One of my crew put my bad boy maverick with a Koehler ZT740 into a pond. It bent both piston arms but everything else seemed to be ok. I replaced the piston rods, one of the pistons and put everything back together. The mower starts and runs but gets extremely hot. So hot that it has started to melt the throttle cable. Any ideas on what is wrong?
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Koehler ZT740 in a pond
- Thread starter Ebtate8
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Export threadbertsmobile1
Lawn Royalty
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I would suspect that the timing is out
Chronic overheating comes from timing being too far advanced or fuel ratio way too lean
Too far retarded will also cause overheating , but before that happens it will blow a lot of black smoke.
What do the spark plugs look like ?
Chronic overheating comes from timing being too far advanced or fuel ratio way too lean
Too far retarded will also cause overheating , but before that happens it will blow a lot of black smoke.
What do the spark plugs look like ?
VegetiveSteam
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I've dealt with quite a few Kohler engines that had been driven into lakes and ponds and I've never seen one bent connecting rod let alone two. That's really bizarre to me. The ones I really loved were the people who wanted warranty on the engine because they drove the equipment into the water. Anyway I digress.
If the engine was stopped so abruptly that it bent the connecting rods, I would feel that since you can't stop the inertia of a flywheel that quickly, the flywheel key is sheared and the engine is out of time like Bert said. Have you had the flywheel off? And again like Bert mentioned, what do the spark plugs look like? If the engine is truly running hot then they should not look normal. They will typically look pretty clean with grey or white ash deposits on them. If the spark plugs look normal and nothing besides the throttle cable sheathing is melting, check your grounds. I've seen throttle and choke cables light up like a toaster element due to a poor ground.
If the engine was stopped so abruptly that it bent the connecting rods, I would feel that since you can't stop the inertia of a flywheel that quickly, the flywheel key is sheared and the engine is out of time like Bert said. Have you had the flywheel off? And again like Bert mentioned, what do the spark plugs look like? If the engine is truly running hot then they should not look normal. They will typically look pretty clean with grey or white ash deposits on them. If the spark plugs look normal and nothing besides the throttle cable sheathing is melting, check your grounds. I've seen throttle and choke cables light up like a toaster element due to a poor ground.
Spark plugs are fine. The flywheel key was not sheared. How do I adjust the timing? The engine is definitely grounded. It’s so got that you can’t get near the back end of the mower. I am in desperate need of getting this back up and running. I mowed with it for about 30 minutes after it was back together. It started losing power which I assume was due to the overheating.
This service manual may be of some help. https://resources.kohler.com/power/kohler/enginesUS/pdf/16_690_01_EN.pdf
VegetiveSteam
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You had they flywheel off when you checked the key?
VegetiveSteam
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Well, if the key is good then ignition timing should be good as long as the air gap on the ignition modules is correct. The only other timing is valve timing and that shouldn't change as long as you got the timing marks on the cam and crank aligned properly. There is a very slim chance the gear on the crankshaft turned on the crankshaft. That would put it out of valve time. Normally that would create a running issue and would lack power.
You can check valve timing fairly easily by pulling the rocker cover off of one side. Turning the flywheel by hand, bring that sides piston up to TDC on the exhaust stroke. At TDC exhaust, both valves should be slightly open. That's called valve overlap. If you move the flywheel back and forth the rocker arms should do sort of a teeter totter. If you get valve overlap at any point other than TDC exhaust stroke, the valves are out of time. That means that unless the timing marks aren't aligned, the gear on the crankshaft has turned on the crankshaft and you would now need a new crankshaft. If you end up needing to replace the crankshaft it is highly recommended to replace the camshaft also. If not you could end up with a noisy engine at best and at worst, you could end up with a cracked crankshaft gear, which will cause the gear to turn again, and you're pretty much back where you started.
I doubt this is your scenario but if you feel it's a timing issue, valve overlap would be the next thing I would check. I'll take it for granted you are running it with the blower housing on and all the baffles in place?
You can check valve timing fairly easily by pulling the rocker cover off of one side. Turning the flywheel by hand, bring that sides piston up to TDC on the exhaust stroke. At TDC exhaust, both valves should be slightly open. That's called valve overlap. If you move the flywheel back and forth the rocker arms should do sort of a teeter totter. If you get valve overlap at any point other than TDC exhaust stroke, the valves are out of time. That means that unless the timing marks aren't aligned, the gear on the crankshaft has turned on the crankshaft and you would now need a new crankshaft. If you end up needing to replace the crankshaft it is highly recommended to replace the camshaft also. If not you could end up with a noisy engine at best and at worst, you could end up with a cracked crankshaft gear, which will cause the gear to turn again, and you're pretty much back where you started.
I doubt this is your scenario but if you feel it's a timing issue, valve overlap would be the next thing I would check. I'll take it for granted you are running it with the blower housing on and all the baffles in place?
Pulled the flywheel again today and found the key was sheared. Timing has been way off as a result. I’m sure I can get some keystock at a local auto parts house. Anyone have any idea how big that key is? It was completely obliterated and I have nothing to go on. All parts diagrams only show a part number. No dimensions. Thanks for all the help guys!Well, if the key is good then ignition timing should be good as long as the air gap on the ignition modules is correct. The only other timing is valve timing and that shouldn't change as long as you got the timing marks on the cam and crank aligned properly. There is a very slim chance the gear on the crankshaft turned on the crankshaft. That would put it out of valve time. Normally that would create a running issue and would lack power.
You can check valve timing fairly easily by pulling the rocker cover off of one side. Turning the flywheel by hand, bring that sides piston up to TDC on the exhaust stroke. At TDC exhaust, both valves should be slightly open. That's called valve overlap. If you move the flywheel back and forth the rocker arms should do sort of a teeter totter. If you get valve overlap at any point other than TDC exhaust stroke, the valves are out of time. That means that unless the timing marks aren't aligned, the gear on the crankshaft has turned on the crankshaft and you would now need a new crankshaft. If you end up needing to replace the crankshaft it is highly recommended to replace the camshaft also. If not you could end up with a noisy engine at best and at worst, you could end up with a cracked crankshaft gear, which will cause the gear to turn again, and you're pretty much back where you started.
I doubt this is your scenario but if you feel it's a timing issue, valve overlap would be the next thing I would check. I'll take it for granted you are running it with the blower housing on and all the baffles in place?