I've a recurring problem with the bike dropping the right cylinder. The bike runs fine, then it will suddenly drop the right cylinder. It will run like that for a while and then stop altogether. Generally the bike will then start again running on both cylinders.

I've replaced the plugs, swapped the coils to the other side with no apparent difference in it's running, I only started the bike up and didn't take it for a ride.

Could the problem be the pulse generator pickups? I tested the resistance of it and it tested OK.

Intermittent problems are a pain ... wouldn't you agree? 

Given the checks you've done, it doesn't sound electrical.  But if nothing else pans out you might want to make/buy a [spark checker] so you can visually see whether the spark "quits sparking" at the same time the cylinder goes out.

Meanwhile, let's check the fuel side of the combustion equation.  My hypothesis is that fuel isn't being supplied to the right carburetor fast enough to keep up; that the input path to the float bowl is partially blocked somehow.

* After sitting for a while, the right cylinder works OK.  Fuel could have filled the bowl at a slower-than normal pace.

* Since the bike runs well for a time, I don't suspect problems in the jets themselves.  When fuel is available, it seems to be metered correctly.

* The right cylinder eventually stops working.  Fuel starvation?

The easiest test I can think of is to:
    1) put the bike on the centerstand, so the left carb has no "downhill advantage"
    2) flip the fuel selector switch to PRI
    3) open the drain screw on the left carb (catch the fuel in a container!)
    4) watch the fuel drain for a while, to get a feel for the rate of flow
    5) repeat on the right side

Is the rate of flow the same?  Does it ever slow down?

Check the ignition pickups under the right side cover.  Intermittantly dropping only one cylinder is usually an ignition fault to me.  By changing plugs and swapping the coils you've isolated it to the pickups and the secondary circuit wiring.   

I guess it could be temperature-related.  Can you set things up so you can repeat the signal generator pickup resistance check right after the cylinder stops working and you turn off the bike?

How I know it's spark related, when the bikes been playing up I pulled the right plug cap off and the bike ran the same. I pulled the left one off and the bike wouldn't start.

I thought temperature as well, but yesterday the bike started playing up after about 6kms (4miles) 

I'll check the wiring for from the pickups to see if theres any bare wires or breakage's. I'll also get a price on a new set of pickups. 

The funny thing about this problem, is that it only showed up after I repainted the bike.

And Kerry intermittent problems are a PITA 

how is the humidity in the air as well , just and idea damp dry ect youy get the picture???

Quote from: bubba zanetti on February 12, 2008, 12:31:59 PM


The funny thing about this problem, is that it only showed up after I repainted the bike.

That suggests the possibility of a poor earth connection to me.

My friend's GS was doing that, using a multimeter and starting at the signal generator, we found a wire wasn't showing continuity. Pulled a few connectors apart and found that because the PO had installed the wrong battery, then didn't attach the little drain hose, the battery had corroded this wire.... and it propagated WAY down the wire. We had to cut a good section out of it and replace because it was so rusted we couldn't solder anything to it! There's really not that many wires to check, maybe give that a  shot?

I've taken some measurements of the signal pulse generators with this problem happening. One pair of wires were at 420 and the other were off the scale. So it looks like the problem is the signal generators.

BTW I was reading some old posts by Kerry about this problem and they were very informative. 

Yesterday I replaced the the triggers for coils and took it for a run today, just like a brand new bike.

Once again I like my bike. 

Quote from: bubba zanetti on February 12, 2008, 12:31:59 PM
How I know it's spark related, when the bikes been playing up I pulled the right plug cap off and the bike ran the same. I pulled the left one off and the bike wouldn't start.

I thought temperature as well, but yesterday the bike started playing up after about 6kms (4miles) 

I'll check the wiring for from the pickups to see if theres any bare wires or breakage's. I'll also get a price on a new set of pickups. 

The funny thing about this problem, is that it only showed up after I repainted the bike.

And Kerry intermittent problems are a PITA 

If you pull the plug wire on the dead cylinder and and see no change in running, that does NOT indicate an ignition problem.  The only thing that indicates is that the dead cylinder is definitely NOT running at the time.  What needs to be done is you have to ground the plug wire out.  If there is a noticeable arc to a solid ground, then it's an mechanical problem.  If there is no spark, then it's electrical.

Be it either way...dead cylinders in my experience have ALWAYS been either poor compression or stator/charging system related

I did check for spark when I got the bike home by running the bike with a spare plug out of the bike and there was no spark on the right cylinder.