Is it my ignition coils?

Hi everyone, this is my first post here and I'm pretty inexperienced with motorcycle repair.

I have a 1980 KZ750 E1 that I bought about two weeks ago. It ran rough when I bought it, and the guy I got it from told me it just needed a good carb cleaning.

I took the carbs out and they looked really clean. The jets were a little clogged, so I sprayed some carb cleaner and compressed air through them. The screwdriver slot in the jets, the primary ones I believe, were partially stripped, so I didn't take the jets out.

The bike ran better, but still backfired occasionally and never had full power, so last weekend I checked the spark plugs and the 1 & 4 plugs were all blackened, but the 2 & 3 plugs were perfect.

My best guess right now is that there is something wrong with the coil for the 1 & 4 coils, but I don't know how to test them, which ones to get as replacements if it is the coils, if I need to replace both coils or just the one that isn't firing, etc.

Thanks for any help you can provide. (sorry, no pics yet)

Chris

I'd replace the sparkplug caps(they screw onto the sparkplug wires) first, then the sparkplug wires later.

Remove the gas tank, and look at the primary(small wires) side of the ignition coils for tightness. Some Kawasaki's have 1/4" wide male electrical connectors that require the matching female connector.

Over time,heat,and vibration can work them loose.If they are loose, take a pair of needle nose pliers after the treminal is removed from the coil and carefully squeeze the area that grips the matching terminal on the coil and re-install it.

Welcome to the forum, Chris.

First thing I would do is get a manual for your bike. Looks like your luck is good because here is a link to a free manual download for your KZ750E:http://kz.mbsween.com/manual.html

If you need to test your coils the manual should provide you with the proper procedure and specs under the ignition section. You'll have to buy a cheap multimeter, you can usually find them for under $10 (I got mine at Harbor Freight for $2.99 on sale). But first I'd pull all the plugs and put them in the plug wires and hold the ends (one at a time) against the motor case (be sure to hold the wire and not the plug or you'll get shocked) just to verify that you're getting spark at 1&4. Buying new plugs wouldn't hurt also, it's cheap insurance. If the spark appears weak and the caps look ok, you can often create a better connection between wire & cap by twisting the caps off (assuming you have removable caps, most coil wires do) and very carefully snipping about 1/4" off the end of the insulation without cutting through the metal wire, then replacing by twisting the cap firmly back on (until it stops turning). This gives the coil wire a better lead, and hence a better connection to the cap. When you start it back up, check how hot the 1&4 cyl headpipes are by throwing a little water on 'em. If they sizzle and steam that means they're firing pretty good and it might be running rich because the air/fuel mixture is rich. Or if you're really brave you can touch 'em with your hand to check the temp, but be quick about it or else you can get burned. If the pipes are hot, the next step would be to adjust the air screws on the 1&4 cyl carbs. Turning the screws in enriches the mixture, turning them out leans the mixture.

If none of this helps, you may want to check your compression as well. A compression test will give you a good indication of the overall state of your engine, is easy to do, and is a good thing to do. Compression testers can be had cheap, I got mine for $7.99 (again, on sale at Harbor Freight). My troubleshooting method is to rule out the more basic problems first, and if none of those tests provides an answer, I work my way progressively towards the more complicated.

And here's a link to an awesome FREE site that teaches you how to work on motorcycles (lots of great tips here):http://www.dansmc.com/mc_repaircourse.htm


Hope you get 'er running good.

Thanks for the advice. I'm going to start checking the caps, wires and coils tonight. I'm pretty sure the primary wires have a decent connection to the coils' male connectors.

When I test to see if I'm getting spark by holding the plug against the motor case, should all of the other plugs be installed and connected, and should the motor be running? Will it run with only three plugs installed?

No, you don't want the motor running when you check for spark. Pull all the plugs, put them in the caps, and lay them on the engine. Now hold each plug's electrode one at a time against the motor (a bolt makes a good ground), turn the motor over, and check for spark. Sometimes it helps to have some shade over the plug to see it better. Or you can buy an inexpensive spark checker at the auto parts store. You can also check to see how much voltage you're getting to the coil(s) by setting your multimeter to the proper dc voltage setting (the first setting above 12, on mine it is 20), turning the key to on (or you could test while the motor's running, probably better) and touch the red (+) probe to the red power wire where it attaches to the coil, and touch the black(-) probe to ground. If your getting anything less than 12 volts then you may want to test the coil's primary and secondary windings with your multimeter following the instructions in the manual. If the coils test good, then you might want to do the WG coil mod to increase power to the coils. Here is a link that shows you how it's done:http://www.wgcarbs.com/index.php?option=com_content&task=view&id=12&Itemid=26\

Hope this helps. Best of luck! Post some pictures of your ride when you can.

Well, I changed the coils using some 2.2ohm Dyna Coils from another KZ750 and it was 100 percent better ... until I tried to drive it. The engine sounded great while parked in neutral, the knocking sound from inside the 1 & 4 cylinders was gone, all the pipes were hot and I was so excited to get the bike on the road!

Almost immediately after I put it in gear, though, it started bogging down. It barely made it up a pretty small hill and the knocking sound returned. The 1, 2 & 3 pipes were hot, but the #4 pipe was barely warm.

I'm going to go through the carbs again and see if that helps. I noticed that I forgot to put one of the plastic plugs back in when I cleaned them last time, but I don't know if that could be making the difference.

