obvious, it's as if the camplate etc in the box is not indexed correctly, but that's impossible without dissembling it?

Any suggestions?

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I don't have a Commando and the only left hooker I have is a Rudge , but first of all did you change anything about the gear lever travel when you took the case off?.Is the primary chain too tight? Did you have the clutch off?.Does the gear lever return properly after the change?.Don't worry about senility ,lots of experience here on this site to guide you.

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Nope, the only thing you can alter with the gear lever is its position, which can prevent you from selecting first or top if you get it wrong, first thing I checked and it's fine, took the primary off then and tried to select all gears straight off the cross shaft, no go, I should mention the bike was on a jack and the back wheel being rocked for all this, gearbox outer cover off next and screwdriver on the quadrant? That pivots on the inner case, still no top gear direct from the box. I'm just having trouble believing it could shit itself while sitting on the bench. The clutch wasn't touched and the tensioner is hydraulic, no play in the clutch basket, so no joy there one of the the reason I pulled the clutch outer cover off was to replace the springs there, in case it wasn't returning

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Hi Tim, I recently had the same issue with my 99, I changed a few bits and all is now well. Probably won't make sense to you as not logical!. Increased the end float on the layshaft so that play can be felt on kickstart after all tightened up. Stoned mainshaft gear and shaft spline to remove almost invisible rough surfaces which were jamming the sliding action of the gears. polished the camplate track and plunger, adjusted pawl spring to give clearance to pawl,changed clutch spider to rectify end loading the sleeve gear, new bush in kickstart ,locktited selector fork spindle .New primary chain and oversize clutch drum rollers, new clutch springs set up with dial gauge.Hope you don't have to go this far!!.

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Hi Robert, I'm thinking now it has to be something like the plunger jamming in the camp late track, it's not as if it's trying to engage the gear, it just comes up rock solid after third. off with the inner cover I guess, any recommendations on bush, bearing etc replacement while I'm in there, bearing in mind the box has never been disturbed

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Hi there again people, if I may annoy you one more time.

i pulled the inner case off and all gears are there, case sat back on the bolts its fine, when I do up the main shaft nut I lose top, soo, am I correct in assuming that it may be a problem on the clutch side of the mainshaft, even tho there is no end play in the mainshaft/clutch either end and it has been running like this for a while with all gears?

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Previously tim_plunkett wrote:

Hi there again people, even tho there is no end play in the mainshaft/clutch either end and it has been running like this for a while with all gears?

Hi Tim

Did you possibly over tighten the rear chain while it was up in the air? That would be my clutching at straws offering.

As you say very strange that this should coincide with an alternator swap, did you changed the rotor and the stator, if you changed or removed the rotor, how did you lock the crank to torque the nut ?

My guess is that either, the circlip behind the clutch has moved or that one or more of the bronze bushes in the sleeve gear has moved .

As you say you have owned the bike for 25 years, without making the acquaintance of the gearbox internals, it's about time you introduced yourself! Before the layshaft inner bearing forces the occasion;0)

Seasons Greetings

Katherine

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Hi tim, As Katherine says, its time, the inner layshaft bearing may not be the issue but is a weak point in this box. however I would not follow common practise with a roller replacement and the shimming issues that go with it, instead do as Hemmings says. I think for now you should focus on solving your selection issue first otherwise you could end up with a re-assembled refurbished box that still won't find top!.Been there ,done that.Would be worth pulling the layshaft out for a peek at the end bearing just to check its still working ,then pop all back till selection issue sorted.If you cant work the quadrant thro all the gears while revolving back wheel then its pointless putting the outer cover and all its gubbins back on.Its easy to loose the quadrant timing with the inner cover off if you move the quadrant too far. Look thro the camplate track to see how teeth engage before you loose it, Got to go now,more later.

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I thought I remembered someone suggesting slackening / removing the cam plate plunger? You can remove it without disturbing anything else and that would eliminate that as a source of the problem.

For top gear to engage the sliding dog needs to move along the mainshaft towards the sleeve gear / clutch but if there's no movement past the 3rd gear position this would suggest that either the quadrant is fouling something, the sliding dog is not sliding freely, or the sleeve gear is displaced towards the RHS of the gearbox. The fact you can engage top with the inner cover loosely fitted would support the last theory.

I can't see how the layshaft bearing would have any influence here as top gear is effectively direct drive with the sleeve gear locked to the mainshaft.

