12hp Gravely
- Thread starter dnj12345
- Start date
TedLaRue
Gold Member
You haven't given us much to go on, but here are some of suggestions:
1) If the timing is incorrect (not advanced enough) an engine will idle "fine" but not have power.
2) If the carburetor's float is out of adjustment (needle worn, or lever bent) the engine could be starved for fuel under load but run "fine" at idle.
3) A bad spark plug wire (or even a bad spark plug) could also cause the engine miss firing. Spark plugs can be "bad" even if their physical appearance seems ok.
1) If the timing is incorrect (not advanced enough) an engine will idle "fine" but not have power.
2) If the carburetor's float is out of adjustment (needle worn, or lever bent) the engine could be starved for fuel under load but run "fine" at idle.
3) A bad spark plug wire (or even a bad spark plug) could also cause the engine miss firing. Spark plugs can be "bad" even if their physical appearance seems ok.
Treemonkey1000
Veteran Member
TedR gave you some good advice there. Another thing to watch for is a clogged airfilter. It may look ok but be saturated in the core. Also look for carb leaks to the head. Old gaskets can dry out and you get air leaks around them. What I have done is used WD 40 or carb cleaner. Then spray it around where the carb bolts to the intake tube and around where it bolts to the heads. Rev the engine up to a decent RPM while you are doing this. If the RPM's start fluctuating you probably have a leak there.
RalphVa
Super Member
- Joined
- Dec 19, 2003
- Messages
- 7,873
- Location
- Charlottesville, VA, USA
- Tractor
- JD 2025R, previously Gravely 5650 & JD 4010 & JD 1025R
I had a 12 hp Gravely that had a rough idle. Some Seafoam in the tank cleared that up. My Lawnboy engine was giving troubles with running at speed. Seafoam fixed it,too; same for my walkbehind JD mower. It had separate problems with speed and idle at different times.
On these Gravelys, you sometimes have to set the point gap a little less than the 0.20 that is specified. Otherwise, they never close. If not set right, generally it won't start at all, but maybe something to look at. On mine, I had to set the gap about 0.18.
Ralph
On these Gravelys, you sometimes have to set the point gap a little less than the 0.20 that is specified. Otherwise, they never close. If not set right, generally it won't start at all, but maybe something to look at. On mine, I had to set the gap about 0.18.
Ralph
TedLaRue
Gold Member
Older Gravely's used a magneto and the timing could be adjusted. However, the shaft that opens the points on your Kohler engine may be gear driven from the crankshaft. If so, the timing is affected only by the gap in the points, and there is no other adjustment.
Your problem could be ignition-related, or it could be fuel-related. You can download service manuals (free) from Kohler Engines: Owners & Service Manuals: Manuals & Maintenance
Fuel:
Did you adjust the carburetor?
Electrical:
Your spark plug fires when the points open. If the gap is too small, it will fire at the wrong time. If the gap is too wide, the points won't be closed long enough to charge the coil and you'll have a weak spark and it will fire at the wrong time.
When the points open, there is an arc across the gap. Over time this deposits metal from one side of the points to the other. That messes up the point gap. You can use a file or use emery cloth to smooth them up, or you could replace them.
There is a condensor (small metal cylinder) near the points which acts like an electronic sponge to dampen "back emf" (reverse voltage) which occurs when the points open. I doubt if that is your problem, because when it goes bad you probably wont' get any spark at all.
Another part of the ignition system is the coil. When the points are closed, current through the coil creates a magnetic field. When the points open, that field collapses and creates the spark on the secondary side of the coil which is connected to the spark plug. If the coil goes bad (e.g., internal windings short together), then the spark could be weak and misfiring could occur.
Finally, the wire from the coil to the spark plug could be bad. That could cause misfiring. If you have a way of measuring resistance (ohm-meter), the resistance in the wire should be 10,000 to 15,000 ohms per foot
Your problem could be ignition-related, or it could be fuel-related. You can download service manuals (free) from Kohler Engines: Owners & Service Manuals: Manuals & Maintenance
Fuel:
Did you adjust the carburetor?
Electrical:
Your spark plug fires when the points open. If the gap is too small, it will fire at the wrong time. If the gap is too wide, the points won't be closed long enough to charge the coil and you'll have a weak spark and it will fire at the wrong time.
When the points open, there is an arc across the gap. Over time this deposits metal from one side of the points to the other. That messes up the point gap. You can use a file or use emery cloth to smooth them up, or you could replace them.
There is a condensor (small metal cylinder) near the points which acts like an electronic sponge to dampen "back emf" (reverse voltage) which occurs when the points open. I doubt if that is your problem, because when it goes bad you probably wont' get any spark at all.
Another part of the ignition system is the coil. When the points are closed, current through the coil creates a magnetic field. When the points open, that field collapses and creates the spark on the secondary side of the coil which is connected to the spark plug. If the coil goes bad (e.g., internal windings short together), then the spark could be weak and misfiring could occur.
Finally, the wire from the coil to the spark plug could be bad. That could cause misfiring. If you have a way of measuring resistance (ohm-meter), the resistance in the wire should be 10,000 to 15,000 ohms per foot
Try a new epoxy sealed condenser. If that doesn't cure the stalling. have the coil tested.