chaiinsaw mag, ohms reading, John T or anybody?

Mike(NEOhio)

Well-known Member
Location
Newbury, Ohio
I'm trying to correct a no spark condition on an old saw. Gatting 1.3 ohms on the primary on the 200 scale. No readings on the primary on 200 and 2000 scales but 20K and higher scales show 7.04. I'm not sure how to interpret that scale. Is that 7000 or 70,000? I'm a little confused.
 
I'm a little confused.

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No low voltage ohmmeter, that I'm aware of, can measure insulation breakdown.

Get another Ignition module or coil.
 
7000 would be OK as a number, I think it reflects what part of 20K it found, not a multiplier. If you put a 100 ohm resistor on the 200 scale it would read 100. Remove all rust from the flywheel magnet with 250 grit paper. Use a business card thickness .007 to .010 to space the mag to the Flywheel. If it has points make sure they are clean and set to the correct gap. If no points, and still no spark, the electronic components in the mag that trigger the spark are likely bad.
 
Mike, check the wire from your shutoff switch back to the ignition module/coil. Its very easy for this wire to find a way to short to the case, and that's how the switch shuts off the saw. A quick check is to disconnect the switch first, so its not grounding out the circuit unintentionally. Then check the wire. Then follow the rest of the advice from the others. steve
 
Thanks for the tips. Problem was the saw would start easy run fine but would die once it got up to speed. If I got off the trigger before it died it would idle good and rev again and die. I was never sure if it was ignition or carb. I haven't used it for a long time since I have other saws. The carb was clean but this time I removed the welch plugs and found a dirty screen in the high speed passage and put a kit in it. I converted to a breakerless back when it first acted up but that didn't change anything. The coil core is riveted so no gap adjustment. I'm going back to the points and try that but I'm thinking coil at this point, breaking down at high speeds. Have to get some connectors for the primary and switch wires.
 
It sounds like you are running short of gas. Check the fuel filter for free flow, and the gas line for leaks, if you got the carb cleaned good and put in a new set of gaskets/pump. What saw are you working on? steve
 
(quoted from post at 21:31:47 01/20/22) Thanks for the tips. Problem was the saw would start easy run fine but would die once it got up to speed. If I got off the trigger before it died it would idle good and rev again and die. I was never sure if it was ignition or carb. I haven't used it for a long time since I have other saws. The carb was clean but this time I removed the welch plugs and found a dirty screen in the high speed passage and put a kit in it. I converted to a breakerless back when it first acted up but that didn't change anything. The coil core is riveted so no gap adjustment. I'm going back to the points and try that but I'm thinking coil at this point, breaking down at high speeds. Have to get some connectors for the primary and switch wires.


What saw? Sounds like a fuel issue, could be related to crank seals too.
 
I have absolutely NOOOOOO info on your coil, however a TYPICAL may have very low primary ohms (maybe 1/2 to 2 or 3) AND VERY HIGH HV SECONDARY (maybe 5000 to 10000 or more ohms.)

A low energy low voltage ohm meter can tell if a coil is definitely BAD (open circuit) HOWEVER it can NOT tell you if its bad as many fail ONLY under actual HV and heat when HV breakdown occurs !!!!!!!!!!!!

Check wiring and any kill/grounding switch circuit

John T
 
Thank John. I got 1.4 on the primary and 7000 on the secondary. Worked on it more today. Put the old points and condenser back in and got a nice blue spark. Took it outside to start it. It popped twice then it was dead and nothing with ether. To durn cold to do more.
 
You're welcome, those resistances sound reasonable but as I noted HOWEVER they can show the correct ohms but often still suffer high voltage breakdown under actual HV and temp conditions......Many new condensors are bad grrrrrrrrr the old one may be better lol Insure theres no kill/grounding wires or kill switches shorted........

John T
 

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