Same thing is happening to my china built engine. I may look at the carb again

When the engine quits, can you immediately restart? Try checking the ignition system for spark immediately after the engine quits. This would tell you if the problem is ignition or fuel. The switch actuated by the compliance cable may be right on the edge and may be grounding the ignition.

I've ruled out ignition as I can keep the engine running by squirting some starting fluid in the carb intake just as the engine begins to quit. To recap the problem, the engine starts easily with full choke but needs almost full choke to continue to run. But after 1 to 2 minutes, the engine stops and backfires at the last few revolutions. This would seem to indicate leaning out which suggests that the carb fuel bowl is running dry. If I wait a couple of minutes, the engine starts easily but quits every time after a minute or so. My guess is the the float needle valve is sticking closed as the fuel in the bowl is being consumed. But I cannot find the reason for this after several total carb teardowns. The needle valve has a rubber tip but it looks OK. I've found that buying a new carb is not much more expensive then buying a needle valve which is $20.

Any other suggestions would be most welcome.

Thanks, Ray

Ray,

Have you tried running it with the gas cap off?

Also, while there may be no reason to believe that the float level setting has changed, did you check it?

Jim

Jim,

Per your good suggestion I've tried to run the mower with gas cap removed but it made no difference; still qiuts after 30 or so seconds. The gas cap vent was clear. I think that you are correct about the float level but there is no adjustment possible as the float is plastic as is the arm that moves the needle valve. I plan to either buy a new carb or buy a valve/float assembly. Thanks for your help.

Ray

Ray,

It sounds like you've probably covered all the bases except for buying the new parts or a new carb, but just a couple of more thoughts to throw out.

As I said you've likely done this, but if not, have you made sure the gas tank screen is unclogged?

And this is silly perhaps, but if you could stomach taking the carb apart again without rebuilding it, and under the assumption that the float valve is sticking, you could mount the needle in an electric drill and with very fine wet/dry silicone-carbide paper (600 grit or finer maybe), gently reshape the rubber tip so that it has an ever so slightly more blunt profile. If you think about it, if the tip develops a sharper angle than the valve seat, it will tend to stick in the hole at the end of the cone shaped seat, like a cork in a bottle. But if the tip is the same shape as the seat, or slightly more blunt, the elastic forces that develop in the tip will tend to push it off the seat, rather than anchoring it there.

I've never tried this, but if you're going to buy new parts anyway, and have the time...

Jim

Jim,

I replaced the carb but problem remains. Finally and in desperation, I brought it to the dealer from whom I bought the Honda carb (only $22.00). He found that the gas was bad, no water but just bad! How embarrassing. With fresh gas the Honda runs like new. He reinstalled my original carb and refunded cost of the new one. He claims that a large share of his repair work is associated with bad fuel.

Thanks for your help,

Ray