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If the quadrant is moved past its normal range you can get it to foul something. If there is a slack bearing or bush the shafts can move sideways making issues with gears sliding in /out of engagement.worth taking the plunger out to check for free movement ,spring,hydraulic relief hole ,condition of nose etc.Do remove gears from mainshaft and take a really close look at spline surfaces on shaft and in the gear, mine were rough sticking and tightspots..Bent selector?. Issues can be hard to spot and even the countrys best expert said its a wonder the box actually works!.

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I've always thought the Norton box one of the best around in all its incarnations from the Doll's Head to the Commando. Certainly better than the awful Burman things as fitted to my Ariel Arrow (with a free neutral between each gear) or my brother's Ajay Model 18. And much slicker than any of the BSA and Triumph offerings.

In my experience anyway.

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HI Ian,I also think its a great box too,just lacking in developement for double the power it was designed for. It only taken me 20 years to find why one box is a great one (Atlas) and one a poor one (99).But thats not the boxes fault.The real experts don't tell all the secrets.Only recently found the way to a non dragging clutch from an old Manx Norton racer who had to run and bump.I can't manage that on the flat with my 250 single.

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Do tell!

I remember with my first Norton 45 years ago (1947 16H) the main problem was a worn thrust washer on the mainshaft allowing the clutch to move slightly when lifted.

On the other hand, the mushroom thrust pin was superb giving nice straight lifting of the pressure plate.

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The clutch can benefit from having less room to wobble when lifted as this allows the edges of plates to snag inside the drum. This makes drag ,very unhelpfull if it brings the piston up against compression on a HC MAnx! let alone a 250 Mach1 motor.I have swopped the std rollers (3 thou clearance) for some plus1 thou rollers which gives me a bearing with 1 thou clearance. I bought a pack so if someone wants to try it they can buy a set from me!. I have a mushroom head radial needle roller clutch lift conversion for the 99 lined up next time its down.

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I'll remember those rollers although it will be a while before I dive into the ES2 clutch.

Will the radial bearing make much difference especially if you have a ball between the pushrod and the lift pin?

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Hi there people, thanks for the input, what I now suspect is happening is this,

when I went to undo the mainshaft nut it was marginally more than finger tight,

Not that long ago I replaced the seal in the inner primary case behind the clutch, is it

possible that the mainshaft nut on the gearbox side was loose and I when replacing the clutch nut I have pulled the mainshaft out of line?

i also noticed that when presenting the inner gearbox cover that the mainshaft end doesn't

quite line up in the centre of its bearing which would suggest primary chain too tight, but it has a hydraulic tensioner so I'm ruling that out and going with u/s mainshaft bearings in the box, I know the inner case one is a bit average.

so here's my plan, refurb the box as you suggest, what does Hemings suggest for the layshaft bearing Katherine? and put it all back together, gearbox mainshaft nut first and see what happens.

what do you reckon?anything further I should be doing?

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Previously tim_plunkett wrote:

what does Hemings suggest for the layshaft bearing Katherine? and put it all back together, gearbox mainshaft nut first and see what happens.

Hi Tim

I believe Mr Hemmings recommends phenolic caged ball bearing FAG 6203TB.

Personally I went with the roller conversion endorsed by Andover Norton. I also agree with the thinking on the Access Norton site that the standard torque figure for the nuts on the main shaft is to high, and that the standard tab washer behind the clutch nut, is not much good. I replaced the clutch side tab washer with a Bellville washer and added drop of loctite on the threads at both ends of the mainshaft torqued the nuts up to 43 ftlbs, with out any issues.

Your thinking regarding pulling the main shaft through the gearbox by tightening the nut on the clutch end doesn't quite add up unless the circlip behind the clutch on the mainshaft has come out of its groove; I understand this was not unheard of on earlier models and part of the reasoning behind the reduction of the torque figure for the mainshaft nuts.

Regards

Katherine

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Previously Katherine Scott wrote:

Previously tim_plunkett wrote:

what does Hemings suggest for the layshaft bearing Katherine? and put it all back together, gearbox mainshaft nut first and see what happens.

Hi Tim

I believe Mr Hemmings recommends phenolic caged ball bearing FAG 6203TB.

Personally I went with the roller conversion endorsed by Andover Norton. I also agree with the thinking on the Access Norton site that the standard torque figure for the nuts on the main shaft is to high, and that the standard tab washer behind the clutch nut, is not much good. I replaced the clutch side tab washer with a Bellville washer and added drop of loctite on the threads at both ends of the mainshaft torqued the nuts up to 43 ftlbs, with out any issues.

Regards

Katherine

Thanks Katherine

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The mainshaft nut does need to be tight. Most gear selection problems in my opinion are spring related ? Could it jus tbe bad luck that fiddling on the stand had provoked the greenstick fracture in the pawl spring that usually occurs sooner or later ?

