Briggs Engine Woes Cont'd

[donb1963]

I've posted several items on here about the 15.5HP OHV engine I'm working on for my in-laws. I did a leak test on it tonight and found air coming out of the exhaust which indicated a problem in the exhaust valve. After pulling the head, I found that the exhaust valve seat had come loose from the head and was sitting at a 45 degree angle in the head were it is supposed to be installed. This kept the valve from seating. The seat looks to be in tact, I didn't remove the valve to check it yet.

Can I buy a seat from Briggs or are they built into the head? I just looked at a schematic and don't see a seat sold seperately. Also, is this something I can replace myself or does it have to be pressed in by a machinist?

 

[ILENGINE]

The seat is not available as a separate item on the ohv engines. You may be able to get the seat back into its recess and pein it into place.

 

[tinmanpan]

Does your motor have an aluminum head? My Intek engine has done this twice already. I was told by a dealer that when the head gets hot it expands and allows the seat to slip out. If it is a briggs and stratton motor this is an ongoing problem and the dealer said to replace the motor with one that does not have an aluminum head. I have been waiting 5 days now to hear from briggs.

 

[ILENGINE]

Briggs hasn't used anything but an aluminum head in years. The main cause of briggs head failure is lack of air flow over the head due to clogged cooling fines. causes valve seats to come out, heads to warp, and valve guides to move and hold valves open.

 

[KennyV]

ILENGINE is right... air cooled engines need to have a lot of air flow to shed the heat.

A few other things that will contribute to exhaust valve woes: Running a poor grade of fuel, carburetor set too lean,intake leak or engine timing slightly off... any of these will also cause enough over heating to result in troubles... KennyV

 

[donb1963]

Many thanks to everyone who reposnded and gave me pointers... I got the seat back in (took to my expert lawnmower shop for a small fee) and then I was able to get it all back together. After getting the valves initially adjusted, it ran good for 15 minutes and quit. I found later that the intake rocker arm didn't get tightened completely ( my fault obviously). Once I re-adjusted and tightened the rocker arm, it runs great...

Everything I'm learning about these lawnmowers and my Ford 8N tractor, I'm picking up from forums such as this on the internet. Thanks again to everyone who gave me feedback/input on what to look for and how to get it fixed...