My 12 hp. kohler was burning almost as much oil as gas

So, I orderred a rebuild kit. Included is a new set a valves. When I pulled
the old valves, I see a burnt spot on the casting where the valve sealed.
How should I machine this out? I've heard of putting lapping compound under
the old valve and twisting. Seems like this might take forever.

Any suggestions?

Karl

"Karl Townsend" remove .NOT wrote in
message ink.net...
My 12 hp. kohler was burning almost as much oil as gas

So, I orderred a rebuild kit. Included is a new set a valves. When I
pulled the old valves, I see a burnt spot on the casting where the valve
sealed. How should I machine this out? I've heard of putting lapping
compound under the old valve and twisting. Seems like this might take
forever.

Any suggestions?

Karl



i would suggest putting an angle stone in a hand drill and cuttin the valve
seat to remove the bad spot...if it is not too deep.Then lap in the NEW
valve with lapping compound.

Most engine repair facilities can bore and install a valve seat insert.
Walt
"digitalmaster" wrote in message
...

"Karl Townsend" remove .NOT wrote in
message ink.net...
My 12 hp. kohler was burning almost as much oil as gas

So, I orderred a rebuild kit. Included is a new set a valves. When I
pulled the old valves, I see a burnt spot on the casting where the valve
sealed. How should I machine this out? I've heard of putting lapping
compound under the old valve and twisting. Seems like this might take
forever.

Any suggestions?

Karl



i would suggest putting an angle stone in a hand drill and cuttin the
valve seat to remove the bad spot...if it is not too deep.Then lap in the
NEW valve with lapping compound.

On Sun, 19 Mar 2006 21:16:11 GMT, "Karl Townsend"
remove .NOT wrote:

My 12 hp. kohler was burning almost as much oil as gas

So, I orderred a rebuild kit. Included is a new set a valves. When I pulled
the old valves, I see a burnt spot on the casting where the valve sealed.
How should I machine this out? I've heard of putting lapping compound under
the old valve and twisting. Seems like this might take forever.

Any suggestions?

The right way is with a valve seat grinder or reamer and then lap
the new valves in place. You could make up a crude tool using a small
grinding wheel the do the job but for a one off it's not real
economical. It would be better if you took it to someone with the
right tools and let them do it. It shouldn't cost to much with the
block already stripped.

If you're determined to do it then let me know and I'll see what I
can do to describe the tool needed.

"Karl Townsend" remove .NOT wrote:

My 12 hp. kohler was burning almost as much oil as gas

So, I orderred a rebuild kit. Included is a new set a valves. When I pulled
the old valves, I see a burnt spot on the casting where the valve sealed.

This doesn't increase oil consumption. Did you replace the valave guides
and the sealing ring on top of the guide? Is the guide still to specs?
Are the rings OK?
And, when you pulled the valve, you might have ruined the guide finally.
Did you remove any burr on the top end of the valve?


How should I machine this out? I've heard of putting lapping compound under
the old valve and twisting. Seems like this might take forever.

It depends on how deep the spot is. The lapping paste comes in coarse
and fine. And it works quite good and fast. But you might consider going
to a shop and let "mill" the seat to specs. Don't know your mfgs, but
here, it is Hunger making the necessary tools. For a single job, it's
not worth spending the money.
You could make a (hand operated) reamer, but also, the time isn't worth
the few bugs you would have to spend if you let it do.


Nick

--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO // Eigenbau-Digitalanzeige
http://www.yadro.de

digitalmaster wrote:

i would suggest putting an angle stone in a hand drill and cuttin the valve
seat to remove the bad spot...if it is not too deep.Then lap in the NEW
valve with lapping compound.

It is much quicker, if you do that with a cold chisel and a sledge
hammer!
I don't reccomend both ways.


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO // Eigenbau-Digitalanzeige
http://www.yadro.de

....
If you're determined to do it then let me know and I'll see what I
can do to describe the tool needed.

