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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 28654
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I had a similar issue that engine will only run when choke

Customer Question

I had a similar issue that engine will only run when choke is fully closed. Here's a hint, the guy I bought it from said he cleaned the carb, when I picked it up from him he handed me a sandwich bag with 2 small, 1/8" x 1/8" rubber plugs that he said he found on bench after cleaning the carb, ( yes he took it apart and cleaned it ) he was told they are parts from the carb but was beyond him to know where they went in it. It is a Honda 16.5 HP with 2 barrel(###)!
Submitted: 2 years ago.
Category: Small Engine
Expert:  Curtis B. replied 2 years ago.
Welcome to JUST ANSWER small engines, let me try to help you !! Thee plugs may have nothing to do with problem. There is a solenoid i the carburetor, is this solenoid opening as soon as the key is turned on? Has to have 12 volts to open, and it has to stay open as long as the key is on.
Customer: replied 2 years ago.
Thanks for the answer, however, since I asked I found out that the "plugs" are sort of a check valve and they go in the vent system on top of the carb interestingly I could not find out why. My guess is to stop carb icing or have something to do with high altitude use. It took me awhile and I'm sure you know we find alot of problems by accident, which I did. It turns out the intake manifold spacer gasket closest to the engine was missing a small piece on the back side which I couldn't see from the front. The only reason I left it on the engine was there wasn't a new one in the kit. Anyway it caused a vacuum leak hence it would only run on choke. I made a new one installed it and it runs just fine. To prove my theory I started it and let it run on full choke and then introduced small amounts of propane from a small torch around the outside of the carb. Sure enough the rpms went up and I could open the choke while the engine fed off the propane at the leak. I have worked on small engines for years and I still learn something new each time. So you were correct about the plugs we just needed to dig a bit deeper. I hope both of our answers help someone else in the future. Thank You, ***** *****
Expert:  Curtis B. replied 2 years ago.
Good job! Thanks for the update!