I was recently given a non-running Huskee 42" mower with a Briggs knock-off MTD engine called Powermore 420CC.
The owner said it ran about 6 months (he bought it in the summer of 2015 but it didn't last the summer).
I hooked up a battery and the engine cranked normally but no start - not even a cough.
My first diagnostic step was to remove the valve cover since a "repair man" told the prior owner it wasn't worth repairing. Lo and behold, I found that the intake rocker arm was missing. Ordered the part - set the valves and the engine would not turn over even though it had without the rocker arm. I noticed when I rotated the engine by hand that it would turn but not make a full revolution.
My next inspection step was to remove the head. Everything looked good except there was an excess of carbon on the piston and inside the head. Ok, I'll clean that later. However, that wouldn't stop an engine from rotating so I was now thinking something really bad was wrong in the engine.
I took the bottom cover off and was pleased to see it actually has an oil pump versus a slinger. Everything looked perfect in there - no metal shavings, no sludge, no dirt, it was spotless and all parts looked excellent. Since there must be a problem with the valve train, I pulled the cam. Like everything else, it was in perfect condition, at least to my naked eyes. No flat spots or signs of wear.
So it freely cranked without an intake rocker arm but would not crank with the rocker arm. The cam was good, I better look more closely at that intake valve. So I removed the keeper but the valve didn't budge. The excess carbon had actually caused the valve to freeze closed in the guide. After a few taps on the inside end of the valve and its out for a closer inspection. Surprisingly, the valve looks to be in excellent condition once all the carbon is removed.
Reassemble the engine, install it on the mower, drain the gas and replace with fresh and crank and crank and crank. Nothing and I mean it didn't hit a stroke a single time. It had air (no air filter), gas (unburned gas was coming out of the exhaust port - muffler not installed) and spark. I had put one of those inline spark testers and it sparked just fine. Thinking maybe the spark was weak, I reset the gap to .0010". That didn't change the spark as I had used the old business card trick earlier.
Ok, so the spark is not sparking at the correct moment so I pulled the flywheel to make sure the key was installed and not sheered. It also was in perfect condition.
Getting desperate (even though it was sparking) I pulled the kill wire off of the coil. On the next start attempt the engine fired 2-3 times but did not actually start. Scratching my bald head - how could disconnecting the kill wire impact the engine as it was sparking before. I came to the conclusion it was just a fluke because after many attempts to start it only coughed twice, both times firing 2 or 3 times. I am convinced it was a bad coincidence that it fired the first time after I disconnected the kill wire.
So here I am - cranking with a properly timed spark, gas in the cylinder and free air but no start.
Diagnostic ideas are welcome. I think my next step is to clean/service the carb. Maybe I have gas but not being properly delivered.
The details on the machine are in the attachments. The engine model is 4P90HUB. Single cylinder B&S clone.
The owner said it ran about 6 months (he bought it in the summer of 2015 but it didn't last the summer).
I hooked up a battery and the engine cranked normally but no start - not even a cough.
My first diagnostic step was to remove the valve cover since a "repair man" told the prior owner it wasn't worth repairing. Lo and behold, I found that the intake rocker arm was missing. Ordered the part - set the valves and the engine would not turn over even though it had without the rocker arm. I noticed when I rotated the engine by hand that it would turn but not make a full revolution.
My next inspection step was to remove the head. Everything looked good except there was an excess of carbon on the piston and inside the head. Ok, I'll clean that later. However, that wouldn't stop an engine from rotating so I was now thinking something really bad was wrong in the engine.
I took the bottom cover off and was pleased to see it actually has an oil pump versus a slinger. Everything looked perfect in there - no metal shavings, no sludge, no dirt, it was spotless and all parts looked excellent. Since there must be a problem with the valve train, I pulled the cam. Like everything else, it was in perfect condition, at least to my naked eyes. No flat spots or signs of wear.
So it freely cranked without an intake rocker arm but would not crank with the rocker arm. The cam was good, I better look more closely at that intake valve. So I removed the keeper but the valve didn't budge. The excess carbon had actually caused the valve to freeze closed in the guide. After a few taps on the inside end of the valve and its out for a closer inspection. Surprisingly, the valve looks to be in excellent condition once all the carbon is removed.
Reassemble the engine, install it on the mower, drain the gas and replace with fresh and crank and crank and crank. Nothing and I mean it didn't hit a stroke a single time. It had air (no air filter), gas (unburned gas was coming out of the exhaust port - muffler not installed) and spark. I had put one of those inline spark testers and it sparked just fine. Thinking maybe the spark was weak, I reset the gap to .0010". That didn't change the spark as I had used the old business card trick earlier.
Ok, so the spark is not sparking at the correct moment so I pulled the flywheel to make sure the key was installed and not sheered. It also was in perfect condition.
Getting desperate (even though it was sparking) I pulled the kill wire off of the coil. On the next start attempt the engine fired 2-3 times but did not actually start. Scratching my bald head - how could disconnecting the kill wire impact the engine as it was sparking before. I came to the conclusion it was just a fluke because after many attempts to start it only coughed twice, both times firing 2 or 3 times. I am convinced it was a bad coincidence that it fired the first time after I disconnected the kill wire.
So here I am - cranking with a properly timed spark, gas in the cylinder and free air but no start.
Diagnostic ideas are welcome. I think my next step is to clean/service the carb. Maybe I have gas but not being properly delivered.
The details on the machine are in the attachments. The engine model is 4P90HUB. Single cylinder B&S clone.
