Briggs Valve Lash

Is the valve lash adjustable on a 5 hp Briggs L head engine?

How hard is it to replace the valve guide?

Mine just dropped the exhaust valve. The retainer end of the valve, as well as the stem are battered and worn. The retainer looks fine. I had to file the tappet end of the valve to get it out of the engine. It appears to be dead soft all the way down the stem. Tappet looks fine. Guide may be OK, but this valve has about .030 side play in it. Seat looks fine.

Anyway, the owners manual refers to a valve lash tolerance, and the generic Briggs L head repair manual.

Thanks in advance.

John

Re: Briggs Valve Lash

Having done this on a few motors I will just say get another motor. The dropped valve is likely only the tip of the iceberg and getting a new guide in, new seat and cutting a new valve to get proper lash is only the beginning.

The seat needs to be replaced (they are peened in) to get proper lash with a new valve, 90% of the time just replacing worn components will bring everything into spec. A new guide is a PITA but possible, just drill out and slide hammer out the old one and buy an oversize version from B&S or make your own out of red brass on a lathe.

I'm willing to bet that once you go through all that trouble you will find the pistons are worn out, the rods and crank are worn out and the mains are shot too. It may last another season or two but usually its a sign of death for the engine to drop the valve which means its not cost effective to repair.

Re: Briggs Valve Lash

4JawChuck said:

Having done this on a few motors I will just say get another motor. The dropped valve is likely only the tip of the iceberg and getting a new guide in, new seat and cutting a new valve to get proper lash is only the beginning.

The seat needs to be replaced (they are peened in) to get proper lash with a new valve, 90% of the time just replacing worn components will bring everything into spec. A new guide is a PITA but possible, just drill out and slide hammer out the old one and buy an oversize version from B&S or make your own out of red brass on a lathe.

I'm willing to bet that once you go through all that trouble you will find the pistons are worn out, the rods and crank are worn out and the mains are shot too. It may last another season or two but usually its a sign of death for the engine to drop the valve which means its not cost effective to repair.

Click to expand...

There isn't enough wear in the cylinder to take off the hone scratches. No ridge, not even much carbon. This engine has about 40 hours on it. What gets me is the tappet end of the valve is battered all out of wack, and the shaft on it appears to be worn 10 or 15 thou., but the tappet is smooth and nice, and even the spring keeper looks to be in new condition. I had to file the burr off the valve to get it out. The metal was pretty soft. I'm thinking the valve itself missed a hardening step in manufacture.

Back to the engine. I think you said that valve lash is adjusted by grinding metal off the tappet end of the valve. Can that be done without a lathe? A major small engine shop where i'd buy the parts is only a few miles from me. Perhaps I can get a valve, rough grind it to a few thou clearance, lap it in, measure the clearance, and take it back to them for the final grind. Should be about a 2 minute thing for them.

Maybe I should go get a Greyhound 6.5 engine on sale for $130 and slap it in.

Re: Briggs Valve Lash

You do grind the tappet end of the valve to get the proper clearance, you can do it yourself on a grinding wheel. Just go easy so as to not build up a lot of heat ruining the heat-treating.

Re: Briggs Valve Lash

Got a new valve. It's about 5 over zero for length. Seems to fit the guide OK, or at least as good as the intake valve. I think I'm just going to stick it in (after adjustment of course) and run it.

I think the old valve stem was soft and/or the keeper wasn't on it right.

Thanks for the help
John

Re: Briggs Valve Lash

The worst case scenario is you do all that work and some fine shavings end up in the sump and destroy the motor later, I've seen it happen.

Price out a short block, they aren't that expensive...I would hate for you to do all that work and have a wrecked engine 3 hours later.

http://www.gardenlawnmowers.info/454/parts-accessories/stratton-shortblock/

Re: Briggs Valve Lash

4JawChuck said:

The worst case scenario is you do all that work and some fine shavings end up in the sump and destroy the motor later, I've seen it happen.

Price out a short block, they aren't that expensive...I would hate for you to do all that work and have a wrecked engine 3 hours later.

http://www.gardenlawnmowers.info/454/parts-accessories/stratton-shortblock/

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Twenty bucks in parts and a couple of hours to fix it. If it runs the rest of the summer, that's OK.

Engine's 12 years old. Hasn't been run much. Doesn't burn oil. Only noise in it was this messed up valve.

New one slopped in. Likely to run a year or so. Then Frikken-Stratton is going into the metal bin and I'll put a greyhound on it. Almost Honda quality and performance for under Briggs price.

I got the valve ground to length and installed. That was a real chore without a valve spring compressor. I need to slap the rest of it together tonight before I forget where all the little springy thingies go.

Thanks again for the help.

Re: Briggs Valve Lash

Cool, I did a 5Hp Briggs years ago because it had a burnt exhaust valve and replaced all those parts you were looking at. I fabricated new bronze guides and even ported the exhaust and intake, a custom 80cc dirt bike muffler was the final topper to a SS exhaust pipe (hey I was young and bored and a first level apprentice!).

I had the coolest quietest lawnmower on the block although it likely put out only 5.1 HP...but it was custom and I built the entire thing. I sold it at a garage sale for $50 which was $50 more than I paid for it, fun to play with and cheap and simple.

Still for the time and money I was told I could have gotten a new short block for 1/4 I paid for the parts to fix it and have a new motor, kinda kicked myself afterwards...my time is still worth money.

Good luck with your repair.

Re: Briggs Valve Lash

4JawChuck said:

Cool, I did a 5Hp Briggs years ago because it had a burnt exhaust valve and replaced all those parts you were looking at. I fabricated new bronze guides and even ported the exhaust and intake, a custom 80cc dirt bike muffler was the final topper to a SS exhaust pipe (hey I was young and bored and a first level apprentice!).

I had the coolest quietest lawnmower on the block although it likely put out only 5.1 HP...but it was custom and I built the entire thing. I sold it at a garage sale for $50 which was $50 more than I paid for it, fun to play with and cheap and simple.

Still for the time and money I was told I could have gotten a new short block for 1/4 I paid for the parts to fix it and have a new motor, kinda kicked myself afterwards...my time is still worth money.

Good luck with your repair.

Click to expand...

But the satisfaction............PRICELESS.

Re: Briggs Valve Lash

Got it all back together. It starts and runs. No unusual noises. I'll throw it back on the splitter tomorrow afternoon and resume my exercise program.