Improvements to the lightweights

I totally agree with all that you have done John, 12v conversion using a modern Lucas stator and voltage reg/rect, Pazon electric ignition and a rebuilt carb completely transformed my late Navigator!   It has the later clutch and gearbox which I have always felt are better than the earlier type although the ratios are the same I believe.   I have fitted Norton straight bars and good quality, ball ended levers plus rebuilt wheels and brakes which have all added up to a really enjoyable, surprisingly nippy bike with fantastic handling and brakes for it's era.   I cured the oil leaks by replacing the primary side crankshaft, clutch and gear box oil seals, the timing side points oil seal and replaced the sump plate with the modified and finned sump plate with the magnetic drain plug sold by the NOC shop.   Using two of the rediculously thin rocker box gaskets on each rocker box and silicone sealant on the primary chain case has cured all the oil leaks and it seems happiest running on a straight 40 grade classic oil but each to their own!   Mine has done 32,000 miles on the clock but I have no idea whether it is on standard pistons although the compression is good and there is little or no blow by - a sure sign that the top end is in good condition and the design of the crankcase breathing is adequate if the engine is in good order.   As for other improvements there is very little history of anyone 'tuning' any of the Lightweights.   If you search through the various threads on this forum there is evidence of a racing Jubilee which was tuned successfully with much stronger valve springs to let it rev to frightening levels and supposedly similar power output to a Navigator.  Evidently valve bounce (and probably piston fragility!!!) because of weak original springs limits performance hence use of stronger springs.   Valve angle is another limiting factor along with the inlet ports being so close together and to little space between the head and main frame to fit twin carbs.   The cam followers are prone to wear rapidly which makes the engine noisy and I have read opinion that the valve train is heavy which again limits it's ability to rev but I'm not so sure about that!   Our wonderful technical expert, Andy Sochanik can tell you more.   As and when I need to do an engine rebuild I will explore gas flowing the heads and carefully balancing and blue printing the engine then once it is run in using a slightly bigger carb, say from the Electra - every little helps!   I would welcome hearing how you develop yours, after three years of Navigator ownership I am a huge fan of what is a far better bike than some (who have probably never owned or ridden one) would tell you!   Mine is a 'keeper'!   Good luck and keep us updated.   Cheers Nick             

My atlas valves looked a bit pocketed, but rather than getting new seats  I got my local old bike engineer to blend in the chamber side  with his cutters . As long as the rocker action is still centered on the valve tips its a reasonable compromise..Might be good to check the spring poundage with it being a higher revving motor.

Hi John,

I like Nicholas Clarke's reply. His are all good suggestions.

Improvements are very personal and depend on the use you make of the bike. These were mine.

Get the bike oil tight. Keep on top of maintenance.

Riding mirror.

Improved centre stand bushes.

Strengthen centre stand shaft between legs.

Get a centre stand with extended leg for foot. (Electra style)

Fit a decent side stand. 

Stainless rims, spokes, handlebars and fasteners wherever I can.

Control levers for brake and clutch with adjusters that you can adjust on the go. (Need special cables)

LED's for power, indicator, Lo/Hi beam.

Handlebar clock.

Strong luggage rack in Craven style.

Pannier frame.

Map holder.

Handlebar mounted device that has three numbered rings (from a number padlock) that can record the list three digits of the odometer when the fuel tank is filled.

And I think you can see what I like about my Norton Lightweight. It's personal isn't it!

All the best with yours. Endless possibilities.

Peter

Hi All,

This thread has made fascinating reading. I love John's ideas of steady improvement (plus Nicholas's thoughts) - not necessarily for speed, but to make the breed better. It was inevitably built down to a price in the day, and with hindsight we can improve on stuff.

In my case, I'm happy on 6v and points. My headlight bulb (from Paul Goff) is a normal filament one, and is focussed just right - so I have no problems at night. If you are staying with 6v, do NOT be tempted to use LED lights!! The original 6v electrical system is balanced (did you notice the resistance wire in the loom?) so as not to overcharge the battery. LED bulbs (esp the headlight) consume less power, thus leaving a greater excess to boil your battery.

