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Navi pre 1964 gearbox mods

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Navi pre 1964 gearbox mods

Posted by Andrew Wibmer at April 08. 2017

I am starting to put the gearbox back together, given that a new layshaft bush is inserted and pegged in place, a shim is used between the kickstart pawl and first ( I think it is first) gear, are there any other mods worth making or things to watch out for. Was also thinking of putting a level plug in a more useful place but not done yet.

Thanks

Andrew

Re: Navi pre 1964 gearbox mods

Posted by patrick_mullen at April 08. 2017

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.

Re: Navi pre 1964 gearbox mods

Posted by Andrew Wibmer at April 08. 2017

Previously patrick_mullen wrote:

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.

Hi Patrick,

not so much thorough as there was one - well two which might be ominous.. already. I understand it is only necessary if it jumps out of gear. I never saw this bike run so trying to give myself a fighting chance. The layshaft bush clearly had spun in the case, but not too much damage was done so a new bush plus peg and a little loctite should see it ok. The current shims are 20 thou each. Not sure how the shim size is arrived at but planned to start from the same point and see what happens. Thought I might fit an oil sight window to help prevent oil shortage, but there are many small improvements and the bike has not turned a shaft for a few years so need to get a wriggle on.

Re: Navi pre 1964 gearbox mods

Posted by John Pullen-Appleby at April 13. 2017

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?

Re: Navi pre 1964 gearbox mods

Posted by Andrew Wibmer at April 14. 2017

Previously John Pullen-Appleby wrote:

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 John,

Interesting idea about the needle race, did you have to modify the shaft and crankcase to take it? Re the shims, this is apparently only an issue if the bike jumps out of first gear. I can find no info re the size etc, but will suck it and see - perhaps adding shims until the bike stops jumping out of gear. My shim was located between the kickstarter layshaft bush and the kick starter ratchet. As I get to put the bike back together I will try to determine the end float and take it up with shim if it looks too much (down to 10 thou or so) unless there is a correct figure.

Re: Navi pre 1964 gearbox mods

Posted by John Pullen-Appleby at April 15. 2017

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?

Re: Navi pre 1964 gearbox mods

Posted by Andrew Wibmer at Sunday 18:23

Previously John Pullen-Appleby wrote:

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?

 

Hello John,

I have not had the pleasure yet as am a bit busy with other things, but I tend to leave this kind of thing for a while and ask as many as I can. Re the "grunting" fit, that is a very good description of my efforts to get the old one off, a really really tough pull with a bearing puller almost destroyed the puller, shaft and bearing despite the heat. One piece of advice given by Robert Tuck "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." does it for me. I bit reluctant to remove too much but such a tight bearing must affect the bearing. FYI the Timkin bearing on the other side of my shaft was a bit of a loose fit to the extent that it had clearly been spinning on the shaft at some time. Begining to wonder if a little less of a tight fit with any discrepancy (slight) being taken out with loctite bearing and bush goo would not be such a bad plan. Thanks for the info on the needles by the way. I am interested in exploring a similar solution to a damaged little end on my conrods.

Re: Navi pre 1964 gearbox mods

Posted by andy_sochanik at Tuesday 00:07

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

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Re: Navi pre 1964 gearbox mods

Posted by John Pullen-Appleby at Tuesday 19:54

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.

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Re: Navi pre 1964 gearbox mods

Posted by andy_sochanik at Thursday 15:55

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

Re: Navi pre 1964 gearbox mods

Posted by andy_sochanik at Thursday 15:57

here is Pic1

(I seem unable to load 2 pictures..)

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Re: Navi pre 1964 gearbox mods

Posted by andy_sochanik at Thursday 15:58

here is pic2

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Re: Navi pre 1964 gearbox mods

Posted by Andrew Wibmer at Thursday 21:23

Previously andy_sochanik wrote:

here is pic2

 

thanks for sharing that, horrible image - makes the point very well... reading John's comment re using a needle bearing made me wonder why the original ones were spinning, seems a very common problem and can only be due to the bearing picking up on the layshaft - due presumably to lack of lubrication. So thought I would try a needle bearing. I found a needle bearing here: http://simplybearings.co.uk/shop/advanced_search_result.php?search_in_description=1&keywords=B-1010

There is a cheaper bearing with half the number of needles but for the extra fiver or so I went up a step. I had to grind an oil hole on the outer case but packing the bearing with grease and being slow and washing out well, the job was not that tough. Just need to make the old bearing into a thrust washer. I will fix the needle bearing with loctite bush and bearing - it is not a shrink fit, but then nor is my replacement bush. Might not be an improvement though seems to be worth a shot.

Andrew.

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