No corrosion problems on the pawl carrier ?

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If you can't get top gear by working the quadrant direct with the cover off then the issue is not likely to be in the outer cover(although it usually is!). Hemmings has been building (and racing) boxes before most of us were old enough to ride so I would not discard his advice too soon. The roller mod introduces a lot of end float that is usually dealt with by moving half the gears in the box up to 50 thou out of their normal position, this seems unwise to me, although it usually works.

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Hi, interesting thread as I have just rebuild my Mk3 gearbox and I have a couple of points to add to the pot:-

Layshaft roller - I bought the roller supplied by AN and I thought that I would have to shim the layshaft end as per the various American notes on the subject. But, when I tried that and measured everything there was no shimming required. I thought that maybe the bearing outer was not fully located in the housing or the new K/S bush I had fitted was sitting proud, but no. In fact, I milled a few thou off the K/S bush to give a few thou end float on the layshaft. This can then be felt as end float on the K/S shaft when assembled. The AN product comes with no shimming warnings but I should have asked them if that is how they have designed it.

Loctite on torqued threads - a few years ago I rebuilt a Manx cambox and carefully loctited the nuts that are torqued to hold the cams to the drive gears. After the first ten minutes of running at Mallory I had a major cambox failure and several broken parts. An experienced engine builder came over in the paddock to help and I told him what I had done in the recent rebuild. As soon as I mentioned the word loctite he knew what had gone wrong. He explained that when you tighten a dry, loctited thread it will quickly grip on the thread BEFORE that torque has been applied to the bearing/shaft on which it is acting. In use, the nut will not move but the bits underneath are NOT under the full torque and they will move. Hence, always oil a thread to be torqued. Expensive lesson, but one I am happy to pass on. (I think, Katherine, that your use will not cause a failure/problem on your mainshaft, providing there is enough torque to stop the bearing inner rotating on its shaft?)

Norm

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Previously tim_plunkett wrote:

i also noticed that when presenting the inner gearbox cover that the mainshaft end doesn't<quite line up in the centre of its bearing which would suggest primary chain too tight, but it has a hydraulic tensioner so I'm ruling that out

There's always a bit of play in the drive side sleeve gear bearing so that often gives the impression that the shaft is out of line as even with the correct primary chain tension there's enough to move the shaft slightly, and of course this is exaggerated at the right hand end.

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Hi Tim, Please keep us informed as to progress , I spent a lot of time and money to cure finding neutral and stiff selection issues ,never really being certain what was the clincher,just being happy with the end result. A bonus is after all the work I now have a wonderfully light smooth grippy clutch that can be pulled with one finger . Happy to keep fighting the primary oil leak as perfection is just too boring!!.

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Loctite on torqued threads

Not wishing to hijack this threadsmileyI have started a new one titled imaginatively:-

Loctite on torqued threads

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So update, I think I have the problem, the quadrant retaining bolt was missing, the quadrant has a casting flaw giving it a lip on one edge, the quadrant has moved into the box ang this lip is binding on the camplate.

i removed the clutch etc and the problem remained, with the mainshaft nut torqued I still had end play in both shafts.

the rest of the box with the exception of the inner case mainshaft bearing appears to be in excellent condition, probably something to do with the bike doing most of its miles in the NT and top of WA where roadhouses are 200/300 kms apart so not a lot of gearbox use.

Attachments IMG_1865.JPG
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Previously tim_plunkett wrote:

So update, I think I have the problem, the quadrant retaining bolt was missing,

Hi Tim

Good find, there is no substitute for terrier like tenacity when it comes to fault finding.

Regards

Katherine

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Another one for the records,not seen that before, from your earlier comments it had to be the inner workings ,and happily a very easy fix, you are a lucky guy!!.

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Loctite on torqued threads:

Tony has picked up on my comments above and he is exactly right to question my view that its use is inadvisable on torqued threads. Industry regards it as a lubricant and that dry torque figures may have to be reduced by 20% in some fittings.

I offer a big apology to Katherine for suggesting she might have been in error in using loctite on the gearbox mainshaft nut.

Norm

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Hi Norm

No apology required, I would like to believe that whenever, any member offers advice it is done with the best intentions, with esprit de corps in mind; Sharing knowledge gained from personal experience.

After all is said and done it is advice a suggestion, not an order!

Anyone for a Loctite and tonic, or are we staying dry for Christmas! ;0)

Best regards

Katherine

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Just on loctite, as someone who has done a million miles on old pommie bikes, when they weren't old, and were, I personally think loctite should be supplied in 20 litre drums and free, a contribution to the mental health of old farts like myself

 

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