Have you experienced a rich condition on cold starts or even hot starts, like black smoke? I have a 2021 gravely Mach with the fx921 and 10 hours that has the same plug readings. I am also getting black smoke on startups. I have installed new plugs and performed WOT cuts with no time idling, and get the same plug readings. Just wondering if you had any updates on a fix?
Do these look normal?
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VRR.DYNDNS>BIZ
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wHAT DO YOU MEAN "pLUG rEADINGS"
The overall condition of the plug that I can visually see.
Glades Cat
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Have you checked/ replaced the air filter. Of course, a plugged up filter will choke an engine.
Yea, they look sooty.
Yea, they look sooty.
Yeah, the mower is brand new. No obstructions in the intake to speak of. I think I have narrowed it down to the tank vents not relieving pressure from the tanks. I can remove the fuel caps on each tank and the pressure exhaust outta the tanks. The tank vent valves have a duck bill check valve that is restricting the pressure to relieve to the intake elbow. I believe the tanks are pressurizing during storage and during operation causing the fuel to force past the float needle. There was a puddle of fuel in the intake when I pulled the carb off.
VRR.DYNDNS>BIZ
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The system is for evaporative emissions. There are many designs. The typical new generators have a vent line to the air box connected to the valve on the top of the tank. Many people fill the tank to the top, not paying attention to the do not fill above point. If they do fill that above this point, then while running, this line can suck gas thru the system, usually hitting the charcoal cannister first, saturating it with gas , the non to the intake. For this system to draw gass fumes to the cannister to avoid the all damaging fumes to our air, a vacuum as well as static vent thru the cannister is designed to hold those fumes and when running, it tends on a proper system to dry the charcoal of anything collected. These systems are not perfect. As an example, a near full tank of gas, then being moved around can slosh gas into the system, and gravity then carries it to the cannister where it lays waiting for the next run, causing a very rich system. ON a mower, while being used this can be worse in that a full tank on a bumpy sloped travel is going to suck fuel in and feed fuel in excess.
Hammermechanicman
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You need to run the engine harder or run the next hotter step plugs.
Thank you, I am in the process of trying to find an older style vented cap with the same threads and deleting the evaporative vent line and plugging the vent valve.
It’s hard to actually run a mower harder than normal when they are governed to 3600. I believe mowing thicker grass would actually demand more fuel based on the increased load. I have tried the ngk BPR4ES which is one step hotter than the stock BPR5ES.
Hammermechanicman
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These engines have no temperarure regulation. They are designed to operate at full load at a fairly high ambient temperature. Spark plugs need to operate at about 1000 degrees to be in the self cleaning range. Engines not run at a high enough load to get the engine temp high enough will carbon foul plugs regardless of the mixture. Moat engines today are jetted on the lean side. How does the engine run? Black smoke? Missing? Stumbling on accelerating?