Nut size and type.

Hi John,

The nuts originally provided by AMC for engine mounting on a lightweight were:

Steel, zinc plated and passivated to light grey. (Pt no E3224)

A full nut with sharp corners on one side and radius (broken) corners on the other side.

Threaded 3/8 british cycle thread. 26tpi.

Made of a hexagon size conforming to the BSW/BSF range. Probably the regular 5/16 BSW hexagon size. (Cycle nuts are usually smaller hexagons than BSW nuts of the same thread size).

The exception is the rear right lower engine mounting nut on the early gearbox versions. This nut is a special form to acommodate the centre stand spring support arm. (Pt no 21166)

On later gearbox versions, both ends of the lower end stud are special form nuts to accomodate the slotted mount in the later centre frame section.(Pt no 24621)

There will probably be a lot of other replies telling different stories describing alternatives, but a parts book will tell you the part numbers. Luckily I've seen a few unmolested lightweights.

Hope this answers your question.

Peter

John,

All lightweights use the same seal behind the engine sprocket. T2187.

Previous owner who had difficulty removing the roller outer race from the crankcase of this engine drilled two holes through to punch the race out. A popular move I am told. Left to wet sump, or even in regular use, oil will migrate into the primary chaincase as you describe. 

Soon after introduction, Norton/AMC peened in 3 places after the new seal was fitted so that the seal would not push out under increased crankcase pressure. You get this increased crankcase pressure when starting a bike that has 'wet sumped' all or most of the oil tank contents into the crankcase. Let the engine tick over until oil is pumped back to the sump and normal service can resume.

The seal behind the clutch stops oil leaking out of the primary drive, so not contributing to oil in primary drive. This seal varies in size, and part number, according to the engine part number. Pre/post engine 106838.

You still need that parts list John.

Peter

Hi John, 

If yours has the two holes as Peters, I would tap them out and fit grub-screws with setting sealant to prevent crankcase pressure blowing oil through from crankcase pressure.If you are not stripping the engine use plenty of grease on the tap and remove and clean every couple of turns. Stop as soon as you touch the bearing, check the depth to the bearing before starting and make sure the grub screw is below the surface when tightened . They should tighten up into the taper produced by the tap.

Regards

Dick
 

I used JB weld ..... am I bad?! ..... it’s held so far.

dan

.. you can thoroughly degrease the area nothing wrong with JB weld for this job as it's not under any great stress.