Scag scz61v-34kh hard to crank

[crazy Greg]

I have a Kohler engine 34KH Serial# 4630606611, cranks slow when it come up on the compression stroke, has anyone else have this problem, how did you solve it? this engine has self adjusting lifters so they cannot be adjusted like the old style. Installed new battery, cleaned the battery & starter terminals, made no difference, cam does not have the ACR according to Kohler. Thanks for any feed back given.

 

[Rivets]

There are three things I would be checking. First, check the negative cable to chassis connection, making sure it is extremely clean and tight. Second, I would hook my meter across the battery and while cranking check the battery voltage. It should not drop below 10 VDC while cranking. Third, if the voltage is good I would hook the meter across the starter + connection and a good ground and check the voltage drop at the starter. Again it should not drop below 10 VDC. When you post back make sure you include all numbers off the unit and engine. I’m not finding a unit with the serial number you posted.

 

[crazy Greg]

I added two other ground cables from the engine to the battery.Voltage does not drop below 10 VDC when cranking at the battery or starter, I seen another Thread that you should check for a bad ground by putting the negative cable to ground & positive cable to the starter housing from your meter & see if it reads any voltage, and it does. The only other numbers I can find is SPEC NO. 6252306, Serial NO. 4630606611. Take your voltmeter and simply attach the black lead to the negative terminal of the battery. Then take the red lead of your meter and touch it someplace on the case of the starter that is unpainted. Typically, I usually go to the drive end housing near the mounting bolts. Crank the engine and see if you read any voltage. You should read zero. If you do read voltage, then you have a compromised ground. Possibly where the ground cable connects to the equipment. Ground issues are pretty common on some of these pieces of equipment so it’s always a good idea to eliminate that first as it’s very easy to do and might save you from chasing other things that aren’t actually a problem.
This is the thread that I was talking about.

 

[Rivets]

From your readings we can rule out an electrical problem. I would now remove the spark plug and see if it spins over. If it does we have to look into a compression problem. This service manual may help you out. https://resources.kohler.com/power/...023.782932257.1703450689-820762062.1703450689

 

[VegetiveSteam]

Kohler had an ignition timing issue with some of the big block engines causing them to hang up when cranking. It was a rare enough issue that Kohler never tried to find a fix for it. That left folks in the field to try and come up with a solution.

Leave the spark plugs in but remove the spark plug wires from the spark plugs and ground them. Now try cranking the engine over and see if the issue goes away. This way you are still cranking the engine under full compression, but you've taken ignition out of the equation. If it cranks fine the starter and electrical system are probably okay. At this point widening the gap between the ignition modules and the flywheel to about .018 will probably take care of the issue.

The issue was seen on more Exmark units than anything else, but Exmark was also the largest user of the Kohler big block. I worked with an Exmark dealer in IL and one in LA who were both dealing with this issue. They both found that when they disconnected the spark plug wires but left the spark plugs installed, the engines turned over just fine. The dealer in IL made an offset flywheel key and found that took care of the issue but caused the engine to lack power at full throttle. Changing the air gap on the ignition modules will also change timing. Both dealers found that at .015 air gap, the issue was less but still there although to a lesser extent. At .018 air gap they found the issue to be gone and had no issues with lack of power at full throttle under load.

 

[Rivets]

Veg, thank you for this info. To be truthful I’ve never heard of this problem, but have worked on very few Exmark units. Just another piece of info I’ll have to file away in this aged brain. Never to old to learn, but at this age learning is not the problem, remembering is.

 

[crazy Greg]

Thanks for the great tip, I will try that this weekend and then post my results.

 

[VegetiveSteam]

Thanks for the great tip, I will try that this weekend and then post my results.

Yeah, just start with trying to crank the engine with the plug wires removed from the spark plugs and see if that helps anything. If it doesn't then there is no need to mess with air gap.

 

[crazy Greg]

I pulled the plug wires, cranked it over as if starting and it did crank better so I did the adjustment of the air gap and cranked it over without plug wires, seen no difference. Put plug wires back on and cranked it to start and it came up on compression stroke and wanted to stop, this was done with full choke on, seems to crank better without the choke on but will not start without it. Could it be a carb issue while the choke is on?

 

[VegetiveSteam]

I wouldn't think the carb would have anything to do with it. Having the choke on reduces the amount of air being drawn in and in theory should reduce compression if anything. Reduced compression should actually make the engine turn over easier.

Did I read correctly that the engine did turn over easier with the plug wires removed?