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first time out,thrown rod?


wwc's Avatar
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04-16-09, 06:49 PM   #1  
first time out,thrown rod?

I have a old small John Deere riding mower, it has a 3 1/2 brigs engine pull start.

I replaced the top section that holds the rope because the last one broke last fall.
it started up fine and was mowing ok but seemed like the engine wasn't running very fast, i got out to check the engine idle screw and it died, no noise ,no bangs.
Now when i pull on the rope to crank the engine over it just turns and doesn't turn the engine over, the center part of the engine where the rope wheel covers that part ( crank shaft i think ) just spins with the pull of the rope.

what is wrong?

is the crank shaft broke or a rod broke? what can i do?

 
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04-16-09, 07:19 PM   #2  
First choice would be the flywheel key = not a hard fix. Just pull off the cowling under the rope pull and see if the flywheel is spinning without turning the center nut that holds it on. The key is between the flywheel and the crank under the nut.

 
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04-16-09, 10:10 PM   #3  
If the shaft with the blade is turning, the rod is broken. Was it out of oil?


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04-17-09, 02:48 AM   #4  
just changed oil and it is full.

So do i need to pull the flywheel off the engine to get at the key?

I know the end of the shaft that comes up into the plastic rope wheel moves freely and the flywheel and screen doesn't move.

I'll try and get at it today.

 
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04-17-09, 03:52 AM   #5  
If I'm understanding everything correctly, the flywheel is spinning on the shaft that goes through the center of the flywheel. The key on that shaft (being the end of the crankshaft), aligns the flywheel on the crankshaft.

Hopefully that is the only problem.

Just pull the flywheel. If it's spinning freely that won't be hard. When you put everything back together make sure you torque the flywheel nut back down tightly. If the flywheel is loose, something must have come loose there.

 
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04-17-09, 04:47 PM   #6  
update

Ok today took the top off and in the process found a spring laying beside the engine so thinking it must go on top of the crank shaft cover i placed it on top and slid the cover back on.
pulled the rope and it fired up.
the rope did not self wind back up though and a second later it started a high pitch squeeling and i shut it off, looked at everything i figurted maybe the rope pulley wasn't going back up so i wound the rope back up by hand by turning the pulley from under the cover and got a screw driver, then pulled rope again and it fired right up but the squeeling came back so i carefully pried up on the pulley and the noise stopped and the rope still did not wind back up, and i noticed the crank shaft pulley kinda trys to wind back up but won't.
Now what does that mean and what do i do next ?

 
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04-17-09, 05:18 PM   #7  
The squealing is the starter clutch. Sometimes you can buy a little time by squirting an aersol lubricant around the center of the screen but the best ploy is to remove the housing then the screen. Hold the flywheel with a strap wrench, don't stick a screwdriver through the fins, and remove the clutch with a pipe wrench,turning ccw. Polish the end of the shaft with fine grit sandpaper and install a new clutch p/n 399671. Make sure it is tight.

 
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04-17-09, 06:32 PM   #8  
would that make the rope not rewind by it's self also ?

 
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04-17-09, 09:03 PM   #9  
Yes, that would cause it. Apparently the crankshaft wasn't turning then, when you posted the first post? Glad the engine isn't blown!


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04-18-09, 02:57 AM   #10  
yes thankfully the engine isn't blown, when i saw the center portion of the clutch turning i thought that was the crankshaft end, not realizing there was a clutch over the shaft.
I'm going to try and find someone around here to buy another clutch today.

one more question, is there supposed to be a spring on top of the clutch shaft into the starter pulley hole that it connects to. i was just guessing it went there.

 
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04-18-09, 10:43 PM   #11  
Yes, it should go in the hole between the rope pulley and the engine shroud. If yours came out, the pulley may be worn. It should have a plastic button on the end of the spring. It's ok to just leave that spring out...most weren't equipped with them anyway.


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04-19-09, 02:43 AM   #12  
thanks, i have to wait till monday to get a new clutch but i'll try then.

 
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04-20-09, 05:44 PM   #13  
update

Ok installed the new starter clutch and a new spark plug.

one pull and it started up and ran great no screaming.

BUT the cord doesn't self wind back up, what gives?

I replaced the old rewinder with part number 390391, which is a whole new top with the cord already wound up and installed.

Now what do i do?

 
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04-20-09, 08:59 PM   #14  
Sounds like the spring came unwound.


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04-21-09, 06:59 PM   #15  
Thats what i thought too, i took the top off and it wound up fine by itself, so i removed the spring from on top of the starter clutch and remounted the cap and rope assemble and it started up great and re wound just like it should.
So hopefully it's fixed, thanks for all the help guys.

 
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