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[jawa-enfield]

It was gear drive to the "distributor" last time I looked, not chain!

The cumulative build up of clearance between the 6 pinions involved can add up to about 10° of slop or backlash by the time you get to the final one for the ignition. You can compensate for this up to a point when timing on the full advance figure by winding on the "distributor" pinion anti-clockwise to take up the slack before setting finally tightening it in position.

I believe stinkwheel has opted for an Electrex World crankshaft-mounted CDI ignition or similar. My enthusiasm for these is somewhat reduced by the rather poor lighting output these kits provide.

https://www.electrexworld.co.uk/acatalog/STK-100D.html

A.

It was a fault in translation on my side.. A series of sprocket driving something is in Dutch a 'drive chain'

I thought matchless has it driven by a chain.. will be more accurate..

[Adrian]

Norton OHV singles too (at least those which haven't had weird side points conversions fitted). The magneto/distributor drive on the old Royal Enfield twin cylinder bikes IS by chain, however.

English references things like " a chain of islands", but for a row of timing gears I think we'd talk about a gear train.

A.

[stinkwheel]

Ahh, the wonders of the English language.

A toothed wheel driving another toothed wheel is a pinion or a cog, one driving a chain is a sprocket... Except on a fixed gear bicycle when it is also a cog, but only the one on the wheel, the front ones are chain-rings. It's only a gear if it's used to alter the speed of a driven output so I don't think the drive for the distributor is technically a gear because it rotates at 1x engine speed...

Then we could get into the whole sticky dilemma of axles, spindles and shafts...

[Duke of Wybourne.]

Norton OHV singles too (at least those which haven't had weird side points conversions fitted).

A.

That Norton revs in excess of 9000 rpm. It's got a weird head as well.

https://m.youtube.com/watch?v=RmcM0plhnRM

[Adrian]

That's not one of Pushrod Performance's specials, is it?

A.

[Duke of Wybourne.]

That's not one of Pushrod Performance's specials, is it?

A.

Home built Desmo.

[Wheaters]

My 350 iron barrel has TCI ignition, like the later UCE bikes. It all sits in the primary chain case and works really well. The AC headlight works really well, too. The charging rate seems to be very adequate because the ammeter needle only really fluctuates with the indicators on together with the brake light.

The only down side is that the timing cannot be readily adjusted; there’s no provision for it. Having said that, the bike runs really well.

[jawa-enfield]

It doesn't matter about the spark plug hole angle, when the plunger of the TDC tool is 8.5 mm on its own scale, before TDC, that will do. No need to over think things!

?? But.. Phytagoras and stuff? Won't it be around 6mm in reality?

No one defending my theory or.. is the timing so inaccurate by the play of the cogs/sprockets/chain/train-thingy that is doe not matter so much and i'm being too precise/insecure/autistic/perfectionalistic?

[windmill john]

I’m not normally so cavalier, but I’ve just advanced my Boyer backplate by a mill or so. Still no pinking, so am happy.
I did strobe it when the primary case was off, but didn’t remove for this tweak.

[stinkwheel]

No one defending my theory or.. is the timing so inaccurate by the play of the cogs/sprockets/chain/train-thingy that is doe not matter so much and i'm being too precise/insecure/autistic/perfectionalistic?

Pretty much. It'll give you a starting point at best.

If you want to set the timing properly, you'd want a degree wheel and pointer on the end of the crank, then check it with a strobe.

In real life, you set it in the usual manner then tweak it slightly from there until it appears to run best.

Indian Bullet-Wallahs set the static timing then with the points back plate not full tightened, then they start the engine and tap the points round in either direction by tapping the condenser with a screwdriver handle until they achieve the most consistant idle then fully tighten the screws.