Amateur Manx 40M preparation

When inserting gearbox with righthand engine plate in place, it hits frame about 3/8 before it meets the engine plate.

Mike 40M said:

When inserting gearbox with righthand engine plate in place, it hits frame about 3/8 before it meets the engine plate.
View attachment 57329
View attachment 57337

Click to expand...

OK got it. how much do you need to remove for clearance?

If its not much say an 1/8 maybe 3/16 then option ;-

1 / Heat the frame in the troubled area till red , put a 1 inch bar across the and give it a clout (can't believe I am advising this).

Or

2 / Angle grind and clean off excess from the gearbox.

or

3 / A little of both (this is most likely what you will need to do.

Same issue on a Petty frame!

Mixing new and old often bring problems.

Gearbox will take some time. To make the workshop tidier, I will put some other things in place. Continued with forks (thanks jalsteve). For readers not familiar with fork assembly I'll show the special tools I've made. To compress fork just an ordinary luggage tie down. A rod with a long nut in one end that can be attached to the damper rod. When damper rod is up, I use a piece of metal with a milled slot. When rod is up, I slide it under the lock nut. Then it's just to replace the rod lifting tool with the fork top nut (and washer).

To make something easy for a change turned and fitted alloy barends. Then tried out flyscreen fittings. Have to figure out best top attachment. Will probably be tyraps and a piece of rubber. Booked same racenumber as it had last time. Saves me trouble of putting on a new number. Sent result of med test to federation, paid for licence.
Then continued with slimming gearbox. After a bit of milling found that counterboring 4mm for the offending Allen screw was needed. Tried it in place once again. Close but not enough. Turned a taper on the Allen head and did a little more alloy filing. Result is .031 clearance to frame.

Hoping that jalsteve will have time to spread his wisdom on rear hub parts, I contnued with gearbox installation. Spent yesterday evening filing LH engine plate to accomodate that fat and heavy TTI-box.
Now the gearbox and LH engine plate is in place. Shortened the bottom gearbox stud 4mm, so now it's possible to take gearbox in and out without raising and/or lowering engine. Norton should have done that mod themselves. As a final touch I drilled a 2mm hole in the gearbox and a washer with a tab also drilled 2 mm. So now I can lockwire engine and gearbox drain plugs.
Only tricky part in gearbox assembly is the top rear engine bolt. To get washer and nut in place below the magneto and behind magneto chain covers is a bit problematic.
Washer was put in place with help of a small magnet. For the nut a thin plastic glove with nut inside (on left hand thumb) worked surpricingly well. Blurry on picture.

Mike 40M said:

Hoping that jalsteve will have time to spread his wisdom on rear hub parts, I contnued with gearbox installation. Spent yesterday evening filing LH engine plate to accomodate that fat and heavy TTI-box.
Now the gearbox and LH engine plate is in place. Shortened the bottom gearbox stud 4mm, so now it's possible to take gearbox in and out without raising and/or lowering engine. Norton should have done that mod themselves. As a final touch I drilled a 2mm hole in the gearbox and a washer with a tab also drilled 2 mm. So now I can lockwire engine and gearbox drain plugs.
Only tricky part in gearbox assembly is the top rear engine bolt. To get washer and nut in place below the magneto and behind magneto chain covers is a bit problematic.
Washer was put in place with help of a small magnet. For the nut a thin plastic glove with nut inside (on left hand thumb) worked surpricingly well. Blurry on picture.
View attachment 57705

Click to expand...

Springs - There are 3 on the rear brake plate. The shoes have two as normal, one at the cam and one at the pivot. The third is fitted behind the brake operating arm BUT often this one is left off. The brake shoe springs are heavy gauge and not like those you would find on a road bike. Andy Molnar can supply, its probably best to replace anyway.

Have a really close look around all the spoke holes for cracks and ESPECIALLY inside the hub were the large cast spokes meet the outer casting as they are prone to crack. If you find a crack the hub is scrap, don't be tempted to weld, and don't be temped to use.

The problematic top engine bolt - just get a piece of bar (you can use Dural) say 50mm x 20mm x 12.5 (1/2 thick), drill a hole at one end and tap 3/8" 26tpi replace the nut with this. the length allows you to easily fit and its hidden so doesn't affect the way the bike looks. This was a period mod.