But never mind what I do - these days it makes much more sense to upgrade to 12v. Your original Wipac stator (if in good condition) is up to it - just connect the Orange & Green wires together & you have a 2-wire output system. As stated above, a modern Lucas Stator is fine with the strong (Wipac rotor) if replacement is needed. You will need to do some wiring mods - contact me or Al Osborn for details. Once on 12v, the best thing is, that you can add a regulator/rectifier (to replace the original rectifier) & remove the resistance wire from the equation -  plus electronic ignition. Most electronic systems fire both coils in series (wasted spark system) thus you get to keep your existing 6v coils. Alas, Electra owners converting to Electronic Ignition will need to source 2x 6v coils!

An important mod for me was to fit a rear carrier, and then add strength to it by triangulation. Failure to do so wrecks your rear mudguard (as I found to my cost), as the stain imposed by the carrier distorts the mudguard. See picture attached. Its not pretty, but is super strong.

For John, I need to ask your engine number. You may have deduced from the replies above that there are two differing gearboxes used. There is a break point at engine No 106838 (mine is 106840!!). All Electra, plus Jubilees & Navigators after that number, have a re-designed gearbox, and NO parts from it are compatible to the earlier version. Even the frames & crankcase castings are different, leading to different shape centre stand springs & 'C' shape anchors.

Both gearboxes have their good & bad points:

The 'early' gearbox provides a really smooth AMC-type gearchange - and has a kickstart system that never wears out, but has a bad issue with the layshaft bush adjacent to the sleeve gear bearing. It was not pegged in place at the factory, thus has a habit of rotating in its housing (the crankcase) and can create havoc. If the bike is new to you, its worth tearing down your gearbox, to ensure all is OK in that department. (Like a timing belt on a car - if you don't know its history, its worth replacing for peace of mind).

The 'later' gearbox is potentially stronger, as it has a larger diameter mainshaft, and the layshaft bush is pegged to avoid rotation. But, it is clunky in operation & has a piddly kickstart pawl which can fail suddenly, with no warning.

Another thing to look at are the clamping bolts for the rocker shafts. The first Jubilees and Navigators had 1/8" diameter bolts clamping the rockers after adjustment. These can bend and release the rocker shaft - which immediately goes to maximum adjustment & that cylinder cuts out. Its happened once to me when I had an older cylinder head fitted. I was lucky as the pushrod stayed put, but I have seen damaged pushrods (at autojumbles), so others have not been so lucky. Later cylinders heads have 3/16" bolts that are much stronger.

There are two sources of oil leak on the cylinder head, noticeable by oil running down the front of the engine (as its inclined forwards). One is the rocker caps themselves - as only 2 bolts hold them them down. If leaking, the temptation is to tighten the bolts - whereupon the leak gets worse! One person has written above about using two gaskets & silicon (which should work), but my preffered route is a cork impregnated gasket of about 1/16" (1mm?) - similar type to that used on car rocker boxed, but thinner. This works a treat, as it gets compressed by the screws, and is thick enough to absorb any distortion. The other source is the rocker oil feed pipe. The unions are soldered on, and 9 times out of ten, if I have an oil leak upstairs - its because the soldering has let go. To check, remove the pipe from the top of the engine, hold the unions between thumb and forefinger & twist them back & forth against each other.

On pre-106838 engines, the crankcase breather needs re-siting. Sadly, its a job for when the crankcases are apart for a major overhaul. Its present location behind the Primary inner case and above the output gearbox sprocket is not only bad (as the chain can cut into the pipe on the over-run), but one is unable to do anything about it with dismantling the whole primary drive. Engines after 106838 have the breather exiting at the rear of the crankcase - eliminating that potential source of oil leak.

Another idea that has been floating about recently, is employing a reed valve in the engine breather circuit, thus creating a potentially negative pressure under the pistons, thus not 'pushing' oil out of any available orifice. I have not tried it yet - but have heard from 2 people who say its made a vast inprovement.

Also touched on above, is the need to add an oil filter kit and a tap to stop oil draining past past the oil pump and ending up in the sump. Any tap fitted must be full-flow (you can see through it when open) and MUST have an ignition cut-out fitted - otherwise you WILL ride off one day with the tap closed. The oil Filter fits in the return line, so is not ideal - but better than nothing.

Picture of my Navi showing triangulation to the rear carrier and the same bike 30yrs ago without the supports. Next to it is a DeLux JOO 804 which I then sold to a chap for a pittance soon after (£250??). He did not haggle & just chucked it in his van. I felt like I'd been robbed. Sure enough - I had been!! Have a look on the DVLA site for that Number Plate now......(by checking 'Is my Tax due'...)