Tec AV520 no spark

[jleb]

I have an 80's AV520 670-05F 3hp 2cycle vertical shaft engine that does not have spark.
I have replaced the coil, condenser, and points. The kill switch is good and actually not connected at the moment. The points and plug are gapped correctly, the flywheel magnets are good, the air gap is fixed on this model, I can feel the spark when holding the plug wire and spinning the flywheel by hand but when i insert the plug in the wire and ground to the engine there is nothing. I am completely stumped why I'm not getting spark. I have another same motor that gets the exact same meter readings at every point I check and gets great spark when tested by hand.
It is acting like the kills switch is connected and off even though it is not. Is there anything that could be grounding causing this no spark issue?

 

[Hammermechanicman]

"I can feel the spark when holding the plug wire and spinning the flywheel by hand"

Sounds like the points are slightly out of time with the magnets. Try opening the points gsp a couple thou. If that doesn't help then close a couple thou.

 

[Rivets]

Sounds to me like your timing is not correct. This will happen if you removed the magneto assembly. Timing these ignition systems is not easy unless you have the proper dial indicator. It can be done without the indicator if you have experience in how the indicator is doing its job, but does take time and a good vernier caliper. Here is a manual which tells you how to set timing. https://www.mymowerparts.com/pdf/Te...HSK600-TVS600-Craftsman-200-Series-692508.pdf

 

[jleb]

Sounds to me like your timing is not correct. This will happen if you removed the magneto assembly. Timing these ignition systems is not easy unless you have the proper dial indicator. It can be done without the indicator if you have experience in how the indicator is doing its job, but does take time and a good vernier caliper. Here is a manual which tells you how to set timing. https://www.mymowerparts.com/pdf/Te...HSK600-TVS600-Craftsman-200-Series-692508.pdf

This model has a keyed cam for the timing. The key has not sheared so the timing should still be good. I have read through this manual and checked every position and gap for this motor and everything is correct. When I hold the plug wire and spin the flywheel, I can feel the spark at both points (wire and flywheel) but I get nothing from plug to motor which makes me think something became grounded, I just cant find where.

 

[Rivets]

Sorry, but you are wrong. The cam may be keyed, but the timing is adjusted by moving the magneto assembly. Trust me, I grew up with these engines.

 

[jleb]

Sorry, but you are wrong. The cam may be keyed, but the timing is adjusted by moving the magneto assembly. Trust me, I grew up with these engines.

Fair enough. I will go back and re read and double check everything. But if the timing is off, wouldn't I still get spark, just at the wrong time?

 

[Rivets]

Not going to get into an argument how the old Tecumseh ignition systems work. Bye.

 

[Hammermechanicman]

If the magneto assy wasn't moved that's good. Moving the mag/coil assy adjusts the engine timing but the points gap is critical to timing the magnets to the coil.

 

[Rivets]

You are assuming that the old points gap was the same as what the new points gap is set at. We’re talking thousands of an inch which is very critical. I’ve seen Tecumseh engines run at point gaps ranging from .016“-.022”, depending on how the timing was set. Also, your condenser may be bad, which will also affect spark strength. I still test condensers today when ever working on these systems. Don’t need special equipment if you’re not afraid of getting shocked once in awhile. Here in Wisconsin we still have a lot of the old mule SnowKing engines being used.

 

[jleb]

Not going to get into an argument how the old Tecumseh ignition systems work. Bye.

wasn't trying to argue. you are correct about timing being off. I'm not a motor guy. was just asking a question