Some photos of a a Manx rear brake plate. Replica but exactly as original.

Looking at the out side of the brake plate you will note a small peg on the plate near the brake arm this is the anchor for an external brake arm spring. And on the photo of the inside note the heavy brake shoe springs.

The clutch roller bearings are a point of weakness. There are 15 1/4x1/4 rollers held in a pressed steel cage, a period mod was to replace with 50 1/4x1/4 rollers which gives better support to the chain wheel (basket) and helps it run more true with less movement. Lubricate with a HM lithium non fluid grease, you don't need lots as you will be removing the plates and giving them a clean after every race and can add a little grease at that time?

Which clutch are you using? The Burman type with inserts in the chain wheel or AMC with a friction back plate? They are both good clutches if its original Manx clutch (centre with have 6 bolts) please don't use for racing they are rare today and you will destroy it. Buy and modified a road AMC clutch just narrow it down for 4 plates. Or you can be similar from Andover Norton. Run the primary with about 25mm of up and down movement (that's an easy inch!!!). As the engine warn up it heats the gearbox and engine plates so centre of clutch to crank centre increases. I always run the bike around at low rpm and get all nice an hot then stop and check the tension of the primary chain, when hot there must be a little play. I have seen gearbox main shafts snap in race conditions and drive side main bearing wrecked through over tight chains. Belts are more forgiving.

Ref bearing seals - Correct there are no seals as the wheel spacers or brake plates collars act as deflectors. Just pack with a good quality LM grease.

Sad to say, have been busy with other things. Not much done to the Manx. My neighbour calls it the mailorder bike. Just because all delivery vans and lorries that come with small and big parcels.
Next week nothing will be done to it. Then I'll do the rear wheel, get primary drive in line and try to fix a leak in left fork leg.
The original (?) clutch is a mysterious thing to me.

Notice the spring screws with 1/4" square holes. Basket and pressure plate lightened. No steel cage but filled with a lot of rollers. 6 Allen screws. Friction plates and centre different size of "splines" than other Nortons. Steel plates probably usual size. Sadly it had a hard life, centre much worn. Will use an Andover clutch.
Some small things done. Replaced rubber mount for float bowl and made a gear lever.

Clutch springs round section, think original did not last for 9 years of hard racing. Friend borrowed an excavator from me, in return took new clutch parts to machine them as old one. Nice to have friends with CNC-machines, when you only have manual machines. Race scrutineers nowadays might have some opinions on some original parts, so some parts had to be made. Alloy footrests done and threaded 7/16 BSC. Since the old Arrgardh gearbox had a reverse gearlever, a temporary gearlever is made. If the bike is ever is running again, I'll decide what length it shall have and make a period looking one. The TTI-box was ordered with that in mind, so it will be the usual 1st up, the rest down as all my other English bikes have. Today made a .6mm shim under engine sprocket. Primary chain is now quite inline.
As nearest Manx I know of is some 150 miles away, there are things that I can't figure out.
What does bolt or stud holding front of chainguard look like?
Since most of the oil and breather lines was a real mess when I got the bike, advice please. That upper line to oil tank is return and lower is supply is probably right but the rest?
Have to make a tool for retainer holding rear wheel bearing. Difficult to figure out diameter for the 4 holes. Of course a hammerhappy cretin had been there.

I hate lockwiring. Not the wiring but drilling the holes. Bolts is easy compared to nuts. Worst is nuts in oil fittings. Finally bought some tiny endmills which made it a lot easier. Starting with an endmill and then changed to a drill. Now the drill breaks when going out instead of when starting. Managed to make 5 holes whith only one broken drill. New record
Not much room to lockwire oil lines on a Manx. Luckily had some forceps which made it easy.

Yes the temporary gearlever is hideous.

What to do if the thread is knackered, new 3/8 thread cut into the old hole (was 5/16). Narrow a bolt head with the correct thread and drill centre to 1/4bsf stud needs to be long enough to be able to move the position of the guard to be centre over the chain.

As original with stepped stud 5/16 and 1/4 threads. Belt drive primary but it's the same mounting type.