18 HP Briggs Valve Clatter at Idle

[Bill D 1,619]

I have an 18 HP Briggs twin from an 83 GT1800.  While it runs well at full throttle it sounds terrible at idle.  Lots of valve clatter. Is this normal for this engine?  I saw a post once where someone else said they had one that did the same thing.  What is the likelihood that the pin holding the crankshaft timing gear to the crankshaft is worn?  I saw a YouTube video showing this.  Just trying to figure out if I should run it as is, send it out for a rebuild or find a different engine. Thanks for the input as always.  Bill

[johnnymag3 2,447]

I’m not too sure myself Bill I don’t know anyone that does small engines as far as rebuilding anymore. Locally here you may want to just swap it out with something.

[Bill D 1,619]

2 minutes ago, johnnymag3 said:

I’m not too sure myself Bill I don’t know anyone that does small engines as far as rebuilding anymore. Locally here you may want to just swap it out with something.

I think Aldo's machine shop in Highland does small engines and there's a guy on my job that does them.  He did the head on my Jeep.

[gwest_ca-(File Mod) 10,509]

Can the valves be adjusted?

 

[Wayne0 299]

Can you adjust the valves on these? Curious as I have one. It sounds fine though.

Edited March 25 by Wayne0

[RED-Z06 2,128]

Pretty sure you have to cut the valve and seat to tighten the lash.  These were notorious for getting carbon on the heads and pistons, made them knock at low speeds 

[lynnmor 6,802]

17 minutes ago, RED-Z06 said:

Pretty sure you have to cut the valve and seat to tighten the lash.  These were notorious for getting carbon on the heads and pistons, made them knock at low speeds 

Is this one of the B&S engines that had pushrod bending problems?

[RED-Z06 2,128]

2 minutes ago, lynnmor said:

Is this one of the B&S engines that had pushrod bending problems?

This should be a Flathead opposed twin 

[kpinnc 10,819]

1 hour ago, lynnmor said:

Is this one of the B&S engines that had pushrod bending problems?

 

That's a v-twin issue, typically when someone mixes up the intake vs. exhaust rods. Intake is aluminum, exhaust is steel. 

 

Or if a valve sticks from long term sitting... Sounds like a hammer drill. Ask me how I know...

Edited March 26 by kpinnc

[Fordiesel69 219]

Most of the clatter is the plain bearings that the crankshaft goes thru.  They will usually run along time until you get a nest in the fins and overheat, or until a valve seat pops out (kinda like the onans).  

[Bill D 1,619]

14 hours ago, Fordiesel69 said:

Most of the clatter is the plain bearings that the crankshaft goes thru.  They will usually run along time until you get a nest in the fins and overheat, or until a valve seat pops out (kinda like the onans).  

This engine has a ball bearing supported crankshaft.  It may have been overheated as there was a lot mouse nests in the fins.  Plugs looked good though.   Really sounds like valves.  I've got a couple of leads on replacement engines.  Not sure this one is worth putting money in.

[Fordiesel69 219]

You are correct, I keep forgetting that most of the factory 16HP twins in the GT-1600 / GT-1642 have the plain bearings and the 18HP used in GT-1800 / GT-1848 had the ball bearing.  

If it runs good but has a clatter it may still last a decent amount of time.   

[Bill D 1,619]

I guess I'll have to figure out the cause of the noise first before I can decide if I want to run it as is.  I do remember someone on here saying they had a Briggs and it had a similar valve clatter.

[Fordiesel69 219]

Can you stand back a bit from the engine and make a quick 15 sec video and paste the link? 

 

 

[Bill D 1,619]

On 4/10/2024 at 3:02 PM, Fordiesel69 said:

Can you stand back a bit from the engine and make a quick 15 sec video and paste the link? 

 

 

Unfortunately, no.  Once I heard the noise I pulled it out in favor of an M14  I had.  However the M14 is pretty tired and I'd like to put the Briggs back in.  Whether it's this one or another remains to be seen.