Navi pre 1964 gearbox mods

Hello Andrew,

You are being extremely thorough. Why did you fit a shim in first gear? Have you some special plans in mind for usage of the bike? I ask this as normally you would only insert a shim here if the gearbox jumped out of first gear. I had a Jubilee which jumped out of first but it quite happily pulled off in second until I eventually got round to shimming it.

Certainly check it over when it's convenient on the bench but they are reasonably robust and fairly easy to work on even when fitted back in the frame. Gearbox blow-ups were mostly caused by the owner not checking that there was oil in the gearbox and oil leaks are the hardest thing of all to stop.

Patrick.

Hello all,

My Navigator had spun the layshaft bush--I have replaced it with a needle race--cut the head from the bush to act as a thrust washer. I have not assembled it yet but will do so shortly. I plan to investigate the whole shims bit as well---what is the story here?

Hello Andy,

There was no need--the shaft diameter if 625 (5/8) and the OD of the needle race (the ones BSA unit singles use for the job) was a close enough fit in the worn hole to be loctited in place. |I think the bush was one made to replace one that had been spinning (it had been doing it as well) as it had no peg or any means of holding it in placer. I cut the head off the bush and pegged it into place as a thrust washer--the needle race should protrude a couple of mm from the face for the washer to sit on with a 2mm diameter silver steel peg to stop it spinning .

I have just tried to fit the crankshaft into the new main bearing in the timing side--I say tried as I have given up for the night as it would not go all the way in. I eased the shaft with emery but it still does not want to know. The says they should be a 'grunting' fit. This better describes my comments I think. Has anyone else had this experience?

Several points here...

1) Love the idea of a needle roller for the layshaft, and leaving a thrust washer in place as well - ensure its pegged to prevent it rotating!

2) The main bearing may not be fiiting on the crank as it may not have had its radius relieved. Did you get the correct bearing from the NOC? Did you fit it the correct way round? The Dominator has a 0.090" radius to contend with where the journal meets the crankcheek, & most bearings are ground to match this. The Lightweight twins employ a 0.125" radius there instead! Beware!

3) Shimming between the 1st gear & kickstart crank. You need shim(s) if (once the gearbox is assembled) you can push/pull the kickstart assembly into & out of the gearbox. Look at it another way... if you detect movement there, it means the 1st gear has that much movement inside the gearbox, allowing it to jump out of engagement with the gear next to it. Your task is to minimise, by shimming, that very movement

Andy S

Attachments
main-bearings-chamfer-pdf

Hello Andy, Andy--and Patrick!

The timing side bearing was indeed one from the trusty spares scheme--I still cannot get over the magnificence of this institution--bravo lads!

It is a Timken race and really ground out--far more so that the one it replaced--it even had ground for lightweights written on it--I put the taper facing in.

"The late very practical John Hudson of the Norton service dept advocated rubbing down cranks to allow the bearings an easier fit .A very tight bearing can loose its internal clearance and wont last." I followed the advice the late Mr Hudson and all went well. The crank and cams rotate as smooth as silk. I did find that the centre of the drive side roller was the sort of fit that that has cost me a lot of money getting Triumph cranks chromed, knurled and all sorts. I was happy with the race so I did not disturb it.

It was initially unwilling to enter into the out ring until I headed it to about 120 degrees (I have bought new triumph one that I was told to expect this--only enough heat that a hair dryer can provided, but reluctant cold--they work fine by the way).

When had to split the cases again to rectify the cam situation--I was lucky--the gasket survived and the crank pulled out of the timing race--fine by men--it is bolted in there in used.

The manual Andy--The Twin Cylinder Manual (for all twins--I have never owned a large Norton twin but--I think they have one camshaft--it says--on page 33 ' Fit the camshafts with their springs and plungers the exhaust drives the contact breakers'. The annoying thing was that--I had it right but looked in the manual one last time and changed it--still no harm done.

I'm glad to hear about the gearbox--here is even a picture of it being built prior to joining the cases.