Man what a letdown! :ohmy: I'm sorry to hear it's not going so well. Really odd what you describe, did you rev it up some while the bike was parked in neutral and it seemed to be running great? Are you sure the dyna coils will work with the rest of your ignition system? Did you check your voltage at the coils? You could have bad wiring and it's not providing enough juice to the coils. In that case you may want to do the WG coil mod. Does it run good at idle and/or low RPM only to crap out at higher RPM?

If it craps out when you rev it up, then check the spark advancer.It's located on the right side of the engine case underneath the small round cover held on with two screws and it should have the Kawasaki logo on it. Have a look at the attached photos in the next 2 posts. This is what you should see.
Next you'll need to remove the copper colored plate that holds the igniter coils. Remove the 3 igniter plate screws. Remove the igniter plate. Disconnect the oil sensor wire, I think it's the blue wire with the red stripe that attaches to the little metal cylinder on the bottom of the case. Now you need a narrow width 17mm wrench (the one in my KZ650 tool kit works perfect) and a 13mm wrench to remove the bolt that holds the spark advancer on the crank. The 17mm wrench keeps the crank from turning while you loosen the bolt with the other wrench. If you don't have the right 17mm wrench you can put the motor in first gear and step on the rear brake to keep the motor from turning while you loosen with the 13mm wrench. Now you should be looking at the spark advancer. You should be able to pry it off with a screwdriver. Once it's off the motor, try rotating the cam (oval thing in the center of the unit on spindle)to the right as far as it will go (it should be about 1/2") and let go. the springs should snap it back to it's original position. If it's frozen or the movement is "sticky" you need to soak it in Liquid Wrench or some other penetrating oil so that it moves smoothly and quickly. If it's too far gone you'll need to replace it. Hit me up, I have a spare one that came off my 650 that should be identical to yours.

Be sure the gas tank and fuel petcock is clean and that you have fresh gas. If the bike has been sitting for any length of time you'll need to clean the entire fuel system, I always install an inline fuel filter just to be sure.That knocking sound is a VERY bad sign, and could be an indication that you may need major engine work, and is the first time that you have mentioned it. Something tells me your bike has more wrong with it than just fuel issues. Hope I'm wrong about this, but that "knocking" sound could be a bad piston rod. Have you changed the oil yet? If not, now would be a good time to drain the oil and check for metal shavings in the oil and/or the oil pan. If you find metal, then you've got serious problems. I would also run a compression check as well to rule out any top end issues. If 3 of the pipes are hot, and #4 is just warm, it would seem like you're firing on at least 3 cylinders, say 3 and a 1/2, and that even if the missing plastic plug (goes on top of the pilot jet?)is causing #4 not to fully fire, logic tells me that it should be running better than you describe.


After I cleaned the carbs on my KZ650 I didn't tighten down the pilot jet on my #4 carb enough, and this caused too much fuel to flow to the piston, and unburned gas was dripping out the exhaust port of the #4 cylinder down the exhaust pipe, which was only warm. Despite firing on only 3 1/2 cylinders, the bike ran surprisingly well, it would hit 10,500 RPM, didn't ping or backfire, and I was able to get it to 80 MPH, but it just seemed pretty sluggish. When I pulled the float bowl off carb #4 the dang pilot jet fell out. Screwed it back in good and tight and I was firing on all 4 and life was good. But even with the bike running on 3 1/2 it was still pretty smooth. And it didn't make any ominous knocking sounds. So something tells me there's more going on with your bike than just a missing carb part.

I'm curious about the knocking sound. Does the bike backfire and ping any? Smoke? Is the throttle response rough and stumbly?

Another thought: maybe it's a tranny problem? Does it run good in neutral? Are your brakes dragging?

Keep me posted, I'm here to help if I can. And If I can't, I'm sure there's someone here who can.
Good luck.

Here is the picture of igniter plate.

Here is a picture of the spark advancer.

Thanks a ton for the advice. I'll check out the spark advancer tonight. The bike was sitting for a while, not sure exactly how long, but the carbs actually looked pretty clean when I took them apart, so I'm guessing it wasn't more than a year. The tank is a little rusty inside, and I plan on sealing that up, but I didn't think that it would be that big of a problem for the short term.

The Dyna coils are the 2.2 ohm, and the manual said they should be between 1.8 & 2.8, so I think those are the right ones. I'm going to do the coil mod this weekend anyway, so hopefully that helps a little.

I first installed one of the dyna coils on the 1&4 cylinders just to see if maybe that was my problem. The bike started up instantly, whereas it usually cranked over a couple times before starting. It sounded perfect and there was great engine response when I turned the throttle. I also noticed that the smoke that usually came from the exhaust was no longer there (usually a bluish color).

Previous to these last issues I've been having, the engine backfired pretty regularly and it would suddenly accelerate very quickly without any change in throttle, as though it were only firing on two cylinders and then all of a sudden all four kicked in.

I'm going to reclean the carbs tonight and get the coil mod done and check the spark advancer tomorrow. Hopefully that should narrow it down a little more. I'll be really bummed if it's a major problem - this is the first bike I've owned in two years and all I want to do is ride!!!

I've been sitting back reading the topic wondering if I might find an answer to a problem that's been bugging me.
I think I have the answer in the coil power mod!!! It seems that the bike will run great on all fours, then once in a while, at idle, it seems to loose a cylinder & start to backfire and won't idle worth (you know).. At the next red light, it'll be fine again
i don't want to steal the thread... Just thanks for the info..

Glad to hear the coil mod worked for you parmakz. Apparently that's a good solution for a great deal of vintage motorcycle owners.