HM100 woes
- Thread starter Scrubcadet10
- Start date
- Joined
- Sep 24, 2017
- Threads
- 266
- Messages
- 6,633
Will do
I would think that a 1-2 second miss would be hard to confirm as loss of spark when looking at a spark tester.
Appears you have done about everything but swap out the mag.
I'm assuming it's the electronic magneto engine and not the old model with points/condenser.
You mentioned it don't start easy. Them HM100's with manual only rope crank are not an easy start especially in cold weather and with the non-modded low emissions non-adjustable carb they usually hunt and surge for about 30 seconds in cold weather when first started.
Appears you have done about everything but swap out the mag.
I'm assuming it's the electronic magneto engine and not the old model with points/condenser.
You mentioned it don't start easy. Them HM100's with manual only rope crank are not an easy start especially in cold weather and with the non-modded low emissions non-adjustable carb they usually hunt and surge for about 30 seconds in cold weather when first started.
Check the govener
grumpyunk
Well-Known Member
- Joined
- Jul 13, 2015
- Threads
- 0
- Messages
- 104
Would you believe me if I said: "They all do that." Ha!
I would do two things. Take a file to the gap on the spark plug. Both the center electrode - the tip should have square corners, and the side electrode - if there is any rounding, it should be make flat where it faces the center electrode. Most plugs can be faced so they will work as new, especially in the old engines where the mixture is not leaned out by dictate from on high.
Second thing would be to run the thing in the dark to see if you have spark jumping to ground via the secondary wiring. By now, the wires are old enough for a slug of Old Burnside Raw Whiskey, and likely have had some degradation of the insulation and are primed to leak those milliamperes as fast as they can. Be sure also that the ceramic is clean on the outside as any sort of deposit can lead to the spark taking a shortcut. If it has points, use some emery paper folded and trapped using the spring tension to clean off any deposits or oxide. I still have the LAV running on points and I got it used in 1992. Have new points down in the mower parts box. I did clean them once since I got it. Maybe about the time I adjusted the valves when it would not start when warmed up. It seems to start on the first pull if I take off the air filter. New filter media on the way. It does not have a choke I can fiddle with and I do not know how it 'knows' to enrich itself when cold...
tom
I would do two things. Take a file to the gap on the spark plug. Both the center electrode - the tip should have square corners, and the side electrode - if there is any rounding, it should be make flat where it faces the center electrode. Most plugs can be faced so they will work as new, especially in the old engines where the mixture is not leaned out by dictate from on high.
Second thing would be to run the thing in the dark to see if you have spark jumping to ground via the secondary wiring. By now, the wires are old enough for a slug of Old Burnside Raw Whiskey, and likely have had some degradation of the insulation and are primed to leak those milliamperes as fast as they can. Be sure also that the ceramic is clean on the outside as any sort of deposit can lead to the spark taking a shortcut. If it has points, use some emery paper folded and trapped using the spring tension to clean off any deposits or oxide. I still have the LAV running on points and I got it used in 1992. Have new points down in the mower parts box. I did clean them once since I got it. Maybe about the time I adjusted the valves when it would not start when warmed up. It seems to start on the first pull if I take off the air filter. New filter media on the way. It does not have a choke I can fiddle with and I do not know how it 'knows' to enrich itself when cold...
tom
- Joined
- Sep 24, 2017
- Threads
- 266
- Messages
- 6,633
No change
At this point it’s time to look for stupid, but I’m drawing at straws here. Does your carb have a black plastic cover over the idle jet? If so have you removed the idle jet and made sure the jet is open in both directions? Or, swap out the jet from a different carb. What color is the spark plug? Is it showing a rich (black) or lean (white) running condition? Seeing that adding choke makes no difference, I’m wondering if we need to lean out the carb a little, by lowering the float level. Finally I’d try a resistor plug and see what happens. Yes, I’m looking like a nincomepoop here.
- Joined
- Sep 24, 2017
- Threads
- 266
- Messages
- 6,633
Does your carb have a black plastic cover over the idle jet? Yes, jet has been removed and cleaned.
What color is the spark plug? Tan-ish brown.
I’d try a resistor plug and see what happens: Tried a resistor, BR2LM.
What color is the spark plug? Tan-ish brown.
I’d try a resistor plug and see what happens: Tried a resistor, BR2LM.
You should see me.
Hammermechanicman
Lawn Addict
- Joined
- Jan 10, 2020
- Threads
- 65
- Messages
- 3,828
Does it miss at idle? WOT? loaded? Unloaded? Sprayed brake kleen around the intake manifold? Will coil jump a 1/4" gap in air?
I would hookup an online neon spark tester and remove the air cleaner and muffler. Start the engine and let it idle. If it is a spark problem it should be observable at the spark tester. If it is an exhaust valve problem it will pop in the exhaust when it misses. If an intake valve problem it will pop back through the carb when it misses.
I would hookup an online neon spark tester and remove the air cleaner and muffler. Start the engine and let it idle. If it is a spark problem it should be observable at the spark tester. If it is an exhaust valve problem it will pop in the exhaust when it misses. If an intake valve problem it will pop back through the carb when it misses.
VegetiveSteam
Well-Known Member
- Joined
- Jun 1, 2022
- Threads
- 0
- Messages
- 446
Do you think it's something that we could hear if you posted a video?