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Thread: Help with ohm meter readings on my 86 Big Red.

  1. #1
    MN250R's Avatar
    MN250R is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Help with ohm meter readings on my 86 Big Red.

    Hello, i been chasing down and engine problem My 86 big red would start to sputter if you give it more than 1/8 th throttle. Machine runs awesome for like 20-30 mins. Only happens after it gets hot.If I shut it off and let it cool down, it runs fine again for the same amount of time. Sounds like the spark is cutting out and its pinging. Feels like the machine is jerking when it starts acting up. Fresh gas and no vapor lock as I tried two different gas caps.
    Here are the readings I got from measuring the ohms.
    Can someone explain how to read these. Ignition coil says .18 +- 0.018. Does that mean it should be .18? What is the other number for? I got 1.3 with old coil and 1.4 with the new one. Resistance on secondary coil says 9.1. +- 1.66. Old coil was 11.7. And my new coil says 2.03.

    Any help would be great explaining if it's better to have more or less resistance.
    1986 ATC 350X
    1986 ATC Big Red 250ES

  2. #2
    MN250R's Avatar
    MN250R is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Here are my readings. Thx!

    Sent from my SM-G960U using Tapatalk
    1986 ATC 350X
    1986 ATC Big Red 250ES

  3. #3
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    Let's use the ignition coil as an example. If everything inside the coil is perfect and the air temperature is right at whatever they call for, then you should get a reading of .18. You can vary from the .18 by .018 either high or low. That means that the acceptable range is from .162 to .198. They give you a "room temperature" of around 65 or 70 degrees to test at to get the same readings that they do. if the temperature's higher, you will have a slightly higher ohms reading, while it will be slightly lower in colder weather. It appears that neither ignition coil is in spec on the primary side. The old coil is in spec on the secondary side while the new one isn't. Of course if it isn't in spec one one, then it should be replaced. Did you buy a Honda coil? They are the best way to go. The exciter coil and the pulse generator are both fine. You may right about the spark "cutting out". It could be that as the coil heats up, it builds up enough resistance that it no longer makes spark or doesn't make a hot enough spark to light the gas in the cylinder.

  4. #4
    MN250R's Avatar
    MN250R is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Thanks for the reply! That makes sense now after u explained it. Weird that the new Ebay coil is off on the numbers. It started right up. I will be giving it a test run tommorow with the new coil. I also noticed tonight the sparkplug was built up with black carbon. I cleaned it. I will also be getting a new spark plug to try.

    Sent from my SM-G960U using Tapatalk
    1986 ATC 350X
    1986 ATC Big Red 250ES

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