Misfiring KZ650

I need help, I know quite a bit about cars but motorcycles are completely new to me, also this is my first bike! I have a 1979 KZ650B and it is misfiring or I am assuming it is because it will pop and crackle. The issue wasn't that bad when it was colder out and I was riding in 35 degree weather, but today it is about 80 degrees and I do not feel safe driving it because it is now misfiring at higher rpms and it is surging and a significant loss in power.

My first thought was that the timing was off or something. I do not have stock ignition points but I looked at what I have and moved it to the "T" mark and it got a little better but still misfiring. I also don't know if the carbs are synced.
I do not know what I should be looking for anymore. I have been looking at the service manual for help but no luck.

Any help from you guys on where to start would be greatly appreciated.
here is what one spark plug looked like:


The other three:

That is a great bike, I have owned my 78 KZ650 since new and it has never let me down, you will have a blast on it. First thing is read your manual for the bike and do a complete tuneup. That will include adjusting the valve clearance, changing the oil and filter, ignition timing, ect.. That will give you a good base line to tune from. Never try and tune a "new" bike without first making sure the basic tuneup is done and within specs. If you try and do that it will lead to much frustration because things like tight valves will show symptoms of a carb problem when in reality it's a valve clearance issue.
Does the bike have the stock air filter assembly, what exhaust system is on it, has it been sitting for a long period of time with gas in the tank and carbs. Looking at your picture it looks like someone swapped in a later model IC ignitor ignition system, good upgrade. The "T" mark is not the firing mark it is the "top dead center" mark. The firing mark is an "F" just past the "T" mark while rotating the engine clockwise.

Yes the F mark is for ignition timing, the T mark is for cam timing. If the T mark is used it will be retarded and run rich. thus the black plugs. The clean electrode suggests "washing" by fuel. Might be a little oil mixed in but might clear up when it running right. Use the F mark and get back to us.
Steve

I will have to buy a manual but in the mean time is there a free online manual I can use? It is a stock air air filter and box. It has not been sitting for a long time but I did clean the carbs and just ordered a rebuild kit. When I did adjust the IC ignitor I didn't and improvement with the misfiring. I will have to switch it to the F mark but I will be doing a full tune soon. I will get back to you guys later tonight with the results. Thanks

Alright I moved it to the "F" mark and still nothing happened.

Are valve clearances within spec? Too tight clearances can result in loss of compression when the engine attains normal operating temperature, resulting in sooty plugs.
A standard compression test showing acceptable figures doesn't automatically mean that the valve clearances are correct.

Would also remove the plugs and hopefully see fat blue sparks while spinning the engine with plug bases grounded against the engine head.
A weak ignition with thin orange sparks may result in incomplete combustion which results in sooty plugs.

And would perform the clear-tube test on each carb to determine if fuel levels are within spec. Because, even with otherwise perfect carbs, a too high fuel level may produce an excessively rich mixture which results in sooty plugs.

Good Fortune!

I checked the valve clearances today and almost all of them measured to be less than .06 mm , so I am purchasing a valve cover gasket and a shim set and I'll get back to you guys when its all installed

I had to bring it into a local shop, because the shim I needed was sold out everywhere and they wouldn't sell it to me individually, only in the service. Apparently they put the smallest shims they had in there and they could only get their smallest feeler gauge in there. except for the #3 intake. So this winter I will be rebuilding the heads. any suggestions where I can get new parts for the rebuild?

I think you need to start over from the beginning.

Step 1 - Determine for sure without a doubt, which model motorcycle you have and which model engine is in it. You can do this by using or posting the frame number stamped on the steering neck and the engine serial number stamped near the oil filler cap. Then determine what modifications have been made. Until you have done this you will not know which manual(s) to buy.

You mention in a posting above that the bike has an "IC ignitor" and you indicated that you understand this is not stock. You are correct; it is not stock, so what was the unit intended to be used on, is it even compatible with a KZ650 engine, and are all the correct components (such as coils) in place and compatible with the ignition system and with the engine and its charging system? Your engine is misfiring and your ignition system is not one that came on the engine - it seems obvious to me that there could be a connection since the ignition system controls the firing of the plugs.

Step 2 - Buy the Kawasaki Service Manual for your bike's exact year / model. There are big differences between the various KZ6750 models so buy the correct manual is essential if you are going to be successful. After buying the manual read through every section carefully. This will give you a much greater understanding of the bike; how each system on the bike works; and what maintenance should be performed.

Step 3 - Assuming the modifications ARE NOT compatible with your bike; take action to replace those that are a problem.

Assuming the modifications ARE compatible with your bike - perform a full tune-up. This will provide a baseline from which to determine if the bike has problems. Along with adjusting the carbs, new plugs, etc., etc, the tune-up includes adjusting the valves if that is needed. Do not automatically assume you need to rebuild anything. The fact that the shop put in the smallest shims they had in their junk box (if they even did) doesn't mean squat. Regarding valve adjustment the questions to be answered are A -What are the current valve clearances when PROPERLY measured; B - what shims currently are in use; C - what shim sizes are required to bring the valve clearances within spec; and D - are those size shims within the Kawasaki Valve Shim Adjustment Chart. If they are in that chart - you can get them; you just need to find them. If the valves are so far screwed up that they can not be adjusted using shims (VERY UNLIKELY) determine what actions need to be taken.

It is very likely that performing a full tune-up will correct the problem the bike is currently experiencing. If, however, after performing a full tune-up there still are problems they will be much easier to diagnose because many variables will be removed from the trouble-shooting process.

You should understand that the stock KZ650 engine is extremely reliable and nearly bulletproof, so all but the most abused or extremely high mileage engines do not normally require extensive internal repairs. Ed

I tried to find out what model I have but I had no luck. The frame isvKZ650B-531177 and the engIne is KZ650BE 106991. Once I figure out the model and yeat I will buy the manual. All the plugs had big blue volts. I rebuilt the carburetors and tuned them myself and it is running a lot better. still needs a few adjustments but the misfire at idle is gone. But I completely agree with you 650 because the place I got it serviced at was very shady, they told me it would take a week, a month and I week later I called them multiple times til they finished it, the mechanic was unable to tell me the size of the shims in there. before I took it for a ride I check their work and two bolts were not even screwed in. This winter I will be going over there work its just that it irritated me. Thank you 650 for the help along with everyone else

The numbers you posted fall with the range used on the 1979 B3.

1977 KZ650B1
Japan: Frame 000001-026990
Engine 000001-045147

USA: Frame 500001-508015
Engine 000001-043949

1978 KZ650B2
Japan: Frame 027501-032200
Engine 046001-057787

USA: Frame 508016-515325
Engine 046001-057787

1978 KZ650B2A
Japan: Frame 033501-044828
Engine 061299-090685

USA: Frame 515326-523523
Engine 061299-092000

1979 KZ650B3
Japan: Frame 046201-047350
Engine: 092001-102148

USA: Frame 523524-533520
Engine 092001-116800

Do you have the air injector on yours? Vacuum leaks can cause popping with them too.
Styeve