Excessive exhause valve clearance Briggs

[wolfden793]

Hi All,
Ran across a problem with a Briggs 3.5 HP 90000 series motor. Doing a complete rebuild and had to put in a new exhaust valve, but after lapping it seems to "ride" up above the block a bit and has excessive clearance way in excess of recommended specs. I was thinking the seat may have to be ground? Intake OK, but not exhaust. Thanks in advance for any help!

 

[Leejohn]

Grind a little off the valve stem.

 

[wolfden793]

Hi!

Thanks for your message. I think my post wasn't as clear as it should have been. The gap between the end of the valve stem and the valve tappet is supposed to be about .008 and it's way in excess of that. You can see the gap with the naked eye, and the top of the valve is riding above the block slightly. That's why I thought perhaps cutting the seat would work? Thanks!

 

[denchen]

It sounds as if the valve seat has not been ground to the full spec at manufacture. An engine machine workshop will have a small machine where the seat is ground whilst the valve is rotated. Not a DIY workshop tool, but about a two minute job with the right machine.

 

[wolfden793]

Thank you very much for your message. I have a shop locally that can do this. I appreciate your time!

 

[mark02tj]

It sounds as if the valve seat has not been ground to the full spec at manufacture. An engine machine workshop will have a small machine where the seat is ground whilst the valve is rotated. Not a DIY workshop tool, but about a two minute job with the right machine.

Not necessarily true. Somewhere in my toolbox I have a valve seat cutter tool. Used it many times when I was repairing small engines back in my college days. Look around and you might be able to find a cutting set on the web. Or, take the engine to a small engine shop and see if they'll cut the seat for you.

 

[wolfden793]

Hi!!

I actually did both! I found a good, used cutter set online and took the engine to a local machine shop in the meantime. Thanks for your reply!

 

[Richard001]

Hi!!

I actually did both! I found a good, used cutter set online and took the engine to a local machine shop in the meantime. Thanks for your reply!

So do you have the engine back from the shop yet?

Are you sure that the problem is not that the valve seat has moved up from it's original position ? Happens a lot on flat head engines.


Richard

 

[wolfden793]

Hi Richard,

Thanks for the comment. No, not yet but expected tomorrow. Never really considered the movement of the seat, but my guy will know and pass it along.