Ariens Sierra 1440H starts hard and runs rough...

mtb54703April 10, 2014

Hi all,

I have an Ariens Sierra 1440H lawn tractor that is hard starting and runs rough. I just completed replacing the both gears on the electric starter so I had to pull the fly wheel. After I got everything back together it started and ran fine. I let it run for a few minutes and then turned it off. I then decided to figure out which indicator lights went in which holes on the dash - two of them were laying loose on top of the battery. I was doing short start/stop cycles (choke off) on the engine while observing which light turn on/off when after about 6 cycles it started to idle very rough and stop on it own. My guess was that it was flooded so I let it sit for a bit. That was yesterday evening. Tonight I gave it a try again and it didn't run any better. So I pulled the spark plug and it looked okay - gapped okay too at 0.030". Filter and pre-filter were clean. Fuel filter was replaced last year (as was the air). I tried a new plug, no difference. I put the old one back in. In the video here:

the first start was with the choke on, then I back it off. It started and but is not sounding like it should (although it doesn't sound that rough in the video, it is).

If I had more than on cyclinder I would think one was missing.

The engine is a B&S 29P777-0644 A1

The flywheel is keyed to the shaft so I don't think it possible to put it back together wrong. I did have to drill out the rivets to replace the gear ring, and I thought I clean up the metal shavings completely if any leftovers on that could be the cause of the problem.

Any suggestions?

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Well, it is possible to under torque the flywheel and now the key has sheared. Somehow, the model of the engine does not seem right. From the ring gear comment, a 28P777? The good word is on most Briggs you can remove the flywheel bolt and verify the key is intact or not. If it is a 28P777, use the steel key P/N 796335 and torque to 110 ft pounds. or go old school and use the standard aluminum key at 100 ft pounds.

    Bookmark   April 10, 2014 at 11:07PM
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There is only one correct procedure to use when putting the flywheel back in place on the crankshaft.
You must make sure every surface of the crankshaft and the flywheel meet each other is completely clean and oil/grease free.
No lube of any kind. Then you set the flywheel onto the crankshaft and align the keyways of each. Lastly, you push the key down into the aligned keyways slot, maybe having to lightly tap the key to get it down flush with the top surface of the flywheel. Then you put on the nut/bolt and torque it to specs, using a torque wrench.
Skipping or substituting anything in that procedure can result in a sheared key.

    Bookmark   April 11, 2014 at 1:21AM
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Thanks for the suggestions.

The model number is a 28P777.

I'll pull it apart and check the key - it was an aluminium key.

    Bookmark   April 11, 2014 at 9:32AM
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Sheared key it was - obviously from incorrect installation. The very first time I was reinstalling the flywheel I was having difficulty getting the key back in so I stuck the key in the slot on the shaft and then lowered the flywheel onto the shaft. I also did not tighten the bolt enough because I was took it off the second time it was not nearly as tight as the first time.

$2.74 and it runs great now.

Thanks for the help.

This post was edited by mtb54703 on Sat, Apr 12, 14 at 10:53

    Bookmark   April 12, 2014 at 10:52AM
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Most all key failures on engines that have belt driven blades can be attributed to either improper installation techniques, or a hydrolock situation being present in the engine.
The hydrolock situation is probably the least likely scenario, because the starters themselves are simply too weak to really overpower the key all by themselves.
The secret to a key staying intact is good, clean, oil free surfaces on both tapers, ......installing the key at the correct step in the process, and proper torque of the retention fastener.

    Bookmark   April 12, 2014 at 1:16PM
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