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Old 08-10-2017, 06:53 PM
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Default 1988 EL75 #1 cylinder not firing or firing intermittently

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?
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Old 08-11-2017, 07:47 AM
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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.
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Old 08-11-2017, 10:39 AM
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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?
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Old 08-11-2017, 11:17 AM
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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.
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Old 08-11-2017, 02:04 PM
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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.
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Old 08-11-2017, 02:53 PM
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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.
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Old 08-11-2017, 08:10 PM
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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.

Last edited by johnstout; 08-11-2017 at 08:42 PM.
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Old 08-12-2017, 09:21 AM
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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.
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Old 08-12-2017, 10:46 AM
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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.
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Old 08-12-2017, 01:33 PM
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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.
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