Are these 'symptoms' of a "black Box' Breakdown?

[s clarke]

Hi all, been away from this list for some years, now presently bringing my 'retirement' project back to life, '79 Xs11 Std, and at first fire up, ran strong, kicked down choke, ran sweet, then started to backfire through the #4 carb pod air filter, which progressed to puffs of black smoke, rough running, short flames out of the single muffler, then BANG, more smoke, repeat. Shut motor off, checked carbs, plugs, 'dressed' up end of wire for that plug, tried again. Before this point, #4 exhaust pipe was cold, rest hot, now, running ragged, thick black smoke out of muffler, # 1 and #2 exhaust pipes cold, #3 and # 4 hot. Will check wires under left side cover tomorrow for breaks, but fear that 'Black Box' is starting to go away. Any thoughts on this issue?
Cheers
SQUID

[Ken Talbot]

If pipes 1 and 2 are now cold, look for a problem with fuel supply as that is the common link between those two. Do you still have the 'octy' on that bike?

[s clarke]

No "octy"

Ken, no 'octy', just petcocks to carbs, return vacuum line to other tap on petcock. Will rebuild carbs tomorrow, and synch same.
Thanks
Syd

[SFerinTEXAS]

return vacuum line to other tap on petcock.

What vac line is that? Coming from where?

[James England]

At this stage, it could be anything and I would not jump to the conclusion that it's the black box. In general they are pretty reliable. How long has the bike been standing unused? On side stand or centre stand? How old is the fuel in it?

It looks like a fuel issue to me. Before stripping carbs, I would remove all the plugs and lay them on the head and turn the engine over to see that there are sparks on all 4 plugs. If so, your black box is most probably fine. The move onto the carbs. It's surprising how much filth they can accumulate

[CatatonicBug]

What vac line is that? Coming from where?

Yeah.. That sounds a bit strange. If you have no Octy, the vacuum ports should ALL be blocked off. You don't want to be sucking fuel (albeit accidentally) into the intake through the vacuum ports!

[jetmechmarty]

He said the bike is a '79 standard. So, it has no "octy", but two vacuum petcocks. Am I right?

[CatatonicBug]

He said the bike is a '79 standard. So, it has no "octy", but two vacuum petcocks. Am I right?

Oops. Good point. Helps if I actually read all the words...

[Ken Talbot]

He said the bike is a '79 standard. So, it has no "octy", but two vacuum petcocks. Am I right?

He said the bike is a '79 standard. So, it has no "octy", but two vacuum petcocks. Am I right?

Oops - that is what he wrote, but I made the leap in my mind to his previous ride "Yellow Zonker" which was a Special.

While you're at it, Syd, be sure to check the operation of the petcocks when they're not hooked to the carbs. Each one should flow for 'on' and 'reserve' only when vacuum is applied to the smaller nipple on the petcock body. Fuel shold flow for 'prime' whenever the lever points that way.

[s clarke]

XS11 Std problems

Ken, yes, after rebuilding/cleaning/setting carbs today..(all good), checked fuel flow, and worked as they were suposed to. Bike started well,ran really 'clean', for about 3 minutes, then 'pop pop, miss, black smoke, pop, bang, at which point I shut it down. Took side cover off, checked wires carefully, no breaks, rechecked coils for ohms, and spark, good. Refired it, ran smmoth as Silk, for about 20 seconds, then started that whole 'popping/smoke" thing again. Will take "black Box' apart tomorrow and check, and then try to find where I 'hid' my extra boxes ==*^( If you have a good one from a Std, could I "borrow' it just to see if that eliminates problem, or point me to a place I can buy a new one from) ??
Cheers
Syd

[Ken Talbot]

Took side cover off, checked wires carefully

Still sounds to me like it may be pick-up coil wires. When you check them with the motor running, you can actually be quite vigorous as you're tugging on the various wires. If you can pull one apart with just your fingers, it was already broke and waiting to fail again. Think of it as if you were trying to pull apart a fresh length of that type of wire with your bare hands - it isn't going to happen. Also, be sure to pay close attention to the crimp fitting that secures all four of the wires together just before they exit the engine case. Loosen the crimp, and do some more tugging.

[SFerinTEXAS]

What vac line is that? Coming from where?

Humor me please.Where are the fuel valve vac lines hooked to?

[DiverRay]

I would start at the top, Cam chain adjust, Check valve adjustment, double check float height, and VERIFY OFF THE BIKE that the needles are working, then put carbs back on. Fuel petcocks connected, with vacuum line from #2 and #3 BOOT to petcocks.
Fire engine, adjust idle mixture, sync carbs, re-adjust idle.
It seems to be flowing too much fuel, so I would also check the upper lines that go from the carbs to the airbox, and make sure there is no blockage.

[skids]

Hey Syd, glad to see you are back! I hope you get her running in prime form again.