For three years I have battled unsuccessfully to cure a very notchy and difficult gear change on my Electra. I have stripped and rebuilt the clutch and gearbox, replaced the push rod, plates, springs and bearings, checked clearances and wear on the pinions and selector forks, replaced the clutch lever and cable and set the clutch clearance correctly, used Classic Castrol EP 90 oil in the gearbox and ATF oil in the primary chain case.
I have set up the clutch so it is light and doesn't slip or drag but no matter what I do the gear change has remained stubbornly difficult and the bike will occasionally slipped out of gear unless I am very positive in my gear changes. The very opposite of what a late gearbox Lightweight Norton gearbox should be.
Yesterday I escaped the home DIY mountain to check progress on curing the stubborn weep from the primary side filler cap and on checking under the bike I noticed there was a slight oil leak from the gearbox drain plug and/or what the workshop manual calls the 'cam drum plunger bush'. This is the screw in, hollow plug located in the bottom of the gearbox that holds the spring loaded wedge ended plunger which pushes into the five notches in the cam drum that positively holds the selector forks in each of the gears and neutral. Interestingly the spares book diagram doesn't show a sealing washer for the plug nor does it show or list the gearbox drain bolt or a sealing washer.
Having drained the box by removing the drain plug and 'cam drum plunger' plug I searched my boxes of copper and fibre washers to fit. Sadly they are all metric so it took a fair amount of gentle file work to get one to fit the drain plug. Far more difficult was the screw in 'cam drum plunger' plug because the thread ends about 2.5mm or about 1/8th" before the shoulder that seals against the casing. Long story short the only copper washers I could find which would fit and make a seal were 1mm thick and I needed 3 to make an effective seal. I took the added precaution of annealing the washers before tightening them up and refilling the box. Happily a fast 20 mile run this afternoon has proved that I have cured the minor oil leak.
Perhaps more important and very happily those three copper washers have obviously reduced the spring pressure which the cam drum plunger is being forced into the cam drum indents which has the gear change, making it slick, light and very positive with no sign of jumping out of gear. Success at last!!!!
I don't know the provenance of the cam drum plunger spring but I guess the original was replaced for some reason by a previous owner with a much longer / stronger spring which has been the cause of the difficult, notchy gear change. An unforeseen consequence and hidden problem of not using standard parts.
So the lesson is if your Lightweight Norton has a really difficult and notchy gear change and it occasionally jumps out of gear check the ''Cam Drum Plunger Spring. You may find that you can solve your gear change problems by using a less strong spring or by using more than one sealing washer to reduce its strength......and at the same time cure an oil leak!
Apologies for the long explanation but I hope it may help others with similar gear change problems. I'm off to search the internet to find a box of Imperial sized copper washers.......wish me luck!
Safe riding. Cheers. Nick
Very useful stuff Nick...
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You are spot on Ian, all my…
You are spot on Ian, all my previous Lightweights had really slick and pleasant gear changes which is why I have spent so long chasing the problem on the Electra. I had checked the index plunger was moving freely when I rebuilt the transmission earlier in the year because they have been known to be 'sticky' and cause problems. I haven't found any information on the length of the spring but noted the one in my gearbox was quite strong. I note that the NOC spares list a replacement spring. I will buy one and compare it to mine when I next change the gearbox oil and report back. It is definitely an important factor in how smoothly the gearbox selects gears and as you say doesn't need to be particularly strong because once selected the dog should hold the selected gear.
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Well done
Nick,
That is a really good bit of work.
I too tried to improve the gear action on an Electra.
At some time in the past mine had obviously been left standing for years with old gearbox oil and a lot of moisture. Corrosion and some pitting on the plunger, which of course is at the lowest (most damp) part of the box.
A new plunger, polished on the chisel faces, and a polish of the plunger housing bore, made for a great improvement.
I believe I have the correct spring, but it does seem very strong.
If I can find a spare spring, might try chopping a couple of coils off to try for gear change Nirvana.
Peter
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That's very reassuring…
That's very reassuring feedback Peter which confirms my findings. Like you I was surprised at how strong my spring is and equally surprised with the improvement that three 1mm thick copper washers have made by reducing the load on the indexing plunger. If Norton didn't include a sealing washer on the screw in housing they must have used a much lighter spring than the one in mine otherwise gear selection would have been even worse......and so would the oil leaks! A very typical Lightweight Norton challenge but a step forward in finding your gear change Nirvana!!!
Enjoy riding the Electric in the summer weather while it lasts!
Nick
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... For various domestic reasons I haven't been able to get my Electra out on the road yet. However, I do remember that its gearchange was very good when I last rode it. Interestingly when running on the centre stand and selecting first from neutral, it snicks in very nicely with none of the clash of dogs I expected. This was without freeing the clutch plates first.
There shouldn't really be much force on the plunger once in gear as the gears are held in position by the gear dogs as long as these are in good condition.