No spark to cylinder 3?

dannyh, sorry if I misunderstood your earlier posts. Blue spark is good. Regarding the carbs - I once rebuilt carbs 3 times and still had problems. Left it in a shop and paid to have them done, Still had problems. Only after my 4th attempt did everything work the way it should. Regarding the float bowl height being low I think it could effect the running of the cylinder by making it run lean or at worst not running at all. Might be worth revisiting this and setting correctly.

I might hav found out one of the problems. I completely swapped out the # 3 and 4 wires. Still no change. However, I turned out the lights in my garage and started the bike. I disconnected the wire from #3 and could see little sparks jumping from the wire to various things. I then held the spark plug boot and saw little sparks jumping from the boot to my fingers. They were small enough that I couldn't see them with the lights on or in daylight. I couldn't feel them either. But I definately saw them with the lights off. Keep in mind that thosse sparks were going through the boot of the previous #4 wire, now #3. That is bad, right?

So... where can I get new wires and boots? I called my local Kaw dealer and they said they don't sell wires seperately. They only sell them in a package with a coil.
Can you fabricate them yourself? I really don't want to buy a coil, since I know mine is good.

Also what will happen in the meantime if I ride it around on three cylinders? Will it permanently damage the cylinder?

Danny...while the bike is running...try spraying some WD40 directly into the air-side of carb #3 and see if it idles any differently.Anything flammable will work(carb-clean,or brake-clean),but I like to use WD40
If it does idle differently(higher),then You know it's the carb.It sounds to Me like it IS the carb itself,so give that a try and see if it makes a difference...

Has anyone figured the solution to this? I recently just came up with the EXACT same problems as him. I got a 79 KZ 1000 ST, and the #3 cylinder is dead. It's got spark, fuel, and air. I've swapped out with new plugs numerous times, I've cleaned the carb rack, I've swapped 2 & 3 coil wires, and adjusted the screw on the carb, ALL which had no effect on the bike. I am absolutly stunned trying to figure out whats wrong. I thought maybe its possible the spark is hopping from the plug wire to the frame, bypassing the plug completely? Does this sound feesable? The only other problem I thought it could be was a dead cylinder, but I did a compression test and it came back with 120 psi. So everything looks good, but its still cold. Read my words, I WILL figure out what is wrong with this thing if it kills me!

A spark plug with an internal short can be the cause of your problems. Try putting in some clean, properly gapped plugs you know are good, and see if it makes a difference.

All of Danny's "tests" and conclusions have me a bit confused so I will put down some GENERAL steps for troubleshooting this issue. If any of these have been covered, I would still retry them in the order given so that these can be totally ruled out. I suggest testing to see if a plug is firing by taking a spray bottle of water and spraying the pipes after they have had a chance to warm a bit. After about 30 seconds, a hot pipe will vaporize water while it will run down off one that is mearly getting hot from proximity to the hot pipes but the cylinder isn't firing:

1. Compression check with gauge on all cylinders - Low compress WILL cause a cylinder to not fire. The MOST repeat MOST common reason for lack of compression is that a valve (or valves) have NO clearance and are partially open - this leads to FOULED plugs which will also cause the cylinder to non-fire

if compression checks OK then step 2

2. Electrical issue. If ONE cylinder is not firing, this imples the coil is OK but either the plug, plug wire, connection to the coil or the plug cap are at fault. FIRST - The coils fire in pairs. If #3 isn't firing, swap the #2 and #3 plug wires. If the problem remains on #3, then REPLACE or SWAP the spark plug. A bad plug DOES happen. If the problem moves, then check the seat of the plug wire in the coil. Remove the wire, cut off perhaps a 1/4" and reseat it. If that doesn't fix the problem, replace the wire and cap.

If this doesn't fix the problem, go to next step:

Step 3 is carburetors. Put in a clean set of spark plugs as the plug for the non-firing cylinder is likely fouled from the non-combustion. Start the engine and then rev it to perhaps 4K rpm. If the bike doesn't idle but "cuts in" when rpms rise, the pilot circuit has blockage in either an air path or fuel path. Clean the internal passageways completely and retry to see if the cylinder has combustion (water test on pipe) at idle. If it doesn't you might need professional carb help since whatever was doesn't didn't work. If the bike doesn't "cut in" when you rev the engine, reset the float level using the Service Fuel Level method (set the float level WET). There is little liklihood that the #3 cylinder fuel pipe is obstructed if #4 is getting gas. If the problem occurs on an OUTSIDE cylinder, there is the possiblity that the fuel pipe itself is plugged or obstructed. Another thing to check is that vent ports are free and unobstructed and that the carbs are drawing gas easily as there is no vacuum lock. In other words, if the vents are open, gas can be locked in the tank if the tank vents are plugged. Try opening the tank gas cap when the bike is running on 3 cylinders to see if the cylinder kicks in and starts running. It could be that one carb's float level is a shade low and the bike is having problems drawing in gas. The last thing that is unlikly but possible is that the carbs are so far out of sync that one carb is getting almost NO engine vacuum at idle but even then, all four cylinders should kick in once the slides are raised when revving the engine.

Well here is the status. I bought new plug wires and took the carbs off again just to check everything and adjust the float bowl level in #3, which was a little low.
It started right up, but is very difficult to start after it is warmed up. Does anyone happen to know what would cause that?
The #3 exhaust pipe still does not get as hot as the others. I can grab it after it has been running a while. While riding around I open it up and it accelerates well. I am going to ride around at a constant 4,000 - 6,000 rpms to see if it fires at higher RPM's.

The thing that baffles me is that I can pull the plug wire off #3 spark plug, not arc it to the block and the bike runs the same. That makes me believe that that it is arcing or completing the circuit somewhere else. I am going to take the completely swap the left and right coils to see if the problem persists.

I really need to do a valve clearance check and compression test. When it is all said and done it still sounds like a carb issue.

I have read wiredgearge's latest post and I am going to do all of that as well. Any other suggestions?

Danny, When I suggested adjusting your valves, keep in mind that I rebuild, tune and test about 300 sets of carburetors (just like yours) a year and work on bikes for a living. Perhaps it is a carburetor issue? If so, I was out of line for suggesting the steps I did and apologize in advance for wasting your time on stuff unrelated to your actual problem. After all, its your bike and you are not really obligated to follow the advice you asked for. Good luck!

No appology needed. I probably need to do a compression check anyway. Since I don't think it is an electrical, it has to be a carb or a compression issue. It is easy to slap a compression gauge on the cylinder and check the compression. If is is bad compression then it is probably due to bad valve clearance. The inside of the cylinger is pretty clean which would suggest the piston rings are still ok. So a compression check is in order.

I have ruled out electrical issues. I have swapped the #2 and 3 wire connections to the coil. No change. I have also swapped the plug out. No change.

So to shorten this up. I will do a compression check and if everything checks out, then it is back to the carbs.

Speaking of which, does anyone have any suggestion on how to get the throttle pulley mounting screws out of the throttle shaft in the carb? Mine are really stuck. I don't want to strip the heads trying to get them off. I need to get them off so as to replace the main needle. It is the only thing I have not replaced in the carbs.

Post edited by: dannyh, at: 2006/05/23 21:57

Oops I double posted. See above

Post edited by: dannyh, at: 2006/05/23 21:56