I know this is four years too late but for those who have just found this thread because they’re in a similar spot here’s what I’ve found:
Resurrecting a survivor H35 Tecumseh on a ‘71 MTD Trail Flite, I went through the diaphragm carb multiple times chasing a couple of problems . Like you, I have never needed to pull the Welch plugs on other carbs. Research showed there should be a check ball under the one plug and I could not hear it rattle. I knew the 40-year-old minibike had low hours and had been sitting for maybe decades and I had blown out every passage multiple times with carb cleaner and compressed air. I bit the bullet and drilled a small hole a little ways from the edge of the Welsh plug and pried it out with a small screwdriver. Sure enough, just like in your picture there was a small hole that I could maybe see a captured check ball inside of. Today’s wimpy carb cleaners were not up to the task of unsticking that ball. Multiple applications of drops of lacquer thinner got it loose and moving it around with a toothpick finally got it clean enough where it can finally seal and the thing runs great.
I found two other pitfalls on those carbs that in the old days would have been pointed out on the instruction sheet that used to come with the rebuild kits:
- I was putting in the viton rubber needle seat in the wrong way ( Square edge goes towards needle ), which caused excessively Rich running and Flooding and fuel dripping when stopped.
- If your carb is NOT stamped “F” on the mounting flange, the diaphragm goes directly next to the body of the carb and then the gasket and then the cover. If it is stamped “F”, then the order of the diaphragm and gasket are reversed, so it goes carb body, gasket, diaphragm and then the cover.
I’m not sure what fell out of your carb, but there was nothing that could fall out from under that plug on mine. The check ball is trapped up in there on mine.
