Not so rich but now backfiring

I'm having a hell of a time getting my rebuilt 71 750 to run smoothly. I've heard how Nortons are supposed to sound (glorious) but this old girls runs like crap.
Story so far:

New Boyer and spark looks good.
New 106 needle and jets: plugs appropriately coloured (this after considerable fettling).
Compression ~ 150 both sides.

but;

difficult to start - often requires ether
backfire on right side
General rough engine as I throttle up and it gets worse under load.
oil smoke (I know; guides)

I've almost had it with this bike and the 68 Triumph is looking better every day (it keeps going and going ...).

Any suggestions/help would be greatly appreciated.

BC

Dual carbs or single? What carb(s)?

Air leak in exhaust on backfire side?

Answer: Loose ground wire on the Boyer. I love my Norton.

(Dual original Amals, BTW)

BC

Ole Brit Iron Motto - if it feels sounds and smells like fuel problem check electrics first. The over rich or over lean states I've found in my or a friends Cdo did not cause backfiring, only poor starts, poor idle usually too fast or *mis firing* from leaving choke on or some carb system air leaks. Make sure boyah is getting its full voltage from good alternator and all current connections and for sure order trigger wire upgrades or DIY or except to be inspection back fires, mis fires and silence away from home. A look after dark key on [out of gear] probe, tug, jerking loom can cause a pop or a flash to alert to electrical source and can't forget ya can have more than one issue both causing same symptoms at once. Kill switch could do this as can key fob bouncing in worn switch. Keep water in fuel in back of mind too.

If you have experience with setting up dual Amals, then I think the problem is timing. You say re-built motor? Has the cam timing been verified? One chain pin out and its going to run like crap. Boyer timing has to be set static 30 degrees before TDC and then strobe timed. The Boyer must have a healthy battery 12V otherwise it breaks down. Make sure all ignition wires, earths and coil leads are firm.

Stillreel said:

Answer: Loose ground wire on the Boyer. I love my Norton.

(Dual original Amals, BTW)

BC

Click to expand...

So, all is well, running like a dream, Sounds glorious, no more issue?

I must of been typing when the answer showed up but do remember that sense for the future.

pete.v said:

So, all is well, running like a dream, Sounds glorious, no more issue?

Click to expand...

Still a lot of white smoke art start up but I'm thinking this is a leaky exhausrt value guide and that can wait for the winter rebuild project.

It really does sound awesome. I could mess with the timing a bit to get that lngering rumble coming off the throttle but right now (knock on wood ~ many times ~ hard) it's running well. We'll see how long that lasts.

If any of you out there see a yellow Norton and an exasperated rider at the side of the road in the Toronto area. It will be me.

BC

Guide leaks get worse riding while rings start up smoking but clear a lot as warmed up. Rings tend to more smoke on rev ups while guides more on let offs. Could be both at once and something else leaking too.

Stillreel said:

Still a lot of white smoke art start up but I'm thinking this is a leaky exhausrt value guide and that can wait for the winter rebuild project.

Click to expand...

Both cylinders? Bad/cheap gas? Watered down?

One cylinder? Guide or head gasket going away? No, that's if your are water cooled. Torque your head anyhow.

If it was a leaky guide wouldn't you see exhaust smoke after gear changes due to the vacuum on over-run when the throttle closes ?

The white smoke issue is evident only from the left side exhaust and disappears after 5 minutes running. I rationalize it as a valve guide as oil seeping down the guide valve clearance after shut off. But then I may be mad.

No coolant issues that I can see, being air cooled but I will torque the head down again.

Thanks all,

BC