When you say "holding down the choke button" do you mean the primer bulb? I read where a guy was having similar problems and did the same thing to aleviate the situation. He eventually got fed up and tore down the carb to find that it was partially gummed up. It may just need a good cleaning with a can of gum-out and a gasket set. Have you stored it properly over the years?

Yes.. I mean the primer bulb. I got the lawn mower as a hand-me-down two years ago. Last year it was doing the same thing at the end of the year. I would need to hold the primer bulb down for a couple of seconds and then it would run. If possible, can you explain what this can of gum out is?? Do I get it from sears or home depot? Is made for lawn mowers specifically? Thanks for your reply, I appreciate all your help.

I did not do anything special with the lawn mower over the winter. (Hey.. at least I am honest!) I changed the spark plug last year and I know for sure the gas is not old.

I am an electrical engineer and I do some work on cars, so I feel like I want to TRY to fix this before I take it in. I just don't know where to start.

You need the float bowl kit
Tecumseh PN 730637A
Don't mess around trying to "fix" the carb.

Gum-Out is a name brand of aerosol carb cleaner and you can get it at any auto parts store. It's for any carburetor, not specifically automobiles or lawn mowers etc..

The gas in it now may not be old, though many will argue that gas more than 90 days old, or less!, shouldn't be used. The gum would have been deposited from improper storage and care from the time before you got it and wouldn't have been helped by the fact that it wasn't run dry or a fuel stabilizer added by yourself before storing last winter. No offense intended.

At any rate, I'd do like bill_kapaun suggests and get the float bowl kit and a can of gum-out(it will help clean it up after it's apart and before re-assembly). Pipe cleaners are handy for cleaning out carbs too. Have fun with it!

After a couple of months of disuse, my three year old Eager-1 Tecumseh would only run on start spray. After draining the old fuel (and recycling in the truck) I turned the mower on its side and unscrewed the float bowl screw then reamed the side holes with a tooth pick and the smaller ones in the upper side and in the center with a twist-tie wire. Reinstalled the screw, new gas and shazam, it started and ran like new. Might need to fix something else later but this is an easy thing to check first.

Well, I'm going to refresh the gas and try again.
I'm no slouch with the tools, and already used carb cleaner, wire, and some compressed air to clean the carb out.

I would be surprised if I need to spend $30 on a whole carb kit. The float, needle & seat are fine, all gaskets are good, and the extra primer bulb would be a waste. The mess I was seeing in the needle-jet looked to be old rubber, and not the normal varnish/dirt that you get from bad gas.

If anyone could show me a proper exploded view of this carb, I'd be a happy camper. I have a sneaking suspicion that someone put an O-ring up in there at some point.

Oh, and no worries about preparing this one for winter or storage etc.... I got this one off a farm where it sat in the pumphouse for a couple years unused... Not my fault, so no offense taken.

Fuel left in fuel lines, carb, etc, for a few years or more can "gel" which looks and feels like rubber.
Also, in an old lawnmower I was recently given, the pump diaphram was actually delaminating, and pieces of rubber from it were melting in the fuel and getting stuck in the small passages and valves.

Mostly the tiny holes in the carb gum-out by gas "gel". I opened the bottom of the carb use can-air with red tube aimed on those holes and blow it. I feel this mower can run forever now.

One more thing is check the spring of throttle governor. It could be over stretched and make the throttle remained in close position.