I'd be a bit careful trying to deploy needle races in the small ends--just in case the require larger diameter holes are too large. I have hear of many people putting buses in Enfields, BSAs and 750 Triumphs to escape ravaged small ends. You are right of course Andy--pinning is a must. My case showed signs of wear and it looked as if the original bush was pinned (remains of a hole--difficult to see in my dreadful pictures)--spun and the person making the new one did not bother and it spun again.

MY thrust washer looks awful as only the third hole I drilled was the proper diameter--there are two others plugged with phosphor bronze.

I'm not that bothered as new thrust washers have holes, slots and all sorts to help oil retention. It is a mess under the thrust washer but--it sits well and--when I got the bike--all gears seemed to work.

Attachments
IMG_5006.JPG
IMG_5008.JPG

Pictures very indistinct - but the damage in the 2nd photo can be imagined. If a spinning bush is left to its own devices, it can wreck the gearbox casting - thus the whole crankcase....

Here is an unmolested bush - note that there is no peg to stop it rotating.

Here is a picture of a damaged case - with my suggestion for moving the breather

here is Pic1

(I seem unable to load 2 pictures..)

Attachments
broken-cases-jpg

here is pic2

Attachments
g-box-early_sleeve-gear-jpg

Previously andy_sochanik wrote:

here is pic2

Hello Andy and Andy,

I notice in the picture of the unmolested bush that the bush seems to be flush with the gear casing. Mine--that has admittedly been shamelessly molested stands proud. Could this locate the layshaft on the wrong place as regards the kickstart ratchet. If my thrust washer did sit in a recess and was level with the case it would be below the level; of the roller bearing that the sleeve gear lives in.

Andy W--you mention an oil hole--what is this? Where a forerunner of my last bush had been spinning round it had seemed to have destroyed what I took to to an attempt at lining it. Are you to referring something that lets oil into the bush from the case. Needle races have quite generous tolerances and--the bronze thrust washers (in this case old bush heads) only need a groove cut in the face to let gear oil in.

Cheers

JPA

Hi John,

You make 2 points:

1) The bush at the back, originally unpegged, can rotate in its housing and cause a lot of damage - as you saw in the other photo. The bush is not quite flush with the casing - but it is pretty close. I don't have an accurate measurement for you at present - hope to return to this subject later (in another posting). The Layshafts position in the gearbox will be moved if your bush is 'well raised'. The only way the ascertain if all is well (or not) is to loosely assemble the sleeve gear & mainshaft plus layshaft & fixed gear (at the far end) AND 1st gear (nearest to you) into the gearbox & see if you can fit the inner cover (with the kickstart fitted) over it - do up the nuts constantly checking that the sleeve gear can rotate freely. No need at this stage for any other gears or selectors. If the shaft binds, then you know you have trouble.

Some of the gearwheels are fixed in place by the shaft, and some are held in place by the selectors. The shim you mention is fitted between 1st gear & kickstarter to take up any slack (in & out) on the kickstarter. It may be that you have reduced (or eliminated) the slack - or sadly gone too far and causing the layshaft to bind now.

2) The oilway to the bush is clearly visible in the photo. It is above the bush & angled down at 45deg - & drilled right through it. Oil is thus delivered direct to the layshaft. Sadly, an unpegged bush can easily move round, thus blocking this hole & causing issues.

Previously andy_sochanik wrote:

Hi John,

You make 2 points:

1) The bush at the back, originally unpegged, can rotate in its housing and cause a lot of damage - as you saw in the other photo. The bush is not quite flush with the casing - but it is pretty close. I don't have an accurate measurement for you at present - hope to return to this subject later (in another posting). The Layshafts position in the gearbox will be moved if your bush is 'well raised'. The only way the ascertain if all is well (or not) is to loosely assemble the sleeve gear & mainshaft plus layshaft & fixed gear (at the far end) AND 1st gear (nearest to you) into the gearbox & see if you can fit the inner cover (with the kickstart fitted) over it - do up the nuts constantly checking that the sleeve gear can rotate freely. No need at this stage for any other gears or selectors. If the shaft binds, then you know you have trouble.