Yes, please. (If I was totally worried about econimics, I never would have
bought a machine shop)

Karl

Some shops use a carbide cutter to cut the seats instead of a stone. Suppose
if you wanted to make your on cutter and attached a carbide bit to it you
could cut your seat. Could index a carbide cutter and put it in the mill.
Cut dead slow.

Be sure and check your valve clearances after seating your valves.

On Sun, 19 Mar 2006 21:16:11 GMT, "Karl Townsend"
remove .NOT wrote:

My 12 hp. kohler was burning almost as much oil as gas

So, I orderred a rebuild kit. Included is a new set a valves. When I pulled
the old valves, I see a burnt spot on the casting where the valve sealed.
How should I machine this out? I've heard of putting lapping compound under
the old valve and twisting. Seems like this might take forever.

Any suggestions?

Karl


Greetings Karl,
There is more than one tool made for this job. A popular one is a
cutter with a pilot. Kohler uses, or at least used to use, a three
angle valve seat. The first angle is 30 degrees from horizontal, the
next is 45, and the last 60. The middle seat width is .037 to .045
wide. The piloted cutters and grinders will not work well if the guide
is worn. After the seat is properly ground then a new valve can be
lapped to the seat. You can lap the seat with a valve to remove the
burnt spot. But what will happen is the valve will seal well when cold
but when hot will move away from the perfect seat. So the lapping
should only be done to just make sure the valve and seat are round and
contacting evenly. The above is from a book I've used to repair many
small engines. I have, when feeling particularly cheap, just used old
valves to lap on the seat and then used new or properly re-ground
valves with just slight lapping. When I have done this here is the
method: Clean the tops of an intake and exhaust valve. Glue these
cleaned surfaces to each other with super glue. Put a pin in a VSR
drill motor that has a diameter close to that of the valve stem. Put a
rubber hose over the valve stem and pin. Use lapping compound between
the valve and seat. Don't run the drill too fast and reverse direction
often. This works fast but the results are not the best. Still, I have
had engines run well for many hours after using this method of sloppy
repair. If you only have the original valves from the engine to work
with a sharp rap will separate the valves and they can then be ground
in the lathe. Then slightly lapped in the seats.
ERS

On Mon, 20 Mar 2006 01:41:32 GMT, "Karl Townsend"
remove .NOT wrote:


...
If you're determined to do it then let me know and I'll see what I
can do to describe the tool needed.

Yes, please. (If I was totally worried about econimics, I never would have
bought a machine shop)


I figured. If we where closer I'd do them for free.

Ok. The official valve "grinding" tools use a pilot that fits tight in
the valve guide. Most are tapered (very slightly as in .005" over the
length) to wedge in but some are split like a expanding collet. This
pilot has a standard dia that sticks out above the seat. This is what
the grinding arbor runs on. The arbor in a good set will actually have
ball or similar bearings to run on the pilot but cheaper ones just use
a bushing. The grinding wheels usually screw onto the end of the
arbor. The arbor is drove by a high speed tool through some flexible
means (the one I have used a large ball end hex on the right angle
type drill tool). I know of one company making adapters to use die
grinders for driving the stones.

The more modern way is with a carbide valve seat cutter. These use a
cutter with inserts on a arbor. A pic of one is on this page.

http://www.mfgsupply.com/SmEngToolsValve.html

I have in the past used a home made arbor where the arbor was one
piece and the stone screwed on it. This arbor turned in the guides and
you just chucked a drill onto the end of it. This is not as good a
method since clearance is needed on the arbor and valve guide and it
wears the guide and you're grinding. But it's the simplest method I've
seen.

As for cutting the seats you need to keep in mind that the seat
width is specified. Thus any grinding of old seats will call for
narrowing the seat width after grinding with the right angle stone for
the valves. This is done with both a steeper and flatter angled
stones. Example is for a 45 deg seat you grind with the 45 deg stone.
Then use a 30 deg and a 80 deg stone to narrow the seat and get it to
the right width and diameter (close to the middle or more toward the
inside of the new valves sealing surface is about right).