A case study Craftsman YT4500

BruceTX

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Hello, I am a newbie to this forum. I need help figuring out my YT4500's issues. There seems to be multiple issues with this mower. I was given this mower after the previous owner ripped a hanger bracket off of the mower deck while "bush hogging" with it. As far as I new the motor ran fine at that time. Fast forward approximately 3 years later and I have the mower. It hadn't been run during the 3 years. I welded on a new bracket and replaced a missing link and the drive belt (pricey). When I went to start it up the first trouble started but the mower didn't. I put a carb kit into it and the mower will now start reliably cold. It will not start when hot. Last time this happened I put a spare plug on the plug wire and grounded it on the engine block. I did not see a spark. The battery had 12.77 V at this time but the mower cranked slow like a dead battery.

When cutting I managed to high center the mower and remembered I hadn't aired up the dry rotted tires so I went back to do this and the mower cut due to the set safety switch, I wasn't fast enough. I took less than a minute to get the air hose and when I turned back to the mower it had belched oil all over. This is a mystery to me. What caused this? I did note the dipstick was loose, pretty sure it had been ok.

The last issue is the pto switch s not engaging the blades. The pto switch, and the ignition switch, check out with a meter. On one of the first few starts the electric clutch had jumped off of its limit hook and tore the wire harness loose. I replaced the wires and get nothing. I checked the electric clutch with a separate 12v supply and it does engage. I bypassed the pto and was able to mow a little before the issue mentioned above.

I was able to check voltage while cranking and it dropped to ~6V.

I suspect the battery is on its last legs because after 1 maybe 2 failed start attempts it needs recharging. It is a 360 CCA battery.
I suspect the alternator or regulator may be bad but not sure how to test that.
I also wonder if the electric clutch is bad.

Sorry for the long post, trying to get as many details out as I can.

I'd appreciate any help I can get with this. The mower is 52 inch cut and moves good when running. My back up is an old semi reliable 20" push mower. :(
Model 917.28858 Engine B1P677 1373 BL 090914ZD Carb Nikki 795969 266 2224 5B A31

Thank you,
Bruce
 

Rivets

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First the engine numbers are 31P677-1373-G1. From your description I suspect you have multiple problems and this is what I would be looking at. 1. Bad battery and would replace. 2. PTO wires may be switch when you retired the plug or clutch is bad. Without the engine running, but switch turned to the run position, unplug the clutch and engage the PTO switch. Test to see if you have 12V at the plug. If you do try switching the wires at the plug. 3. You have a hot short or open when the coil gets hot from sitting, can happen within 30 seconds. Next time it will not start after running, check for spark. No spark I would be replacing the coil. 4. Carefully watch your oil level, especially at cold startup. If you see the oil level rise I suspect the float needle is not seating and fuel is draining into the crankcase. Time to tear down and check the carb, maybe even rebuild again. Plus you will have to change the oil and filter again. Reply back with what you found and if you have any more questions.
 

BruceTX

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Hello Rivets,
Thanks for the reply! Took a bit of time to get back to it. I swapped the battery with another. I was going to swap the coil not thinking there are 2, I have 1 spare on hand. Instead I tested for spark and both cylinders had spark, so I figured let’s see what it will do. I have to direct wire the blade clutch for it to work but I was off and running. Got the front done no issues and made 1 pass a cross the back and it cut out. I checked for spark again and both sides were good. Battery voltage was 12.33 dropping To ~9.55 while cranking. It wouldn’t start. Thought about gas and added more but still wouldn’t start. Battery is now low. I expect it will start tomorrow if I can get to it.

Not sure what’s going on here any help you can offer is much appreciated!

Thanks,
Bruce
 

slomo

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If any battery, drops below 10.5 VDC while cranking, it's bad. Or you have corroded grounds, poor cables/connectors and such.

Charge the battery.

Check your main ground off the battery. Think hospital clean down to bare metal. Do a voltage drop test on the + and - sides of the battery, down each cable path while cranking.

Verify charging system is putting out over 13 VDC.

slomo
 
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