1988 EL75 #1 cylinder not firing or firing intermittently

[johnstout]

I just purchased this motor 2 weeks ago. I listened to it run and it sounded pretty rough. The owner said all 3 cylinders sounded like that. Anyway, I got it home and noticed the ignition coil for the #1 cylinder was severely cracked so I replaced it. It still runs rough. I changed spark plugs still runs rough. After running for 5 to 10 minutes I pulled the spark plugs out and the #1 cylinder plug was very wet and lightly charred compared to the other plugs. Its clear that it is not firing most of the time. I wanted to check the next cheapest part out which is the coil assembly which has the pulsar coils. followed the instructions in the manual on how to check the resistance on the pulsar coils and can not get readings on any of them. Can anyone help me out here?

[Solarman]

first off, it might be easiest to hook up a timing light to each plug wire to visually see if each plug is firing equally. The light should flash the same for each plug. If they are not, then we go from there. If they are flashing the same, then it could be related to fuel, or vacuum.

If vacuum related visually inspect reed valves?

Your problem could be carb related? All air mixture screws should be set by the manual for that motor?

Post back when able to let us know what you find out.

Good luck.

[johnstout]

I'll go the extra step. I have had the motor running pulling one plug wire at a time. Pulling the top (#1) plug wire has no effect on how the motor runs. Pulling either one of the other two does. One question, I haven't used a timing light in 25 years and then only on car engines. Where do I hook up the timing light to perform the test that you asked for?

[Solarman]

Each plug wire you connect the timing light to.
What you're looking for is if each plug flashes the light the same. If all flash the same, then it is not electrically a problem.

If #1 does not flash the same then start with a plug from a good cylinder. Then backtrack from there, swap one of the good coils, making sure the wires to the coils are good as you go.

Good luck. Post back how its going when able to let us know.

[johnstout]

Okay, I had to go buy a new timing light. My 40 year old one finally gave up the ghost. I have the same light at all 3 plugs. Swapped coils around, spark plugs around and the problem stays with the top (#1) cylinder. I need to do some more reading in the manual to check the reeds and fuel issues out. I'm sure I'll be back.

[Solarman]

If you have the same flashing at all 3 plugs, then all 3 cylinders are firing the same. Don't need to change anything electrical.

Focus on gas/ fuel problems.

All three carb air mixture screws need to be set the same (by the manual).

Post back when able.

[johnstout]

Okay, I have checked all fuel lines, fuel pump is pumping okay and adjusted all the idle screws to the same position. Now my motor is idling at almost 1200 rpm and I can not find an idle adjustment anywhere. I was just reading the manual to find out how to adjust idle speed.
Even though it is running better than it was it still seems awful rough. For a lack of better words it coughs an awful lot. Could it be timing? The manual I'm looking at online says 1 5/8 turns open on the idle screws.

[Solarman]

I'm thinking all the air mixture screws should be 1.5 turns. If your motor is still coughing alot then adjust to 1.25 turns.

If still a problem coughing at idle, then the carbs should probably be cleaned, and all air pas-sages blown out with a compressed air nozzle.

There should be 1 idle stop screw located on the throttle linkage that should adjust the idle down a little.

The timing is all related to rpm, gear counting coil (distance to flywheel is important), TPS, and the pulse coils, and the CDI/ECU. The only adjustments for any of these is distance to flywheel for gear counting coil, and pulse coils. If you haven't messed with these positions, don't start now.

The TPS should be ok at idle, but would act bad when throttling up and down missing in areas, not changing timing when rpms change.

Post back when able to let us know how it's going.
Good luck.

[johnstout]

Good morning. I agree. My plan for the day is to take the carburetors off and do just exactly what you said. I'll let you know how it all works out. Thanks for the help so far.

[Solarman]

When you take them apart, do each carb separately, do not mix up any of the mixture screws, or jets between carbs (some carbs from factory had different screws to balance cylinders running on earlier models.).

Make sure you use air compressor, or compressed air can to blow through all fuel & air pas-sage ways, and jets.

If you find any trash in carbs try to identify what it is, it might lead you to something needing replacing. Black sooty residue indicates ethynol fuel breaking down fuel lines, meaning they should be replaced.

