Topic: Cylinder not getting hot

[Little_Phil]

If original coils, did you clip off 1/4" of the plug wires to give good connection to the plug caps? Did you test the plug caps resistance?

If original coils, did you clip off 1/4" of the plug wires to give good connection to the plug caps? Did you test the plug caps resistance?

It's a wasted spark system, so if there is no spark on three then there will be no spark on 2.

Going back to this, you can get a spark on one cylinder if the other line of the HT is open circuit. Just had mine running on three with one HT lead well clear of earth.

[rotortiller]

It's a wasted spark system, so if there is no spark on three then there will be no spark on 2.

Curiosity got the better of me so I removed No1 spark plug cap, then removed No4 cap and hooked it to a new spare plug grounded to the engine due to easy access.  It sparked fine on my 750K7.

[willbird]

It's a wasted spark system, so if there is no spark on three then there will be no spark on 2.

Curiosity got the better of me so I removed No1 spark plug cap, then removed No4 cap and hooked it to a new spare plug grounded to the engine due to easy access.  It sparked fine on my 750K7.

It has to be completing the circuit SOMEWHERE :-), maybe not a good place :-).

[rotortiller]

I know what the diagram says which kinda says it shouldn't do that. My bike works fine and it does what it does, just like others have observed. It's enough that it works lol.

[willbird]

I know what the diagram says which kinda says it shouldn't do that. My bike works fine and it does what it does, just like others have observed. It's enough that it works lol.

The "lose two  with ignition problem" is still a good general rule though.

One pipe cold for me so far has always been a carb issue. No fuel in the float bowl, pilot jet vibrated loose and fell into the bottom of the float bowl, etc. One plug gap totally closed can give you one cold cyl tho :-).

This situation right here can cause some weird stuff until you find it and fix it :-).





Bill

[TwoTired]

Current flows in a loop. Once voltage rises high enough to jump a spark gap(s) and form a plasma channel, it requires current to sustain that spark event.  Insulation is not absolute.  If the voltage is high enough, it will simply pass through it at the lowest resistance point (crack or thinned portion), finding the lowest resistance path back to complete the current loop. 

If you disconnect a lead and still get spark on one of the pair of plugs, the spark current path found an insulation weak point.   Broad daylight can hide where that is.  And if it is passing though the insulation, it "remembers" that point for future escape and weakens the insulation at the point of escape, usually by vaporization in the arc channel it formed.

There is also the possibility that as the spark lead insulation ages and hardens, it loses some insulation value and is less able to contain a voltage and current that normally finds an easier path to complete the current loop on it's center conductor.

While High Voltage may appear to bend the rules, it actually has defined physics to which it adheres.

[Mark K]

Pulled #3 carb pilot jet, completely clogged, unable to get it opened up. Replaced pilot jet w/same size from rebuild kit. Replacing the pilot jet fixed the cold #3 cylinder issue.

New problem, #2 carb overflow pouring fuel, just like #3 carb did, will reinstall old float, that fixed the same issue on #3 carb.

Ran the bike for about 15 minutes (w/2 fans blowing on the engine), engine idling between 1100-1300rpm. Used an IR thermometer to 'read' the pipe temps, 2-3" from the exhaust port.

Exhaust pipe temps
#1 - 182*F
#2 - 179*F
#3 - 177*F
#4 - 108*F
Checked each one numerous times and kept getting 108*F on #4 pipe.

Pulled the plugs, gap still set at .026" All plugs looked black and sooty. I cleaned the plugs after pictures and reinstalled. Plugs are basically brand new NGK D8EA, engine has only run for about an hour total time since rebuild, have gas tank issue trying to work thru, as well as the other issues.

Suggestions as to what's going on are highly appreciated.

Pictures of the plugs