Poor running and plugs fouling... jetting or elect

Hello, I need help with the 1979 kz 650 that I've just buyed... I'm posting here because I don't know if its a jetting or electrical problem!

When I bought it, the bike would exhibit a huge bog in the midrange while cold, which got slightly better when fully warmed up, but still very poor performance...
P.O. claimed that the bike was running fine but since the carbs were leaking fuel he took it to a mechanic who disassembled the carbs to clean them, synch them, and install a carbs revision kit (jets,needles and gaskets); after he took the bike back from the mechanic, it started to act like above, with the big bog in the midrange until hot.

He addressed this problem with rich jetting, also because he was fouling plugs frequently and the petcock was leaking fuel. From my experience instead, the bog while cold was a symptom of lean running!
So i tried to richen the needles ( they were in the stock position, 4th slot from the top, put them in the 5th) and the bog disappeared! Bike was running strong, almost perfect, so this confirmed that it was previosly lean... BUT, after just a day of city driving at very low revs, the plugs fouled themselves... so needle in the 4th slot is too lean and the bike runs awfully, in the 5th slot is too rich and will foul plugs at low speed !

The Odd thing is that even when the bike is clearly running lean, bogging like its missing gas, the plugs are always sooty black!! this is why I suspect an electrical problem...

Tried everything, here is a summary of the situation:

- Clean tank with fresh fuel

- fixed the petcock with new orings

- Stock airbox and exhaust

- Carbs where indeed very clean when I disassembled them, but I'm wondering if they could look clean but have obstructed passages... i blowed air through the main jet, pilot jet, and randomly through all the carb... what should i look for?

- synched the carbs

- 102 mains, 15 pilots, stock needle in 4th - 5th slot. Tried 110 mains leaving needles in 4th slot and it runs way too rich, doesn't go past 5k rpm.

- Float level wet checked at 4mm

- new b7es plugs (buyed 2 sets until now...)

- adjusted valves

- Timing adjusted with static method; points were pitted sanded them down but still have a little pit... timing advancer does move freely and smooth ( how can I be sure this is operating correctly? )

- blade fuses mod

- voltage to coil is very good: 12.2 V , with 12.4 V at the battery terminals. Tested the coils: primary windings show 4.4 ohms, secondary shows 14.9 K ohms (spec is 23 k ohms... bad coils? ) . Spark doesn't seem very bright...How can I test the coil output to the plug caps??


With the needle in the 4th slot the bike its nearly undriveble, when you open the throttle it feels like the petcock is closed for some time, until 4-5k rpm where it suddenly starts to pull to redline normally.
If I put the needles in the 5th slot instead,the bog disappears and it runs strong but rich, and fouls plugs after few minutes of slow revving...

But my main concern is that the plugs are always dry sooty black, even with stock jetting and bike acting lean... seems like it cannot burn fuel efficiently!

What should I do?? its driving me mad...
ANY help will be very apprecieted !!

I recommend you buy the Kawasaki Service Manual, become familiar with the engine maintenance tasks, and perform a full tuneup. If you are using the stock airbox and the stock jetting in the carbs you have some other issue causing the problems you describe. Performing a full tuneup will set a baseline from which you can try to diagnose the problem. In fact, the full tuneup may even eliminate the problem. Be sure to get the manual for your exact year and model as there are significant differences between KZ650 models. Ed

Pics of plugs.
Steve

THanks, I already have the sm , did a tune up of the ignition (static timing) , points gap, carb cleaning, carb synch, checked the wiring harness and coils...

will post pics of the plugs

I saw a photo of your bike on another site. It does not look like a 1979 model to me. It appears to be a 1977 KZ650-B1 with wheels from a different model. It definitely has the 1977 charging system. Ed

yeah sorry its indeed a b1 model with 3 phase ignition!

When I tested the coils secondary winding yesterday, i measured between plug leads with the caps off, and measured 14.9 K ohms which sounds ok (tester on 20k ohms setting) ... Today I tried to measure the secondary winding with the plug caps ON, and the tester couldn't read anything on either of the two coils !
So I thought that maybe the plug caps are bad! Tested the caps individually , three coils measured each one different from the others: one 6 k ohms, one 10 k ohms and one 16 k ohms ! the last one didn't show any reading (tried every tester scale setting).
Could this be my problem?
I'm gonna buy some new plug caps just to be sure!

I would, they go bad after a while. Get non resister.
Steve

Buyed and installed new ngk 5kohms plug caps, it seems that this was the culprit!
Bike now runs much cleaner and the plugs does not get black and sooty... actually they are now whiteish , just to confirm that the bike is lean , as i suspected!
Thanks to everyone for the inputs