KZ1000J3 Starting on 3 Cylinders After Sitting

Hello,
Just wondering if anyone has any insight on this. My J3 is starting on 3 cylinders now at start up (one on kickstand side is not firing) after the bike sits for over a week or so. After I cleaned the plug on the kickstand side it runs on 4 just fine. Sometimes it will resolve itself on its own. When I pulled the plug today it had a black soot appearance. Before I start it next in a week or two, I will verify the condition of the plug before I start the bike and not after which may tell us something. Just for reference over the last two years I have installed a new OEM ignition system back to the battery from the plugs, new battery, new plugs, new boots, rebuilt carbs, the carbs were ultrasonically cleaned and the petcoke was rebuilt. The bike has new gas in it. Any thoughts on what is happening here would be appreciated. BTW I but a small block under the stand so the bike does not tilt so much when sitting. Also should I be concerned about gas in the oil at this point assuming some may have leaked down when bike was sitting or running for a short time on 3 cylinders. Fyi, I do not smell gas at the exhaust.

Thanks

Do an ohm check of the sparkplug caps, They have a 5000 ohm resistor for RFI suppression. To do this test, unscrew the cap from the sparkplug wire, set the multimeter for OHMS (looks like an upside down horseshoe), range of 20K. Put one probe inside where the sparkplug went, and the other probe that went on the sparkplug wire area. If the resistors good, the meter will show the resistance.

If the caps check good, before reinstalling them, cut about 3/16" to 1/4" off the end of the sparkplug for a better connection.

A video on using a multimeter:

The best multimeter tutorial


I may have missed it, but did you replace the ignition coils? Even when new, they were marginal, and after cooking under the tank in stop and go traffic, they can fail when hot. Dyna 3 ohm and Accel 3 ohm coils are a good replacement.

Alternatively, If you swap the outer HT lead and plug from pot 1 over to pot4, and the problem doesn't transfer to pot number 4, you can eliminate ignition,
Harder to test intemittent faults like this I know.

A lot of carb problems manifest themselves on pot 1, rust sediment from the tank not caught by the petcock strainer finds it's way here when bike is 'asleep' on it's side stand. Your sooty and wet plug could be a float bowl overfilled.
See my other reply on fuel filters for the big hammer easy fix;)

Thanks. The tank is NOS only 4 years old (sat on a shelf for 27 years). It is silver inside. OEM coils, wires and ingnitor were installed. Since all work was done within the last year to two I have only put on a few hundred kilometers max. on it. Bike is basically a garage queen.

Today was the first time I pulled the plug after riding around the block. It was black and sooty as mentioned. After I whiped it off - pulling off some soot but when put back it was still black, the bike turned on 4 cylinders immediately and I went off on my ride and it ran very strong. Personally I think the plug in question is getting wet when the bike sits on its side and is not firing on ignition.

Your plug shouldn't be wet - see what I wrote on the other thread for an easy fix, otherwise a carb overhaul may in order.

Had just this problem on my Lawson rep.

Even worse, if the pot is filing with fuel you can damage the motor as fuel doesn't compress like fuel/air vapour... I've even heard of bent conrods on motors caused by this but not seen it myself.

Thanks I will check the thread. I should have mentioned and will update the first note, the carbs were also rebuilt in this time. BTW I am suggesting the plug may have been wet before the bike started - will have to wait another week to see.

Just an update. I took the bike to a reputable shop to look at the problem with spark plug #1 not firing if the bike sat for a while. A compression test was done and all was fine. Carbs were opened up also. When carbs were previously ultrasonically cleaned, the pilot jets appeared not to have been removed and passages cleaned - they were dirty. This was deducted by the mechanic understanding the condition was the same in each carb. Everything else was clean. In addition float levels were adjusted for bike to run leaner and the plugs were replaced. Everything else in the carbs apparently looked good from original rebuild that was done last year. Bike runs like a top!