Some of the gearwheels are fixed in place by the shaft, and some are held in place by the selectors. The shim you mention is fitted between 1st gear & kickstarter to take up any slack (in & out) on the kickstarter. It may be that you have reduced (or eliminated) the slack - or sadly gone too far and causing the layshaft to bind now.

2) The oilway to the bush is clearly visible in the photo. It is above the bush & angled down at 45deg - & drilled right through it. Oil is thus delivered direct to the layshaft. Sadly, an unpegged bush can easily move round, thus blocking this hole & causing issues.

Thanks for this Andy

My thrust washer is the head of the old bush. The bush in question seemed well made but was loose in the hole (while bearing no sign of picking up) there was also no plug sealing the back of the hole. I am assuming that this bush ran long enough to get loose in the case. It had no oil hole but I now realise that a predecessor of had one. I shall check it as you suggest--none of my gears appear to b fixed on the shafts but the way.

All the gears worked when I got it but how I do not know. The nut that sits under the clutch actuator was cross threaded on the shaft and when I took the inner cover out it was free to wobble.

I can make a thinner thrust washer if needs be. I have attached a picture of a BSA one--the cross cuts, I think, are to let oil into the race. Oddly, I have never seen s BSA of a Triumph, even ones that have lay-shaft bushes (c15s 3TAs) with an oil holes.

Which gears are fixed and how?

Attachments
bsa-thrust-jpg

Out of interest how do you peg the bush, there's not much room to work in there! Incidentally, my layshaft bush has the same cross cuts that the bsa thrust washer has. I remember taking out a failed bush back in the day and that had an oil way scrolled into the inner face of the bush. My replacement at the time didn't but i didnt keep the bike long after that to see how it faired.

dan

I have never pegged a bush so I can't properly answer the actual question. I have simply relied on loctiting into place and so far have never known a failure.

According to an old motorcycle mechanic who worked on these when they were current there was nothing wrong with the actual bush itself. The real fault in the design was the fact that the layshaft bush was very high up in the gearbox and depended on splash lubrication. When the gearbox was full of oil everything worked perfectly -hence all Norton tests said everything was fine- BUT if the oil level fell significantly the shaft picked up in the bush because it was running dry. Then the bush commenced spinning in the case. If totally ignored then the end result was serious damage to the casing. Pegging the bush is worth doing but it doesn't really solve the real problem.

The real problem was the user who NEVER checked the oil level despite the puddles of oil regularly left behind.

Anyway that's what I was told.

Patrick.

Previously Dan Field wrote:

Out of interest how do you peg the bush, there's not much room to work in there! Incidentally, my layshaft bush has the same cross cuts that the bsa thrust washer has. I remember taking out a failed bush back in the day and that had an oil way scrolled into the inner face of the bush. My replacement at the time didn't but i didnt keep the bike long after that to see how it faired.

dan

Hello Dan,

I used a 2mm piece of silver steel that is good fit (but Loctite works wonders). I had to be small as the bush head was smaller that thrust washers I have seen with 3mm pins. I have seen bearings with a scrolled oilway--in fact when the needle race failed on one of my BSAs as lad--my toolmaker father turned up a bush to replace it with a spiral in it

Previously patrick_mullen wrote:

I have never pegged a bush so I can't properly answer the actual question. I have simply relied on loctiting into place and so far have never known a failure.

According to an old motorcycle mechanic who worked on these when they were current there was nothing wrong with the actual bush itself. The real fault in the design was the fact that the layshaft bush was very high up in the gearbox and depended on splash lubrication. When the gearbox was full of oil everything worked perfectly -hence all Norton tests said everything was fine- BUT if the oil level fell significantly the shaft picked up in the bush because it was running dry. Then the bush commenced spinning in the case. If totally ignored then the end result was serious damage to the casing. Pegging the bush is worth doing but it doesn't really solve the real problem.

The real problem was the user who NEVER checked the oil level despite the puddles of oil regularly left behind.

Anyway that's what I was told.

Patrick.

Hello Patrick,

yes indeed--if it has oil it is quite happy

Am about to peg mine, the club bush comes with a semi circle cut into the thrust face, a 5mm bronze rod would fit nicely, is that what the cut out is for, the original bush didn't have one?