Newly Rebuilt K341 running rough

[WH1618speed 535]

We recently had this K341 rebuilt, and it runs really rough. I have tried resetting and gapping the points, cleaning them, and swapping them with points of a good-running K341 and a new one. I tried adjusting the carb by backing out the high idle 2 turns and the low 1 3/4 turns. (its not a Walbro). Tried a new spark plug. The only thing I haven't done yet is swapped carbs. I am wondering if when it was rebuilt, it wasn't timed correctly. It sounds like a misfire but it is very consistent at sparking the fuel at the wrong time. It gets really bad at low idle and almost dies. Gets better with an increase in throttle. Also using fresh no ethanol 90 octane gas. Any ideas or thoughts would be great. Thanks!

 

 

[Fordiesel69 263]

1. did you get the crank timed correctly to the camshaft?

2. are the vales good, and are they adjusted correctly?

3. do you have a temporary ground ties to the engine block ( on a bare spot) so that your ign system is operating correctly?

[kpinnc 12,004]

Try a new condenser just for giggles, and make sure the clip grounds well. They can make an engine run really rough. 

[WH1618speed 535]

1 hour ago, Fordiesel69 said:

1. did you get the crank timed correctly to the camshaft?

2. are the vales good, and are they adjusted correctly?

3. do you have a temporary ground ties to the engine block ( on a bare spot) so that your ign system is operating correctly?

I didn’t do the rebuild so I am not sure what was done. Valves were supposed to be adjusted to spec

Edited May 28 by WH1618speed

[WHX?? 48,814]

1 hour ago, Fordiesel69 said:

did you get the crank timed correctly to the camshaft?

 

Guys gotta wonder then if not off a tooth since you didn't set it. Done it myself once...

Guessing you tried the points a couple thousand either side of .020? Maybe try static timing? 

[Pullstart 62,834]

Maybe get the engine builder involved?

[953 nut 55,187]

With a battery ignition system, the ignition points are closed the majority of the time. With the points closed and the ignition switch ON the primary windings of the ignition coil have current flowing through them and are developing a magnetic field in the iron core of the ignition coil. The moment the ignition points open the magnetic field collapses and induces a momentary high voltage pulse in the secondary windings of the coil which goes through the spark plug wire and arcs across the gap of the spark plug. If this occurs in the presence of a compressed fuel/air mixture of the proper ratio an explosion will occur within the cylinder. If this explosion occurs at the proper time in the engine’s cycle there will be pressure applied to the piston forcing it downward on the power stroke. The ignition points will continue to open further after this has occurred. How far they open is immaterial, their work has been done for that cycle of engine operation. What is important is when they open relative to the position of the piston on its compression/power revolution. If it occurs too soon there will be backfiring, too late and there will be a reduction of power. In the case of our Kohler engines the sweet spot is twenty degrees Before Top Dead Center, that is what the “SP” mark on the flywheel is set. At the moment the points open the condenser quenches the arc across the points extending their life, the rest of the time it just sits there.

Static timing can be done with Kohler engines that do not have a Spark Advance camshaft. The instructions in the Kohler Engine Service Manual for static timing of the later ACR camshaft engines calls for an Ohm Meter to be used. I prefer a 12 Volt Test Light. The light will be connected between the battery “+” terminal and the lead that connects the points to the coil (disconnected from the coil). When the points are closed the light will be on, the moment the points open the light will go off. You don’t have to be focused on it like you would on a meter. With the test light situated near the sight hole for the flywheel (spark plug out so the engine will turn with ease), turn the flywheel slowly by hand in the clockwise direction (counter-clockwise if on the PTO end) until the moment the light goes out. If the “SP” mark is centered in the hole you are done, if not you have a little work to do. If the points are opening too late, they need to be opened further, if it occurs too early they need to be closed up some. Make gradual adjustments until the “SP” mark on the flywheel is centered in the sight hole at the moment the light goes out. Now tighten the screw securely and turn the engine over several revolutions to be sure the points are consistently opening at the proper moment.

[peter lena 8,608]

@WH1618speed  regularly use ,  BOLT ON ELECTRICAL LUGS , on my engine / frame to battery ground point , never count on the  AIR COOLING TINS to carry a ground , ant rusty point will limit  current , also use a dielectric  lube on threading , also helps headlight  grounding , pete 

 

[WH1618speed 535]

11 hours ago, WHX?? said:

Guys gotta wonder then if not off a tooth since you didn't set it. Done it myself once...

Guessing you tried the points a couple thousand either side of .020? Maybe try static timing? 

Yep I tried that, and points off of one than ran good.

[WH1618speed 535]

4 hours ago, 953 nut said:

With a battery ignition system, the ignition points are closed the majority of the time. With the points closed and the ignition switch ON the primary windings of the ignition coil have current flowing through them and are developing a magnetic field in the iron core of the ignition coil. The moment the ignition points open the magnetic field collapses and induces a momentary high voltage pulse in the secondary windings of the coil which goes through the spark plug wire and arcs across the gap of the spark plug. If this occurs in the presence of a compressed fuel/air mixture of the proper ratio an explosion will occur within the cylinder. If this explosion occurs at the proper time in the engine’s cycle there will be pressure applied to the piston forcing it downward on the power stroke. The ignition points will continue to open further after this has occurred. How far they open is immaterial, their work has been done for that cycle of engine operation. What is important is when they open relative to the position of the piston on its compression/power revolution. If it occurs too soon there will be backfiring, too late and there will be a reduction of power. In the case of our Kohler engines the sweet spot is twenty degrees Before Top Dead Center, that is what the “SP” mark on the flywheel is set. At the moment the points open the condenser quenches the arc across the points extending their life, the rest of the time it just sits there.

Static timing can be done with Kohler engines that do not have a Spark Advance camshaft. The instructions in the Kohler Engine Service Manual for static timing of the later ACR camshaft engines calls for an Ohm Meter to be used. I prefer a 12 Volt Test Light. The light will be connected between the battery “+” terminal and the lead that connects the points to the coil (disconnected from the coil). When the points are closed the light will be on, the moment the points open the light will go off. You don’t have to be focused on it like you would on a meter. With the test light situated near the sight hole for the flywheel (spark plug out so the engine will turn with ease), turn the flywheel slowly by hand in the clockwise direction (counter-clockwise if on the PTO end) until the moment the light goes out. If the “SP” mark is centered in the hole you are done, if not you have a little work to do. If the points are opening too late, they need to be opened further, if it occurs too early they need to be closed up some. Make gradual adjustments until the “SP” mark on the flywheel is centered in the sight hole at the moment the light goes out. Now tighten the screw securely and turn the engine over several revolutions to be sure the points are consistently opening at the proper moment.

Really helpful, Thanks!

[rmaynard 15,434]

And I might add, if you have lined up the crank and cam properly, the SP or S mark will be in the right place when the points, set to .020, open. If the SP or S mark is way off, you may have assembled the engine wrong. Also, don't make the mistake of rotating the engine in the wrong direction. Checking the timing must be done rotating the engine in the clockwise direction if viewing from the flywheel side, or counter-clockwise rotating from the PTO side.

 

 

 

Edited May 28 by rmaynard