Briggs Stratton valve seat

jokers · Nov 12, 2009

I have this little 5 hp Briggs engine on a logsplitter that has lasted surprisingly longer than I ever expected it to and keeps on running well for the most part, but it has developed this odd problem of the valve seat under the intake valve walking out and holding the valve open for a complete loss of compression.

Obviously it won"t run like this so I pop the head off, ever so gently tap the valve face to drive the seat back in, put the head et al back on, and away we go!

This has happened twice now with the interval between occurences somewhere around 15 hours of run time, not necessarily working time as I do typically let the engine run as I putz around moving wood to be split and so forth.

My question is, has anyone else experienced this failure and is there a more permanent fix? How about red Locktite underneath the seat? Is this failure symptomatic of something that I"m doing wrong?

Thanks in advance for feedback and advice.

Anonymous-0 · Nov 12, 2009

I've taken a centerpunch and run some dots around the perimeter to tighten up the seat before, but it's usually a short lived fix.

scott mcintosh · Nov 12, 2009

Take center punch and peen block around valve seat then you will have to check valve clearance.Scott

44 massey · Nov 12, 2009

I know most machine shop use locktite when installing new seats so might be worth a try! There are several different types of locktite so check it out for application.

Joe (Wa) · Nov 12, 2009

.
http://www.repairspot.com/loose_valve_seats.html

jokers · Nov 12, 2009

To everyone who has replied and especially to Joe for that great pictorial!

Joe (Wa) · Nov 13, 2009

A valve insert is an interference fit, meaning that the insert is a couple thousands larger diameter than the bore it is pressed into. So if it is popping out due to thermal growth of the bore and you have to tap it to reinstall it can be staked as shown and you probably won't need a cutter or grind.

Tap in the insert, install the valve and turn the engine a few revs to work the valve. Very light center punch 3 places first pass, and 2 gradually deeper passes same places. If you do not have the edge that is rolled over in the last pic, center punch 3 more places as above.

Prussian blue & lap as required.

JDemaris · Nov 13, 2009

There is no cost-effective good fix for it. Briggs & Stratton had that problem on several engines. Usually the worst on the 8 horse and 10 horse engines.

The combination of an aluminum block and being air cooled and very hot running makes the need for that seat to be a very tight fit.

The only long-term fix is an oversize seat, new bore cut and then you have to freeze that seat in something like liquid nitrogen. You can't just press it in since the block is aluminum and the soft metal will just displace when you try to press in a room-temperature seat.

When I worked for a Briggs dealer, they'd authorize some repairs on larger engines. Smaller ones if under warranty usually just got thrown out and new short blocks installed.

And yeah, you can just take a center-punch and hammer the aluminum around the seat and you might get a few more hours out of it.

To fix it right will cost more then the cost of an engine.

Kentb of SWMO · Nov 14, 2009

The center punching around the valve set is shown in Briggs repair manuals.

Kent

Briggs Stratton valve seat

jokers

Member

Anonymous-0

Well-known Member

scott mcintosh

Member

44 massey

Member

Joe (Wa)

Well-known Member

jokers

Member

Joe (Wa)

Well-known Member

JDemaris

Well-known Member

Kentb of SWMO

Well-known Member

Similar threads