change my pre monbloc as it had a 1/16 play in the slide bit worn 70 years old so put a new monobloc carb on my bike now i run three types of carbs on all of my bike.Observation - Banging in the exhaust when trying to start suggest the ignition timing is possibly way out.
First Principles to be attended to in order for a Comet:
1. Valve Timing - set the camshaft position so you have EQUAL lift of the exhaust and inlet valves between 5 BTDC and 3 BTDC. 4 BTDC is ideal. Ignore marks on the timing gears - use a degree wheel and measure everything
2. If you are using the timed breather, it should close between 5 ABDC and 10 ABDC
3. Valve clearance is zero when stone cold BUT you must be able to rotate the pushrods
4. Magneto points between 0.012" and 0.015"
5. Spark Plug gap 0.018" with a Lucas magneto
6. Ignition Timing for easy first kick starting 4 BTDC fully retarded and for reliable running without the risk of modern crap fuel killing the motor no more than 34 BTDC fully advanced.
6. Carb adjustments - see attached guide and note that the pilot jet needle should be approx 1 1/4 turns out from fully closed.
7. If the carb is worn (most likely) have it professional rebuilt or replace it.
If you need more info on how to do any of these things - just ask.
The hole visible just above top of the base cap of an assembled carburetor is the one through which I've inserted a drill bit in the jet block of a Shadow carburetor in the first photograph.From MPH 737 "The correct 276 float level is just below the hole that exits at the top of the base cap so that fuel does not flow out of it continually"
What's your contact info?Everiman, I am located in Ottawa and am intimately familiar with the Lucas K-series mags. Full disclosure: I restore Lucas mags and dynamos as my business.
Why not ship your mag over and I'll inspect it for you?
.. Gregg
Surely it would be easier to replace the cam ring with a single one, making sure which pickup is still firing before blanking the other off, one of the firing positions must still line up as you cannot change the flux positions on the armature.The cheap and dirty way to do it would be to replace the mag's twin cylinder slip ring with a single cylinder slip ring, and plug the hole for the second HT pickup. That way the second spark would fire the same plug on the exhaust stroke, just like a "wasted spark" configuration on a twin.
.. Gregg