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I so hate to need to make this thread.
I certainly don't know it all but I've been around long enough to know the basics and then some.
Engine has new standard size pistons and rings. Lapped the valves, head appeared in good shape.
Tappets at .008" and .010"
Using this style coil, same one in my running Triumph.

Spark looks good, big.
Points ignition. Timed with advance locked to 34 BTDC (tricky since I found out too late the flywheel was put on wrong so no timing slot available)
Swapped out Monoblocs (Did try them) for a pair of Concentrics since I'm more familiar with them. Pilot jet clear.
Cold (obviously) compression is 90 both sides. I know that is low but my Triumph is the same and runs fine. Maybe its the gauge-maybe not.
Tried new NGK plugs and new Champion N3.
Starter fluid or gas sprayed in carbs and still not even a pop.

Obviously doing something wrong. Deja vu for the Triumph which I struggled with for longer than I care to say.
Turned out I had a bad Boyer box. Put in points and Vroom!

Any ideas or direction most appreciated.

is it sparking on the induction stroke maybe?, check points are opening when both valves are closed for the respective cylinder.

Thanks Gavin, no, it's not that. Just now took off the rocker cover to look things over.

Float level is good by the way. Any higher it would flood.

Rags in the inlet tract? Ive done that before.

Electrical short, acting like a kill switch? How's the ZD?

How are you checking spark? Are you moving anything around other than the plug and wire? Are you checking both sides?

Do you see 12v at both coil poles? Good ground on the shared pole?

Are you using the same timing hole on the trigger plate as you are on your triumph? If so this will be the problem, regardless of you having the crank correct when you did it, the spark will be at the wrong point. you want to align the dot with the one that’s anti clock wise aka left hand side of the stator coil.

Otherwise check the Boyer rotor has good magnetism with a screwdriver or spanner (non magnetic) on both of the magnets. I had one which was bad from new. It sparked with the plugs out of the head but not when fitted. Don’t get why. Anyway LP Williams who I bought it off sent me another one straight away - great service!

I don't get this, how can the flywheel be mounted wrong, is it on back to front? If you cant use the flywheel timing slot how did you time the ignition, degree disc maybe?

From reading your post it sounds like you are using points in which case I believe the AAU has to be bolted into the fully advanced position with the crank also locked into the fully advanced position. Maybe a mismatch somewhere.

Might be worth checking the cam timing as well in case something is amiss.

this coil is wired to 2 sets of points ?
how is it wired ?

Never heard of this. Please explain.
Sorry, forgot to mention I'm using a Podtronics. Wiring is very simple at this point. No headlight/taillight yet.
Checking the spark on both plugs laying on the head.
Points ignition - not Boyer this time.
The center post on the coil is positive from battery and outer negative posts each to a point. (negative ground wiring)

This is facing front of engine. Timing slot on wrong side!
I measured the piston height with a dial gauge when engine was apart and marked rotor/stator at 34 degrees BTDC
Locked AAU advanced with washer on bolt.

Cam timing set by aligning marks on gears. I don't know much about varying these settings and reasons for it.
Valves seem to be opening and closing roughly when they should.

Thanks for all the replies!

Hi,
Are the condensers in good shape?
If the wires to the points were reversed then the timing would be on the wrong stroke
There was a old post on this type of coil that may help?
http://www.britbike.com/forums/ubbthreads.php/topics/768139/1

John

Not so long ago I had an "issue" after a rebuild when the bike would only run on one cylinder, on investigation I found a rag still blocking the inlet port, whoops!
Measuring piston height to guestimate firing angle is not as accurate as using a degree wheel zeroed at TDC using a fixed stop to calibrate. Still it should be close enough to make it run. Are you sure the correct points are firing the correct plugs when the correct cylinder is on comp.?

If you've got spark and fuel the way you've described, the only thing left is compression. A compression test won't tell you if you're firing with the valves wide open. An easy test could be to swap the neg wires at the coil.

You should be getting a pop or sputter or something.

When I first got my A50 I didn't realize the cam pinion rotates in the opposite direction of the crank so I had the points 34' after TDC. wouldn't start.

