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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 29855
Experience:  Service manager and technician for all brands of engines with 40 + years of experience.
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My ride-on mower (Lawnflight) recently had new engine of different

Customer Question

My ride-on mower (Lawnflight) recently had new engine of different type fitted. Since having this replacement the engine starts and runs well enough but peters out after 20 minutes i.e not an abrupt stop but a running down as if short of fuel. Leaving the engine off for about 15 minutes I can start and continue till I have finished the grass cutting (about another 10 minutes). I have removed the bonnet so as to allow more air to be drawn in by cooling fan but makes no difference. The company who fitted the engine are baffled themselves. The new engine is a Loncin 764 cc V-Twin. One can almost set ones watch by the duration on run time before stopping since it always 20 minutes after starting.
Submitted: 1 year ago.
Category: Small Engine
Expert:  Curtis B. replied 1 year ago.
With twin engine, likely is a fuel problem. Does the carb have an electric solenoid in it? Solenoid would be anti-backfire solenoid , and plugs the main carb jet when it is closed. It would open as soon as key is turned on. Listen for the click when you turn the switch on. Then when it quits, turn key on and off and listen for the click. No click , no fuel! Also have you checked the vent in the fuel tank cap? Tank may be drawing a vacuum and the engine would starve for fuel. When unit quits, loosen the fule cap and see if it has vacuum, it should NOT. With lack of fuel, I think either the fuel solenoid is bad, or the fuel cap is not venting.
Customer: replied 1 year ago.
Am away from home for next few days so cannot investigate until I return. I think we can discount the fuel cap causing a vacuum since I can start it again after about 10 minutes. If the problem is the solenoid does it mean that the engine should start again immediately after stopping. I thought perhaps it may be caused by engine overheating i.e. would there be such a thing as a thermal cutoff ?
Expert:  Curtis B. replied 1 year ago.
Do not discount the fuel cap,as that is way it would act. Solenoid ay or may not let it immediately restart.