Good luck. Post back how its going when able to let us know.

[johnstout]

Okay, I removed all three carbs, disassembled, blew out all passages reassembled and installed back on the motor. I found no debris of any kind in any of the carburetors. The only thing I found was the top carburetor did not appear to have a good seal to the manifold. I then ran the engine and it does seem to run a little better but still seems rough. I intend to go after the fuel pump, strainer and lines from the tank to all the carbs today.

Let me ask a question. I really have no idea how this motor should sound running out of the water. Am I being anal about this? I know its not going to be as smooth as a singer sewing machine, but!

Okay, I disassembled the fuel pump and it is fine. Diaphragms are in good shape and no debris. Strainer was removed and disassembled and no debris found. All lines were blown out and no debris or obstructions were found. The only thing I found today was the #3 spark plug boot had a split in it. Bought three new spark plug boots and connectors and installed.

The only thing that I have done to make any change on how this motor runs is by opening up the idle screw more. The more I open them the better the engine runs. At 1 5/8's open the engine runs rough and smokes a lot. The more I open them the better the engine runs and the less it smokes and the higher the rpm's. However, the throttle plates are still closed so there is no way to turn the rpm's down. I currently have them open about 2 1/4 turns. At that setting the engine runs at about 1100 rpm's. Hope this information is helpful.

[Solarman]

If you are opening the air mixture screws that far, you may still have some blockage in the air pas-sages. The more you open the air mixture screws the more air you are mixing with the fuel at idle. The Suzuki manual tells you what the air mixture screw should be set at. If you have to vary/ change that setting more than 1/8 to 1/4 turn, then this indicates there is a blockage in the air, or fuel pas-sages for that carb. Also, if your base carb gasket is leaking air it will cause problems with mixture screw adjustment.

On the top of each carb is a screw (#4 in the parts page listing), just in line at the end of the mixture screw. Did you remove these 3 screws and blow out those pas-sages? This is your main air pas-sage for each carb.

Your throttle plates (butterflies) should be closed at idle, this is why those air pas-sages are important.

Post back when able to let us know how it's going. Good luck.

[johnstout]

Yes I did remove those screws and made sure they were open. That screw has three holes in it. 2 holes on the side of the shaft and one on the bottom of the shaft. I was able to blow carburetor cleaner and air thru the holes as well as the opening for the idle adjustment screw.

[Solarman]

What you're calling idle adjustment screw (#6 in parts listing), if it is the one front and top of carb throat, is the idle air-mixture screw. The farther you open it, the more air mixes with the factory preset/ predetermined amount of fuel at idle. This causes that cylinder to run "leaner". If you close that screw, this reduces the air mixture at idle causing that cylinder to run "richer" (less air mixture).

If you set the mixture too "lean" and run the motor for enough time, this can burn/overheat the piston causing a hole in that piston. It is better to run a slightly "richer" mixture than a "lean" mixture because of the damages it can cause.

The manual should give the best setting for all carbs, and as i mentioned in previous post, too far outside of the book recommendations indicates something is not right.

When you removed the carbs did you look at reed valves inside, behind carbs?

Post back when able to let us know how it's going. Good luck.

[johnstout]

I did look at the reed valves and as far as I can tell they look okay. I took all three carbs off again and have clear passages for both air and fuel. I reinstalled all three carbs and used Permatex high contact gasket sealer to insure I have no air leaks at the carburetor to intake manifold leaks. The product data says it has a 24 hr cure time so I can't start it up until tomorrow.
After all the testing that I have done and all the parts that I have replaced when I remove the spark plugs the #1 plug clearly is not firing like the other two.

I would like to know how to test the pulser coils. The manual says to remove the battery negative cable and to perform a resistance check. When I do this, I get no readings on any of the coils. Something is wrong with what they are telling me to do. I really don't trust the manual that much. Case in point in the tune up section it tells me that the idle adjustment is 1 7/5 to 2.25 turns. In a supplemental it tells me its 1 5/8 turns.

Even though the timing light tells me I'm getting fire to all three cylinders it doesn't tell me I'm getting enough.

Everything that I have done the top cylinder is not firing like the other two.