Small Engines (Lawn Mowers, etc.): 318 Runs Rough, john deere 318, proper air flow

Question
Hi Howard,

I recently purchased an '87 John Deere 318 with the P218G Onan motor with about 800 hours. At first it would run for about 20-30 minutes then die and not start until cool. I replaced the ignition control module which resolved this issue. Now that it runs for extended periods another issue has surfaced. It starts, idles, and runs perfectly, however after 30 minutes or so, once the motor reaches normal operating temperature, the motor starts cutting out when going down hill or turning right. It does this with or without the mower deck engaged. On level ground it runs fine. Any ideas?

Thanks for you help!

Answer
So it sounds like your machine looses power on the downward slope, (particularly) and for some reason it doesn't care for right turns also.

Check the air intake for any blockages, dirt in filter, oil saturated filter, other debris.

Check the oil level, the viscosity of the engine oil, condition of oil. If necessary replace and top-up to the correct level.

Adjustment of the carburetor.  You may have to remove the carb for overhaul.

Check the exhaust for any restrictions stopping proper air flow.

Check engine valve lash.  Reset valves to correct lash.

Check valves for correct seating. Also Valve Guide Lash.  Overhaul valves and seats. Replace valves if necessary.

Check ignition timing.  Check flywheel for partial shearing.

Once you get through this series of trouble=shooting steps, get back to me.

Good luck,
Howard