Gravely-L engine problem

[mikluha]

Hi,

I have Gravely model L, two-wheel tractor with lawn mower attachment. Around 1965 with bendix carburetor.
Recently it started to shut itself after a while.
It starts perfectly, run smooth on idle. Until I turn attachment and start mowing.
It runs rough and shut itself after 2-3 min. I can press throttle all the way - doesn't help.
The carburetor seems to be adjusted. I followed the manual.
Spark plug is clean
Fuel is fresh.
Where should I start looking?

 

[oldmech]

Hi! Check for Gas Flow . Drain Carburator and look for good flow. Check air vent on gas cap. Good luck! Oldmech

 

[RichardTX]

If choking the carb does not help when it starts running rough, I would take a look at the ignition.

 

[Squeak n Itch]

Had almost the same problem a year or two ago. The suggestion to check gas flow was perfect. When it stalls, open the gas cap and try to restart with the cap loose. I ended up drilling a tiny air vent in the cap. It didn't occur to me that the problem started when I replaced the gas tank cap (with a non-vented version)!

If that is ineffective remove the small tube feeding gas to the carb. if you can get a cup or so of flow the problem is most likely in the carb and not the tank.

The problem showed up more with a full tank of gas. Drew a vacuum more quickly.

 

[Happypappy50]

Along with the fuel flow, points/condensor issues as addressed above ..... also check the PLUG WIRE GROMMET atop the cylinder head. If the wire has a hairline "crack" or other deterioration where it passes through the grommet, under a load the spark may "leak" from the wire and seek a path of lessor resistance via the grommet retainer if the rubber grommet is worn. Will run fine no-load ..... under load causes increased resistance to spark at plug gap ------> poor wire/grommet quality can be lessor resistance thereby eroding spark quality which may result in incomplete or poor combustion.

NOT very common ....... but you may consider ruling this out by simply assuring the plug wire is out of the grommet and not touching any other metal surface and give it a try. I've seen Einstein by-the-book mechanics spend hours and tons of $$$ replacing parts and still not solve a simple problem.

 

[RichardTX]

Sounds like a fuel delivery problem to me. Take the plug out of the bottom of the carb bowl and make sure that gas flows freely for about 20 seconds. It will come quick at first as you empty the bowl but you should have a pretty good flow. If it slows to a trickle, then something is likely partially clogged or occluded.