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Navigator Gearbox Leak.

Submitted by philip_rawnsley on Wed, 25/09/2024
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Light Twins

Hi. I recently purchased a Navigator and on inspection I've found a few oil leaks (what's the problem, that's normal I hear you say). One being from what appears to be from the gear selector, between the gear selector lever and where the gear indicator marker protrudes from the middle of the lever. Is there a seal in there, is it just worn, it is leaking quite badly from there. I don't have a manual that shows this area in detail, is there one? And, I don't want to go ripping into it if there's an easier fix. I've attached a picture that hopefully helps to explain where I mean. Thank you

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Submitted by ian_soady on Wed, 25/09/2024

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... is pretty sketchy at the best of times and lacks exploded diagrams of many of the important bits. However, there are O rings on the ratchet plate spindle which may be the source of your leaks. There are also O rings on the kickstart and gearchange spindles which can be exchanged for X ring type - I'm currently corresponding with Andy Sochanik re alternatives here.

You can get a photocopy manual from the club or from BMS at the National Motorcycle Museum.

Hi Ian. Thank you for your reply. I'll strip it and take a look, hopefully it's what you suggest.  A manual did come with the bike, but it is very basic and doesn't show much, especially the gearbox section, it shows a grainy exploded gearbox with all the parts numbered but no key to the numbers. The kick-start is dry, the only leak on the box is from the middle of the selector. Regards Phil

Submitted by peter_holland1 on Wed, 25/09/2024

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Hi Philip, 

The gearbox on lightweight twins often leaks slightly as you have found out. I don't know the year of yours, but in 1964 the gearbox oil level plug changed position. 
The oil must be kept up to the level hole. 
​​​​
​​At this level the layshaft and kick-start shaft are half immersed in oil and the critical layshaft bushes are lubricated. 

I fear that your 'not leaking' kick-start spindle is merely a sign that your gearbox oil level is too low. 

I recommend using 6mm x 2mm o-ring in the gear indicator spindle. Two required. These have a 10mm outside diameter and are a good seal. Those from NOC are the imperial size and sealing can be a bit marginal. 

The square section seals from NOC are good for selector shaft and kick-start. 

Peter

Submitted by philip_rawnsley on Thu, 26/09/2024

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Hi Peter.
 Thank you for your reply. Do you happen to know the part numbers for the square section seals, as i can't find them on the shop site. Many Thanks

Quad seals for kick-start shaft and gearchange shaft are the same. 

NOC part number 040006Q

Submitted by tony_ripley on Fri, 29/11/2024

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Hi Philip,

Did you stop the leaks?
I have just replaced the seals and now the only leak still showing is the same as your, from the indicator shaft. I had replaced the seals with the NOC shop ones. The shaft certainly was an easy slide into the hole so did not give me a lot of hope that it would seal.
I have just ordered some of the 6mm x 2mm O-rings suggested by Peter.
But it would be interesting to know if yours has stopped leaking.

 

Hi Tony. Only got round to working on it over this weekend, and yes the gear selector leak has stopped leaking by using Peter's recommended seals. However, even though I used the square section seal on the kick start shaft, it's still leaking more than the Amoco Cadiz, so back to square one with that. Beginning to lose the will to live with this one. Can't find the correct spider for the clutch either, so had to use the butchered old one, not sure how long that'll last, hopefully until a replacement comes along.  Anyway, I hope you get yours sorted. 

Hi Tony. Yes, I meant X ring seal. Will strip it down again once I get rid of this virus and have a thorough look.  Only just got the clutch side back together, leaks from that side too, but still looking for a spider for the clutch though, as a previous owner really mullered this one, but hoping that even though there's a slight wobble on the clutch unit, that it'll do until I find one. Regards Phil

Checked and they have 19.1mm splines so look like the bigger ones at 3/4". I was about to post that on here.

Submitted by john_crocker on Fri, 29/11/2024

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My Navigator didn't so much leak as pour oil from just about everywhere!
The indicator shaft made a good contribution to the mess under the bike.   My solution was to blank off the gear lever shaft and shorten the shaft appropriately.  I think the gear indicator was a gimmick with almost zero function.
I also modified the gearbox cover so oil seals rather than O rings could be fitted.   
So far, no leaks from the gearbox cover.
 

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Submitted by ian_soady on Tue, 17/12/2024

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... I used quad rings from Simply Bearings (ref Q4114) and 6x2mm O rings for the indicator shaft as suggested by Peter. Filled with oil yesterdays and no drips. We will see how it performs when I eventually get it started up!

I have only done about 25 miles so far but ... drum roll ... I do not have any leaks from anywhere!

It was leaking from the primary chaincase where it had distorted slightly as a result of welding up the cracks caused by the footrest hitting it hard sometime in its life. Now flattened and not leaking.
It was leaking from the kickstart shaft oil seal, new X-ring seal fitted and not leaking.
It was leaking from the gearchange shaft and gear indicator shafts. Gearchange shaft, X-ring. Indicator shaft, metric O-rings. really difficult to fit as it was very tight.
No leaks!

I have also fitted an in-line oil filter. will cover that in another thread.

Also, with electronic ignition and a brand new Amal Premier carb, it is a first kick starter and ticks over nicely. I still need ear plugs to keep out the rattling but that I can cope with.

So all ready to ride just in time for winter.
 

 



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