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Discussion Starter #1 (Edited)
Hi everyone, I'm a novice at troubleshooting this old 250 4x4 Trailboss which I have had since it was new. It has generally been pretty reliable but in it's later years would be very difficult to start and sometimes it would die and very hard to restart and then it would not start at all. Recently, my son checked the compression and it was very low. He rebuilt the engine. It's back together now and we can't start it. Same story as before rebuild. I suspect an electrical issue. Have weak spark. Shot of ether directly into cylinder or directly into carb with air filter box removed and throttle open and zero response. I am cranking the unit with the electric start. Thinking it is a spark issue since Ether does nothing. I performed the following checks:

* Secondary (Ignition) Coil - Primary side- Primary Tab to Ground Tab = 3.5 ohm (recommended .3 to .5 ohm)
* Secondary (Ignition) Coil - Secondary side resistance - High Tension wire (cap removed) to Ground Tab = 5950 Ohm (recommended 6300 ohm +/- 10%
* Spark Plug cap resistance = 4700 ohm (recommended 3700 to 6300 ohm)
* Resistance of the entire Ignition coil, plug wire, plug cap assembly (ground tab to inside of plug cap) = 10690 ohm (I found no spec on this)
STATOR COIL RESISTANCE
* Exciter Coil = 99 ohm (recommended is 120 ohm +/- 10%)
* Lighting Coil = .5 ohm (recommended is .3 ohm +/- 10%)
* Checked Reverse speed limiter (black, yellow and green wires all are open to ground and white measured 630 ohm to ground
* Reverse override switch measures to be "normally closed" between green and purple wires and it opens when the button is depressed.
* The throttle safety switch is also always "closed" when I checked it
* Disconnected the black wire at the reverse speed limiter and still the same problem (I think I disconnected the correct wire. I did all 4 black wires, one at a time and rechecked each time - these wires were located in the terminal strip area to the right of the ignition coil)

Of the above numbers, some are out of spec (noted in red) but I am not sure if they are bad enough to get zero ignition. I was thinking next step is to replace the CDI module?

Any suggestions would be greatly appreciated ! I am following troubleshooting instructions from my manual. But I have no real background and not sure of the best the next step.

I greatly appreciate any help anyone would have on this problem.

Thank you!
TBwoods
 

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Did you ever figure it out? If so what did you find? Having the same issue. Rebuilt as well and no change won't even fire off ether. It has spark but seems weak.
 

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The thread is 3 years old - just start a new thread and describe the problem - before you do, get as much diagnostic info as possible. What is the compression? Is the spark plug new? Is the spark plug other than Champion? When was the engine rebuilt and what was done to it? Etc. Most weak spark problems are magneto related and the stator is the most common failure.
 

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The thread is 3 years old - just start a new thread and describe the problem - before you do, get as much diagnostic info as possible. What is the compression? Is the spark plug new? Is the spark plug other than Champion? When was the engine rebuilt and what was done to it? Etc. Most weak spark problems are magneto related and the stator is the most common failure.
Sorry will start a new thread next time, but I got it running today by making the spark plug gap very tight. NGK R plug. Might take the side cover off and check out the stator.
 
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