Well you have something very wrong
So if it were in my shed, the timing disc would come out ( if I could find it ) and get stuck to the rotor nut with a magnet because you are just checking things.
TDC located using a piston stop then a bull dog clip on a fin or a pair of long nose vise grips etc to hang a pointer off.
Then the engine would go through several rotations while I noted the valve opening & closing degrees, and points opening & closing degrees
When the numbers have been measured draw a strait line on some graph paper if you have it.
Make the X axis 7.2" long then every 1/10" = 10 degrees of crankshaft rotation.
Next plot each valve opening and closing plus points opening & closing for each cylinder as individual lines.
When finished you will have 6 partial horizontal lines Left inlet , left exhaust, left points and the same for the right.
Mark TDC & BDC vertically.
If the points or valves are out of time it will now jump up off the page & bite you on the nose.

IF not take a photo & post it here and those who have already made all of the silly mistakes before you will see a repetition of their Boo Boo & set your strait.
Just remember to add 360 deg for things thathappen onthe 2nd rotation.

Have you tried smaller gap on spark plugs? I just had a problem with my Atlas. Was doing service on 3 of my bikes and set all plugs to .025" and on the Atlas had a nice spark outside the engine but not even a pop when installed. This bike runs a mag and I checked everything and was almost ready to remove mag when I thought of plug gap. Bit of research found gap should be around.018". Adjusted gap and it fired and ran first kick. Not saying this is your problem, but know for sure it was mine.

Good luck, Bill

Still no go. Thanks for the replies.
I'm definitely firing my sparks on the correct cylinders.
Double, triple checking everything. Put on a degree wheel to confirm valve opening and closing points.
Not with any real accuracy though. Couldn't figure out how to put my dial gauge on.

Sprayed some carb cleaner through the air screw holes and the air entry holes on the back of the carb to see it spray
out the two little holes and confirm my primary idle circuit is clear and working.
Condensers? I'll try a smaller plug gap. Currently at .02"

You dont need a dial gauge, you do need to open the valve clearances up to 0.015", as soon as all the clearance is taken up ( judge with a cigarette paper between valve tip and adjuster), that is the opening point, you dont need all 4 reading, so long as the inlet or exhaust is opening within 5 degrees or so of the book number then you are good to go. The reason for the 15 thou clearance is because the cams have slow opening ramps to keep some of the clatter down.

Ah, Thank you! Never heard of that trick!

Some random thoughts which may or may not help:-
- is the carb balance pipe fitted?
- are the carbs at least loosly tuned, e.g. throttle cables slack, slides bottoming, pilot mixture 1-1/2 turns out and idle stops turned in slightly?
- any air leaks around the inlet manifolds?
- what do the plugs smell/look like after starting attempts? I would hope that you can at least smell petrol and they arent black/shiny
- is the fuel fresh?
- what about battery charge status, do you have at least 12v and a good earth connection especially to the engine?
- what type of points plate is fitted 4CA or 6CA and what about the AAU springs, is there any slack?
- have you double-checked the cam timing, sometimes there is more than one timing mark on the pinions.

I had a nightmare like this years ago after a rebuild. I found out that the smooth valve cover was stopping one of the valves from fully closing, due to the aftermarket tappet/replacement valves hitting the inside of the cover. Not immediately apparent, but after starting sans cover, a little work with a grinding wheel and all was well.

I'll be doing this more closely using Gavins method.
Also going to try advancing/retarding the spark at bit.
I tightened up my plug gap on the tight side of .02". Since then I'm at least getting a bit of a "whoom" on kick.

Sounds like progress, I'm sure the bike will be started soon.

If the plugs are not wet, look V closely at the pilot mix delivery holes in the floor of the carb venturi, theres one in front of the slide front lip and one behind it, make sure these are clear. If you spray whatever your go to WD 40 stuff is in through the carb inlet pilot air hole, the one on the bottom lip that isnt plugged you should see stuff coming through the two wee holes ( it will also spray into the float bowl, hold your finger over that hole).
You squished O ring doesnt sound right

Thanks. Checked carb. See post #811453.

That 15 thou thing, that not Gavins method, RTFM.