Lost number 2 cylinder

[TopCatGr58]

If I switch plug wires 2 & 3 on the coils to narrow it down to #2 carb do I need to switch the wires from the harness that plug into the vf1000 could as well?

Hey there, Don't mind those two, they do get a bit grumpy every now and then!

Okay, each coil fires both wires at the same time for that respective coil, so that's why you can just switch the 2 and 3 plug wires/caps to opposite cylinders, and will fire correctly. This technique is to see if the problem is Electrical...the problem will follow the wire and # 3 will start having problems and misfiring. BUT if it's a CARB issue, then #2 will still be problematic, and the #3 will continue firing as usual.

Fuel in the carb throat/air box is signs that the carb is still flooding, which can fuel fowl your plug and cause the miss. You say you checked the needle/seat. Aside from a piece of crud getting stuck/wedged in between the needle/seat, the actual float can also just get HUNG UP/stuck for several reasons. Either corrosion on the float PIN so that it doesn't swivel properly/easily, or even a new thick/wide bowl gasket that catches the side of the float keeping it from moving.

Also, did you clean the carbs, and did you use a Carb Kit ie. K&L brand??
Their parts are known to cause problems/issues, the float needle is designed wrong and can allow the flaot not to seal properly vs. Original Mikuni parts.

IF the pick up coil wires were breaking, they usually cause a miss in 2 cylinders because they cause an entire coil to loose fire, not just 1 plug!

From what you've stated, my money is still on problems with the carb/floats more than the wires/coils....VF1000 coils are just fine!

There are other more rare conditions that can cause loss of spark on just 1 clyinder....ie. the resistor in the plug cap can go bad, or get too much corrosion on it causing it to not fire, or fire with very weak spark.

T.C.

[James England]

Fuel in the airbox says it all. You have a stuck float and/or float needle on number 2 carb.

[motoman]

Fuel in the airbox says it all. You have a stuck float and/or float needle on number 2 carb.

+1.........pull that airbox off and rearward.......turn fuel on a look to see if fuel is runnin' out of #2 carb. Do NOT try and start with airbox off! a backfire through carbs could and WILL ruin your day, and maybe the man-cave and house.

[James England]

+1.........pull that airbox off and rearward.......turn fuel on a look to see if fuel is runnin' out of #2 carb. Do NOT try and start with airbox off! a backfire through carbs could and WILL ruin your day, and maybe the man-cave and house.

agreed. I had an XS catch fire doing that. Outside fortunately, and I always have a small fire extinguisher handy when working on bikes. . .

[motoman]

agreed. I had an XS catch fire doing that. Outside fortunately, and I always have a small fire extinguisher handy when working on bikes. . .

Glad to see someone has had the personal experience.............was beginning to wonder..........Oh!.........let's not forget the one who fried his closed front porch area and almost the house............and of course, can't forget SpecialEds maltov Special..........on and on.









special

[DiverRay]

and of course, can't forget SpecialEds maltov Special....

Hey, he was outside, and just secured a loose fuel line. Never mind that the RC Engineering engine liked to backfire on startup....Oh, and he DID have the air cleaner in place.

[XS1100_OEM4ME]

Fuel in air box

Went for a a ride yesterday about 5 miles. Started back and number 2 began to miss fire. Got the bike home and pulled the plugs out number 2 was soaked with fuel. There was also fuel in the bottom of the air box. Cleaned the plugs and spun the engine with the plugs ground in the fins and got strong spark on all 4. Pulled the carbs out checked for obstruction in number 2 needle and seat nothing to be found. Put it all back together after checking the carbs still had a miss fire on number 2. I put dynatek wires and new vf1000 coils last year. All floats set at 23mm. This all happened suddenly while I was entering the highway under 3/4 throttle. Any ideas or input would be greatly appreciated. This has never happened before.

I read some of the advice, here is mine for what it is worth, I don't care if a plug stopped working. If it was soaked with fuel and you had fuel in your air box, you have a fuel delivery problem. That could be a stuck float or many other things, but it is fuel related and not electronic JIMHO

[motoman]

Kind of why my replies get pissy after a while and I am not on here as much lately. Owned and worked on an XS1100 since 1979.... Might know a thing or two. Heck the mechanic that assembled my 79 special has me rebuilding his carbs now. By the way he is still a motorcycle mechanic, but he now specializes in HD's.
Oh well. We shall wait and see what the solution is...eh!

Can't agree with ya' more Rasputin.........been previously turnin' wrenches in the car performance world long before I bought my still owned Venturer 1100 new.

[motoman]

I read some of the advice, here is mine for what it is worth, I don't care if a plug stopped working. If it was soaked with fuel and you had fuel in your air box, you have a fuel delivery problem. That could be a stuck float or many other things, but it is fuel related and not electronic JIMHO

.........Gotcha'............electrical(secondary ignition) BEFORE fueling,........ALWAYS.

[XS1100_OEM4ME]

What?

.........Gotcha'............electrical(secondary ignition) BEFORE fueling,........ALWAYS.

Don't quite get your response. Fouled spark plugs and gas leaking from air box? "Gotcha' electrical (secondary ignition) BEFORE fueling?????". If my brake fluid spray's out on my bike and my bike won't stop, should I check my brake pads first

[motoman]

Don't quite get your response. Fouled spark plugs and gas leaking from air box? "Gotcha' electrical (secondary ignition) BEFORE fueling?????". If my brake fluid spray's out on my bike and my bike won't stop, should I check my brake pads first

.........maybe wanna' change your britches first, as they'll at the least be soaked with brake fluid.........then hang in there another couple decades, you'll catch on to the other part of what I stated.

[XS1100_OEM4ME]

Air box

IMHO, if your air box is full of fuel you might have a fuel problem. If so, and one or more of your plugs gets fuel soaked and stops firing, you still might have a fuel problem

[James England]

As I said before, the key factor here is that the airbox is full of fuel. It is virtually certain that the needle valve is stuck or malfunctioning...it could be the needle valve itself, or a stuck float or whatever but the point is, the airbox is filling with fuel. The fuel is going backwards into the airbox but also going forward into cylinder number 2, soaking the plug and stopping it from producing a spark. It's highly unlikely that the plug or indeed that whole electrical circuit, both low tension and high tension, has a problem. Yes, the plug is not sparking (not exactly surprising, given that it's drenched in gasoline non-stop) but that isn't actually the cause of the problem, IMO.

Airbox full of fuel = carb needle valve not closing properly/at all.

So.... first of all fix the clearly obvious problem of non-stop gasoline intake on at least one carburettor........ I'd say that's more urgent that mucking about with wires for now.

OK, done that. Ooo...let's see if a nice clean, dry plug produces a spark on the suspect cylinder by laying it on the head and turning the engine over...... spark? Yes = guess what no ignition system problem. No? there's a problem with the ignition system but......guess what?......

at least the fuel peeing through an improperly closing needle valve is now fixed!