Tractor Only Operates When Choked

BillBee · May 10, 2007

I have a Craftsman 18HP garden tractor with a DOHC Twin Cylinder Briggs & Stratton engine which is running rough. This week the tractor ran fine during the first few hours of operation, but when using the following day, the tractor stalls when fully opening the choke and now will only operate if the choke is mostly closed. It has done this in the past but corrected itself over time. I am assuming it’s a carburetion problem, but not certain.

The tractor’s only use over its 17 year life span was for snow plowing operations. The tractor has not been used since March of 06 (no snow in RI this past winter) but is housed in a heated garage. Fuel and oil was changed prior to this years start up. The tractor is in exceptional condition. The tractor will now be used for grass mowing in addition to snow plowing. Any thoughts or suggestion on correcting the problem?

Bird · May 10, 2007

I'm not familiar with that particular engine and a lot of carburetors no longer have any adjustment, but in the past at least, when an engine would only run when partially choked, that simply meant that it was not getting enough gas for the amount of air going it, and the carburetor needed to be adjusted a little richer. So the first thing I'd do is see whether or not the carburetor is adjustable, and I'd trace the fuel line from the carburetor back to the tank. I'd be looking for two things; one is any restriction, stopped up filter, kinked line, etc. and the other is any cracks or breaks in the fuel line. Sometimes a partially broken fuel line lets air be sucked in rather than fuel leaking out, and air being sucked in will result in a too lean condition.

That's about all I can think of; maybe someone else has some better ideas.

ultrarunner · May 11, 2007

I've found cleaning sediment from the carb fuel bowl will take care of your problem... especially true with equipment that was running well the last time you used it and has since been sitting around.

Fuel bowl removal can be as simple as removing a single bolt. Generally, there is no need to remove the carb from the motor to remove the fuel bowl.

Once you have the bowl off, try a squirting a little carb cleaner from an aerosol can around the jet and you should be good to go. If you can't easily blow through it, then it is at least partially blocked.

Also, verify that you have a free flow of fuel to the carb.

It only takes a few particles of sediment to cause trouble.

BillBee · May 11, 2007

Bird and Ultrarunner thank you for the helpful suggestions. I will do as recommended and hopefully this will resolve the problem. I will keep the thread advised.

BillBee · May 14, 2007

You were right! I disconnected and air blew all lines discovering a small crack at the filter connection and repaired it by cutting it off. Gently air blew and cleared the fuel pump, which appeared to be blocked. I disassembled and removed the top portion of the carburetor and removed contaminates from its bowl. Reassembled, reconnected, fired it up, made adjustments with air and idle and it ran like a champ. The tractor was hauled to the weekend place for its new summer mowing operation tasks.
This is only the second time the cutting deck has been on the tractor, which now will occur annually. This 17 year old tractor owes me nothing. This tractor has been pretty much problem free for years and I always jump started it when needed for snow plowing in RI. So, I bit the bullet and bought a battery.

Thanks again guys.