Briggs (JD LA125) engine sounds different after head gasket

[WyattEarp]

I have a John Deere la125 with a Briggs and Stratton 21 hp engine. Unfortunately after only 100 hours with scheduled maintenances performed, the head gasket failed. The Mower started burning oil and you could hear and see smoke from a drip of oil into the combustion chamber.

I decided after doing research it was a job I'd tackle myself to learn about the engine and save cash. After I was done - the moment of truth... Fire it up! I immediately noticed the mower was quite a bit louder than before. It wasn't smoking any more, so I decided I'd give it a go and see what happens. If it blows I'll buy a Honda! 

I've now been mowing with it for the past year in extremely tough conditions and it runs like a champ, just louder. I have a YouTube video showing 15 seconds before changing the gasket ( you can see puffs of smoke ), and 15 seconds after the change.

My question is: did I set the valve lash too tight maybe... Or too loose? I forget the feeler gauge clearances I used but .005 and .007 ring a bell. I can look it up for sure.

Here's a link to the video:
http://youtu.be/i0uJeZu3hT0

Thanks in advance

 

[bertsmobile1]

Not uncommon for this to happen.
Without the leaking gasket you are getting more bang from every engine fire.
More bang = more noise.
You might like to check for leaks around the headder pipes.
And finally, it is not a crime to replace the muffler.
Contry to popular belief they do wear out.

 

[WyattEarp]

I appreciate your quick response.

I was used to the noise level prior to the head gasket failing and remember being shocked when I heard the difference in noise levels. The videos don't really do show the decibel increase. I mow with earmuffs now ?

At first I thought maybe I bent a valve(s), but after as much mowing as I've done I don't think that's the case.

Could the valve lash cause a change like this? I'm not an experienced Motorhead, so maybe you're right!

 

[WyattEarp]

I know this is an old thread, but I resolved the problem.

I went to my local JD shop and played the video for their manager and one of the techs. They printed some service manual pages for me and I finally had time to give it a go.

Their service manual basically said to move the piston past TDC 1/4" and set the valve clearances. .003 - .005" for intake and .005 - .007" for exhaust (I believe). I did what the manual said, put everything back together, filled with oil / new filter, changed plug, fired it up and it sounded as bad as before, ran for 10 seconds then died and wouldn't start again.

I drained the oil, took the valve cover back off and the intake valve cap was sitting in the bottom of the valve cover. Well that's not good...

After doing a lot more reading I found my problem on another thread. I read so many threads and watched so many videos - but there's one minor detail often left out even from the JD manual...(maybe it's common knowledge, but I'd think it's an important detail to put in a manual). The piston needs to be at 1/4" past TDC on the compression stroke when you set the valve clearances to the factory specs. So, spin the flywheel until you see the intake push rod push the intake valve open, then back down and the valve closes. Now you're on the compression stroke, so bring the piston up to TDC and go 1/4" back down towards it's bottom position. Now set the valve clearances.

I fired my mower up this morning and it sounds great....quiet again finally.

Hopefully this help someone down the road.

 

[reynoldston]

Yes that is common knowledge TDC is when the spark ignites the fuel under compression with some timing involved. They write the service manuals more for the repair shops then the home owner. I find that most mechanics use the manuals more for specs that anything else.