Norton will notrun

<sigh>

The big day finally arrived. I've been rebuilding my 850 Commando for 2 months and today I got to kick it over. All I get is an occaisional POP out the exhaust.

New cam, timing chain and bearings. Rebuilt head. It's never been apart this far before. I took my time and I think I've done it all correctly. The engine is lubed with assembly lube and it's TIGHT. What a mother to kick.

OK, so I go through the checklist over and over again... Boyer is statically timed. Pickup leads are fresh and in the right spot. I get spark. Battery is charged.

Carbs are set the same way they were when I took it all apart. Fuel flows (tickler floods OK).

Timing chain was set per the workshop manual.. ten rollers between timing marks (six plates, per Chilton's). Unless the cam I got from Norvil has the key slot in the wrong place, it should be dead on.

Valve clearances are set (double checked) at 6 and 8. I've watched the valves open and close while feeling for piston movement and it seems OK. Of course I can't tell if it's one tooth off on the timing chain, but it's definitely not off 180.

Where would you guys start?

drc

Something simple? Battery good (enough for Boyer)? Fresh gas including in the float bowls and lines?

Take the sparkplugs out and kick it over. It should kick quite freely. If not, you definitely will need to disassemble. If it kicks through you have a valve timing issue. It always pays to degree in a new cam. Never know where that keyway may be.

You haven't set the Boyer ignition timing to the wrong alternator rotor mark by any chance, so that it's sparking 180 degrees out, (BBDC instead of BTDC)?

L.A.B. said:

You haven't set the Boyer ignition timing to the wrong alternator rotor mark by any chance, so that it's sparking 180 degrees out, (BBDC instead of BTDC)?

Click to expand...

Sounds like LAB is on the mark here. With the plugs out, see if the timing notch coincides with the pistons being at the top of the cylinders.

Another easy mistake is to time the Boyer rotor magnet to the wrong static timing hole in the pickup plate, as there are two holes, the lowest one is for clockwise rotation, and the upper hole is for anti-clockwise Norton (20M3S-on) Commando rotation.

Also make sure the wires haven't been crossed over somewhere between the Boyer box and the pickup?

Does it matter which of the two timing lines on the rotor are used to set the static timing? I figured that since it's wasted spark on one cylinder it didn't matter. I used the "upper" hole in the Boyer pickup plate per instructions. And yes, it kicks over easily without spark plugs in place.

Thanks guys. You're gonna love the pics of this beauty when I post the rebuild blog.

Just to reinforce what L.A.B. has said the two wires from the pickup MUST be connected the correct way to the control unit, the pickup is not just a simple trigger causing a spark.

maylar said:

Does it matter which of the two timing lines on the rotor are used to set the static timing? I figured that since it's wasted spark on one cylinder it didn't matter.

Click to expand...

Yes, it does matter, as it's a wasted spark system both plugs spark together each time, but only every 360 degrees of crankshaft rotation (= 180 degrees Boyer rotor rotation). As it is a 4 stroke engine with a 360 degree crank, if the wrong rotor mark is used to set the Boyer, then the sparks will occur 180 crank degrees out each time (pistons approaching Bottom DC).

To check you are using the right rotor mark, turn the crankshaft in its normal direction of rotation to approximately TDC, then turn the crank in the opposite direction. The first alternator rotor mark that lines up with the fixed timing mark (31 deg. BTDC for Boyer) will be the correct one to use, one Boyer magnet should then be in line with the pickup upper timing hole?
If the wrong alternator mark has been used, then the Boyer rotor magnets will be 90 degrees (= 180 crank degrees) off the hole.

L.A.B. said:

You haven't set the Boyer ignition timing to the wrong alternator rotor mark by any chance, so that it's sparking 180 degrees out, (BBDC instead of BTDC)?

Click to expand...

Yupper, that was it. Thanks all... she RUNS!