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I have a Troybilt chipper/vac with the 5 hp H50 engine. A couple of years ago it started to stall out after a few minutes. I tried adjusting the main and idle jets but couldn’t make it work. I stuck it under my deck. Recently retired and with time on my hands took it into the sunlight and gave it another shot. The bowl was full of scale. I bought a new Chinese carb rather than even try to rehab the old one. I didn’t realize that there was water in the fuel tank. I tried to start it, priming it with a shot of starter fluid. I suspect I drew water and dirt into the new carb. So I cleaned the tank and put new hose, fuel shutoff, and filter on. I blew air through the hose back into the tank. All clear. Also cleaned carb (but did not remove welch plugs) and reset main and idle jets to specs. It started right up but went back to stalling out after a minute or two. Then it would not restart. It seemed like it just flat ran out of gas. If I let it completely cool, it would start easily again and then quit after a minute or two. I thought maybe weak coil going bad after getting hot. I replaced the coil with another fine product of China. As we said in my flying days, no joy. I even replaced the spark plug although I was pretty sure that wasn’t the problem. No joy. I am out of ideas. Could the governor be doing this? Is there something inside the carb behind the welch plugs that kicks in after warmup that is shutting the fuel flow? Any help would be appreciated.

I would suspect that the cheap carb you purchased is not a direct replacement or not set properly. I would start by pulling the new carb off and check the float level. Holding the cab upside down the float should be level or slightly down on the side opposite the pin. I like to set them slightly down, making them run alittle rich.

Is it a metal fuel tank? If tank is rusty you will have a hard time getting all the rust out. Been there too many times. Check the tank vent. Start it with the air cleaner off and when it starts to die spray some carb cleaner or starting fluid into the carb. If it runs better for a few seconds you have a fuel problem.

Rivets said:

I would suspect that the cheap carb you purchased is not a direct replacement or not set properly. I would start by pulling the new carb off and check the float level. Holding the cab upside down the float should be level or slightly down on the side opposite the pin. I like to set them slightly down, making them run alittle rich.

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Thanks. I set the float level before I installed the carb but will try your trick and set it lower. I’ve also considered using the main jet off the old carb. It is much better machined than the new one.

Hammermechanicman said:

Is it a metal fuel tank? If tank is rusty you will have a hard time getting all the rust out. Been there too many times. Check the tank vent. Start it with the air cleaner off and when it starts to die spray some carb cleaner or starting fluid into the carb. If it runs better for a few seconds you have a fuel problem.

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Thanks. It’s a plastic tank. I thought about the vent issue and tried running it with the fuel cap loose. Didn’t help. I’ll try spraying starter fluid as you suggested if Rivets’ idea doesn’t work.

If still no go, with the engine cold, turn the engine to TDC and measure the valve gaps. Too small will leave the valve open quickly as it warms up.

upupandaway said:

If still no go, with the engine cold, turn the engine to TDC and measure the valve gaps. Too small will leave the valve open quickly as it warms up.

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Great idea. Valve problem is consistent with the fact that I had the same symptoms before I got fed up and stuck it under the deck. I’ll put valve clearance check on the triage list. Thanks.

Thanks to all. The engine now starts easily and runs well. I checked the float alignment and set it slightly lower, as suggested. Didn’t help. I checked the valve clearances. They were correct. While there, cleaned some carbon off. Didn’t help. I hate to admit this, but the problem turned out to be that I didn’t put enough gas in the tank. As a general practice, I only put a small amount of fuel in any machine I am working on, especially if I plan on putting it into storage. This tank has a baffle on the bottom and although the floor of the tank was covered with fuel, it wasn’t enough to get past the baffle and to the outlet fast enough to keep the engine going. The aha moment came when I noticed that when I pulled the fuel line off the carb that the fuel was barely a trickle. I had already made sure there was no blockage. I hope this red faced confession helps someone else.

Don’t be red faced, you’re not the first nor will be the last, to forget that an engine needs an appropriate amount of fuel to run properly. Every tech on this site has pulled their arm off trying to start an engine with no fuel in the tank.

Another idea is to keep fuel tanks full. This trick provides less air for the fuel to mix with so less oxidation and the fuel stays viable longer. Buy premium as it degrades more slowly and prior to storing for a long period of time put some stabilizer in with the fuel.
By the way, just Sunday night I couldn't get an engine started. I used carb cleaner to establish it worked, but it just kept stalling out. I had just put in a little gas, as I thought I would have to turn the mower over to pull off the blade and when I did get it running it drank everything in a matter of minutes. Rivets is right. It happens to us all.