update on 18.5 HP briggs

[Dan in Ore]

I have an 18.5 HP briggs INTEK single cylinder on a riding lawn mower. When it gets hot, the engine starts cutting out. I have done the obvious, fuel filter, tank and spark plug all to no avail.

One response I got on this forum suggested that the valve lash may be too tight and when it warms up, the valves aren't closing properly. Today I adjusted the valves and ran it without the hood and no problem. Put the hood back on and the problem returned.

Tomorrow, I will remove the hood and see if the problem goes away again. If it does, I guess the Magnatron is next. Thanks to all for the help.

Dan

 

[El Toro]

Check to see if you have fire to your plug asap when it quits before the engine cools off. Could be the magnatron failing when it gets hot. Hal

 

[Dan in Ore]

It doesn't quit, It acts like it's starving for fuel, but never completely quits. the only thing I haven't replaced or cleaned in the fuel system is the fuel shut off solenoid on the float bowl, but I hear those things either work or don't.

Thanks for the input.

Dan

 

[El Toro]

Check the fire to your plug when its losing power
see if has good hot spark. The heat may cause the magnatron to fail. Make sure there's no grass clippings, mouse nests or dirt under the fan shroud blocking the cooling air to your engine. Hal

 

[Dan in Ore]

I just did the lawn with the hood removed and it did fine, so it is heat build up that is causing the problem. Don't know how I can check the spark without the engine cooling down, besides the engine needs to be under load or it won't cut out.

Thanks for the advice Hal.

Dan

 

[joe csuti]

When Hal said to check spark when eng hot,he meant pull plug wire from plug,with a fuse puller or pliers & connect a spare plug & ground to block,have someone sit on tractor & crank eng or buy an inline ign tester & connect between plug & hv lead,start eng & watch tester(I paid .99 + 3.50 ship for my last one on ebay)if you can rig it up right so it doesn't short to block,leave it connected & run tractor that way,when eng starts cutting out you can look at tester & check spark,getting to/removing plug tough enough when eng cold,due to design of eng,muchless trying to remove plug when hot,another thing to check,if eng has an oil pressure sw on filter adapter/block,try disconnecting wire to same if loseing spark,sw may be going bad or filter may be plugged up & need replacement

 

[joe csuti]

As an after thought & some food for thought for the future,several yrs ago on another forum I'm on,several people had same problem on jd,cubs, and other knock off's made by mtd,weather you do/don't change coil,the basic problem is hood design + too much eng in a confined space setting up a feedback loop of hot discharge air being sucked back into eng by flywheel fan,what I suggested to them was install a small gable/soffet vent(home depot/lowes not pretty,but works) over flywheel cover on hood or goto jc whitney online & check out their hood scoops,this solved problem in all cases except 1 where coil was completely bad,the main idea being useing vent/scoop you're now pulling cool air from outside hood rather that hot air from under hood.

 

[El Toro]

If this tractor has ran ok up until now & just started doing this you could have some blockage
under the fan shroud. I know this from my own tractor. Here's what I found. Hal