Trying to fix a Craftsman T1000 lawn tractor for my elder neighbor. He's having issues with it starting and only running for a few minutes then dieing and surging in low idle. Thinking it's a fuel issue, I decided to remove the carb and clean it. Noticed that the fuel bowl o-ring was getting dry rotted so I bought an OEM MTD o-ring to replace it. Having issues trying to get a new fuel bowl o-ring to stay in place on a MTD/Huayi 4P90F carb while I put on the fuel bowl. The grove on the carb body is bigger than the o-ring. The bowl is a cast one not stamped. Any ideas on how to keep it in place without losing the integrity of the o-ring while I put on the bowl?

The carb mounting area is slightly larger than the new O-ring, correct?
 
If so, with the carb upside down, simply stretch it over the carb body.  It's new, it'll stretch and then stay in place (put the bowl back on)..
 
There's a very, very small jet located under the idle screw adjuster.  That ALWAYS clogs and will cause surging..  Un-screw that screw, then they'll be a plastic spacer(usually). Under that you'll see another part (mostly plastic). To clean that jet I use a cut off piece of wire(from a wire brush).  My carb cleaning rods won't go that small(and they do go small).