Garden Tractor clutch kills engine

I just got a used MTD/Ward garden tractor at an auction. It has an 18hp Briggs engine. It's probably about 14 years old. In order to start it, I have to push down the clutch. That's normal. But when I let up on the clutch pedal, the engine dies. No, it's not a tight belt. It's in neutral and the belt is fine. The mower deck is off, so that's not the problem. It basically loses electric power to the engine ignition. I know that because if I push the clutch down, the muffler pops. The same thing a car engine does if you shut off the ignition and then turn it back on.
That switch on the clutch is supposed to be for safety when starting, but it's supposed to stay running once started. Although I am familiar with electrical wiring, I am having trouble understanding how this works. Does anyone have any ideas what is going on?
PS. There are no contact switches under the seat.
Maybe I will just have to eliminate that switch and wire it direct to the ign switch. But I thought I'd ask on here first.
Thanks LM
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snipped-for-privacy@invalid.com wrote:

Don't know that one particularly (you should be able to finds a parts diagram online somewhere I'd think), but there's a couple of ways.
Either there's a centrifigul relay or one on the generator coil that's not working or the one on the clutch has a secondary coil that isn't.
Trace the wiring if you can't find a diagram; if you can't find the other relay, then it's combined in the one.
--
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Check if there is supposed to be a safety switch on the deck or shift mechanism. Some riders are interlocked so that you can not back up with the blade running. There is usually a seat switch also to prevent getting off of the mower with it in gear or the blade running.
Don Young
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