5HP Briggs tiller engine problem

I got a front-tined tiller off of a guy down the road this past Spring with a 5hp B&S engine on it. It ran fine, save for a few minor issues with the throttle control, but when I went to start it up this Fall, it won't do anything. Here's what the engine is: Model 130292, Type 0159-04, Code 7502-1007

Here's what I've tried so far:
- Checked jet on carb - it is clear
- replaced diaphragm on carb
- looked for crud in the carb - looks totally clean to me with no corrosion.
- checked spark plug - works fine with nice, bright spark
- dumped old gas out of the tank, rinsed with new gas, and refilled
- checked and cleaned intake filters on carb

I'm assuming this is an issue with old gas because I've only had it 8 months or so, but I don't think I ever ran it out of gas so the gas in it is probably a year old or more. The tiller itself is 40 years old, and the previous owner had it for 2 years before switching out to a rear-tined tiller. I thought dumping the gas and rinsing the tank would do it, but still no luck. Even when I put NEW gas into the spark plug hole, I'll hear it "pop" and get a little smoke out of the exhaust, but it doesn't turn over.

My next thought is to start replacing gaskets. The one between the carb and the gas tank is particularly bad, and also there is occasional smoke that comes out from the crack where the top of the engine that the spark plug sits in and the bottom of the engine are bolted together so that gasket might be bad too.

Any thoughts here? I'd like to get my garden tilled under before the ground freezes!

 

Yup. Replace the gaskets first. The head gasket (top one) can cause a lot of problems. Then stick a little Sea Foam in it and see how it does.

 

Have you ever used a front tined tiller before?
Being a front tine and being that old I for sure would not be spending a dime on it.
That thing will beat you to death.
A rear tine you can run with one hand until you have to turn.

 

In my experience with that sort of tiller and engine, there was a SIDE diaphragm on the carb... 2 screws and a cover pops off. There are a couple flaps on that diaphragm that would crud up. And even when the diaphragm was clean (or new) it seemed like if it got dry that it wouldn't prime. So maybe take that cover off, shoot it with something oily, like wd40, then put it back together and see if it primes.

If you try using starting fluid to start it, you will probably blow the head gasket. Or maybe it's been blown already.

 

If it's just popping, I would be changing the spark plug first, then if no joy, check to be sure a vale isn't hanging open. It could even have a sheared flywheel key. I never had starting fluid cause any problem with a head gasket, but I never really use it anyway.