What is this sound? (6.75hp B&S)

[natesi]

Hello,

I changed the oil in my mom's mower today -- along with sharpening the blade, new plug, and new air filter. When I was done I took it for a quick test and it ran and sounded great -- UNTIL I turned it off.

When the engine slows down it sounds like there's a bell inside (a "ting, ting, ting" sound).

I rarely use this mower so I don't know how long this noise has been happening.

In the video you can hear the sound as the engine slows down, after I turn it off.

Then I pull the cord numerous times just to turn the engine and reproduce the sound -- I intentionally don't have the start lever down when pulling on the cord -- to I prevent the mower from running. Because once it's running it sounds normal.

Is this thing on it's way out?

Thanks for all the help!

 

[ILENGINE]

I would make sure the blade is tight, but I suspect that noise is the engine brake against the flywheel. Could also be a sheet metal vibration induced by the engine braking. I don't think it is anything serious.

 

[StarTech]

It sounds like metal to metal contact. To see if it is related to the engine brake disconnect the spark plug wire, hold the OP lever down, and pull while listening. If noise goes away then it is the engine brake related; otherwise, I think it is a slight contact of the blade and the mower housing or crud at some point of the rotation which cant be heard while the engine is running.

 

[natesi]

Thanks guys -- here's the results of some more troubleshooting and your recommendations:

1 -- Blade is tight; I uninstalled and re-installed and torqued it to spec
2 -- There are no obstructions under the deck that the blade is hitting
3 -- I disconnected the sparkplug and held the handle down to disengage the brake and the same noise continued
4 -- I removed the blade and pulled on the engine start cord -- and the same sound was there.
5 -- Totally removed the spark plug and pulled on the engine start cord -- and the same sound was there

I don't know mower engines real well, but it sound like something is pinging against the top of the metal shield or something (under the plastic shield).

Further troubleshooting if this helps: I turned the crank by hand, in the CORRECT cutting direction, and you can hear the sound every so often. Please see the video below.

 

[Scrubcadet10]

remove the metal blower housing, 4 or 5 3/8" or 10mm bolts, two on the back, two on the front. take it off. spin it by hand (With the plug wire off of the spark plug for safety) if the noise goes away, the flywheel or starter cup is hitting it.

 

[natesi]

Thanks guys.

I removed the gas tank, oil filler, and blower housing and then spun the engine.

It ended up being a tiny piece of shield that was magnetically drawn to the flywheel, as it turned at a lower speed. See video.

I put everything back together and made sure that the little shield installed properly this time (two ears inside, and the middle tab on the outside of the blower housing).

Ran it when I was done and it sounded great!

Thanks for all the help!

Thanks!

 

[Scrubcadet10]

wow, never seen one do that before. glad you figured it out.

 

[heamicdan]

hmmmmmmmmmm learn something new every day

 

[Rivets]

A DIYer had the shroud off and did not install it properly. Have seen this more than once, they hate it when you bill then for their mistake.

 

[Ranamow]

I've seen that often, and have done it myself. When installing the starter housing, you have to align the tabs on the shroud. Just one of those things!