MTD Briggs No Spark

[Texas Denny]

I have a MTD lawn tractor with a model 42A707 Briggs horizontally opposed 2 cylinder. I backed it out of the shed, had it running and it quit. It wouldn't start again. Checked the plugs and get no spark. I found a yellow wire that runs from the coil to the ignition switch. When the switch is on, the resistance is infinity to ground. When the switch is off, the resistance to ground is zero. I am assuming that the yellow wire is the kill wire. I can find no other wires running from this coil assembly. The magnets are very strong. On some Briggs engines there was a set of points and a condenser under the flywheel. Does this one have those parts?

One other piece of info is that the spark got weak as the engine is warmed up. It could not be started during use - it had to cool for up to two hours.

I'm wondering if the coil is bad? Or are there other parts I haven't found. I don't have the flywheel off. I will pull it if it will help solve the problem.

I've done lots of work on farm tractors but have steered away from the air cooled variety in the past.

 

[El Toro]

It's probably the coil. You will need the model number off the engine and you may the engine type too. Your local lawnmower repair shop may be able to test it. I think they've had problems with the coil on these engines. Hal

 

[IH2444]

btw I don't think it has points under the flywheel.
Just the coil.

 

[Kentb of SWMO]

Magnetron coil, NO POINTS OR CONDENSER, will just die. Replace and the engine will be running. Costs around $40.00.

Kent

 

[Texas Denny]

Thanks ElToro, IH2444 and Kenth. This analysis seems very logical. I'd felt this part (or parts) were on the way out for some time. Inability to start a warm engine is a warning sign to me. I've ordered the new part from Briggs.

When I receive the part, will it give me the correct gap to the magnets. Or do any of you know what it is? Thanks,

 

[rustyj]

When setting the coil to flywheel gap, i use a business card, or a slice of birthday card. cut a piece about 7 inches long by two wide. After you getthe new coil attached, pull it out away from the flywheel, and snug up the bolts.
Then, turn the flywheel until the magnets on it are evenly aligned with the coil legs. Place the strip between the coil legs and the fywheel magnets. Loosen the bolts and let the magnets pull the legs in against the paper strip. Do not push on it!! Tighten the bolts, turn the flywheel and let the strip slide out. This will give the correct gap for the coil to flywheel area.

 

[Texas Denny]

Thanks,

 

[Kentb of SWMO]

For the flywheel gap I use one of the flaps on the box that the coil comes in.

Kent

 

[Bob - MI]

Check to see if a mouse git in and chewed through any wires. Had that more than once.