I can't start my Commando!

not quite sure what you mean regarding the timing marks? also it is well known that boyer ignitions suffer from the pickup wires fracturing at the pickup connection on the printed circuit it may spark ok when you have moved it?,have you got a full 12 volts at the ignition? how old is the fuel? if it has gone off it can produce the symptoms also make sure the carb is clean pilot jet not blocked etc, go back over what you have checked good luck with it regards nick

Oh dear Keith, you moved the timing! Never mind, as you say, the two 90 degree positions should give the same outcome. A Commando will start +/- 20 degrees from the correct timing anyway.

I would agree with Nicholas and suggest it is manky petrol and a blocked up pair of carburettors. Squirt about 2ml of fresh neat petrol down the carb inlets and give a kick with a 1/4 throttle. If you get a brief roar then it is the old fuel, and possibly blockages.

Check that your battery has enough power for the Boyer - is the headlamp bright?

Best wishes!

A couple of things spring to mind.

There have been camshafts with insufficiently deep thread and Boyer supplied too long a screw at one time. Both of these result in the screw bottoming out with the rotor perhaps still able to move and vary the timing.

The most likely cause in my opinion is battery condition. The Boyer needs battery volts to regulate the amount of retardation. If only a couple of volts low, it will default to full advance and kick back and spit. It will of course still show a spark but not at the right moment.

It's certainly worth giving the battery a good charge and checking condition. If in doubt, replace. Boyers just can't cope with an example that is less than 100% and it is one of the disadvantages of the system.

Your feedback is helpful as you are confirming that a) the battery is good and headlamp bright, b) the fuel is recent and the carburettor now cleaned.

So we are now faced with the question "what could have changed while the bike was sat in the garage"? This tends to rule out mechanical things like bolts coming undone or cylinder heads cracking. To confirm that valves are not sticking do you still have good compression when kicking over?

The most likely things are still the two items in the first paragraph: a) insufficient volts are reaching the Boyer, b) fuel is not getting into the cylinders. Either of these failures will cause spit backs due to being over advanced and/or weak.

An electrical connection can rapidly corrode in storage. Try and measure the voltage at the Boyer feed wire and compare that with the battery posts when all is switched on; there should be no more than 0.2 - 0.3 volts difference. Wiggle and WD40 all the connectors.

Have you tried a small shot of petrol down the Mikuni, sorry I did not spot you said you had one of these when I previously referred to a pair of carburettors. When I had a Mikuni fitted the bike would not start, and would spit back, if the choke was not fully on. Could the choke not be working?

Have more fun in the garage today! I'm off steaming little railway engines. Hopefully the rain will be late coming.

In an earlier thread I highlighted how my ignition timing was compromised by me being smart and trying to make a better set of connections on my Boyer back plate. Basically I routed a couple of insulated solid copper wires across the front of the board to a screw type connector, This gave me ignition timing that made the bike unrideable and impossible to fettle. I wasted hours, no days, trying to time it and get it to run properly. Working on the theory that "it was probably the last thing you were fiddling with" I returned the pickup layout to near normal and bingo problem solved.

Try re-routing the wires from your boyer pick up, even outside the cases temporarily to see if that has any effect.

Given that your battery is good and that your fuel not stale. (Ideally with no ethanol) If we also assume that your bike has not partially wet sumped, slowing the engine turning over for kick startingand we know your carb is cleanthen there is only one thing for it, given that the Boyer will work well off the correct timing and fire the engine.(Plugs Champion NY7C) Use a single Amal, 32mm on the 850.Use the correct spray tube, 4 ring needle, 3 1/2 cutaway and a 260 main jet. Sorted! Keep biking British.......Especially Norton's.

Twin carbs on a Commando please. Premier Amals are reported to work very well, so no need to strangle the performance with a single carb.

Keith........on my Boyer powered Norton Commando, the engine would fire but not run. The cause was that, by mistake,I had set up the pick-up plate for a Dommie. So that the ignition was retarding after firing. The Dommie rotor turns clockwise whereas the Commando is anti-clockwise.

Later on, with the same set-up, I discovered that if the battery dropped below 12 volts, the engine would just keep backfiring but not run.

Finally, don't Commando bikes have a dodgy bit of equipment called a Ballast Resistor which can mess up any plans for riding the bike???

Nowt wrong with a single carb. Do we ever ride with the throttles hard against the stop to get that last mph? Not legally we don't. I even raced my Domi on a single carb to a podium place in the Scottish Championship. So performance wasn't too strangled.

Could you by any chance have reversed the wires from the ignition pick up to the Boyer unit ? Whilst it doesn't matter in terms of providing a spark as both fire together, it does prevent the advance-retard working as it should.

I've never had a static set-up too far out on a Boyer for it not to start without problems.

Remove the plugs, bring it up to tdc, put it in gear and gently jerk the rear wheel backwards until the stator mark lines up with the indicator (which may be a bit out, but not too far).

Line up the rotor horizontally. This is a rough guide. Ideally, a screw on the rotor should be visible through the hole in the stator when the plate is in the middle of the slots.

If you follow this procedure then the timing will be accurate enough to start and run without the symptoms that you're describing.

If, despite this, it's still kicking back and trying to bruise your feet, then I'd say that it is not retarding which probably means either low battery volts or a wrong connection.

Even new batteries can give trouble. Can you try it connected to a car battery ?

There were a few showers Keith, but in Northampton the Sunday weather was nothing like as bad as the forecast was claiming.

You are getting closer since your added petrol test indicated that it is probably the sparks and not the carburettor.

As Richard says, carefully re-check the static timing, especially as you have disturbed it. The strobe wil be no use until it is running steadily. The timing can be + or - 20 deg and it should start, sort of; but a static set-up is usually within 5 deg and sometimes bang on. I once put my Boyer rotor on in a hurry, started it, and looking at the strobe found it was reading around 30 deg at 1,500 RPM and went clean off the scale heading past 50 deg as the revs picked up. I quickly shouted to my son to stop applying throttle and kill the ignition.

I would still look for a bad electrical connection next. Run a direct piece of wire from the battery to feed the Boyer amplifier, and double check the amplifier earth. Will it start now? The healthy, blue spark does not confirm that the Boyer is getting enough volts to time accurately.