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Discovered that the intake valve seat was sitting wonky when I went to replace the head gasket.

Now that it's in place & I've lapped both valves it appears that the Intake Valve clearance is at .006 (upper limit is .005) and no clearance on the Exhaust Valve (lower end should be no less than .005).

This is with piston 1/4 down from TDC following compression stroke.

When I was trying to match the seating visually of the Intake to the existing seating of the Exhaust I may have seated it too well ... I can barely fit a fingernail between the meeting surface of the seat and intake valve opening.

Before I take anything off the end of the exhaust valve stem Question: should there be a "step down" from the Exhaust seat to the exhaust valve opening? It is not flush. It makes me wonder if the seat is pushed in too far.

If that is the case how do I safely unseat the Exhaust seat without damaging the surrounding aluminum?

Thoughts?

[Sorry … the included pics with inserted text are basically useless since the quality got degraded in the upload.]

If I understand your question, the exhaust valve seat looks ok, it is the intake that is your problem.

This guy does a rough valve service, I don't know why he doesn't re-cut the seats though. Those get cocked in the bore and just lapping the valves is insufficient.

The valve seats are recesses that have a stop lip so they can't inserted too deep. The intake seat once reseated must be staked in place.

And your valve clearance specs seems off but I don't see the engine numbers posted so I can't look them up.

But normally most L-Heads have the following valve clearances. ANd I always shoot for the larger clearance as L-Head tends to close up the gaps over time.

But your problem is the intake valve seat is not fully seated in the recess, and the ability of curing it is likely not feasible on such an old engine.

Engine: 28M707

Let’s try this again. Clearly I confused you.

Intake Valve Clearance should be
.003 - .005 it’s at .006, if not .007

Exhaust Valve Clearance should be
.005 - .007, it’s at 0

I have reseated the Intake Seat, seems pressed in all the way.

Exhaust seat, that I haven’t touched looks like it is pressed in too far. It does not seemed to be up against a lip. When I feel it it’s not butting up against anything.

So how do I dislodge the Exhaust Seat without damaging it.

Do I? That’s what seems best.

Or do I just leave it as is, it’s been lapped & take off some from end of valve stem to create needed clearance?

Fish said:

This guy does a rough valve service, I don't know why he doesn't re-cut the seats though. Those get cocked in the bore and just lapping the valves is insufficient.

Click to expand...

Thanks for you attempt to help me ... I love this guy ... his videos have helped me a lot.

Hmmm still not giving all the engine info but I took a look at 1 of 200+ 28M707 and here is it valve clearances for the L-head.



The valve clearances you are quoting are for an OHV engine not a L-head.

Now if can pick which of the following is your engine would help looking it up.

StarTech said:

Hmmm still not giving all the engine info but I took a look at 1 of 200+ 28M707 and here is it valve clearances for the L-head.

View attachment 67021

The valve clearances you are quoting are for an OHV engine not a L-head.

Now if can pick which of the following is your engine would help looking it up.
View attachment 67022

Click to expand...

Apologies once again:
28M707-1162-E1 Code: 980325ZA

To remove seat...run a bit of mig or stick weld around the inner diameter. It will shrink and fall out. Of course you need a new replacement then

Adevo said:

Apologies once again:
28M707-1162-E1 Code: 980325ZA

Click to expand...

StarTech said:

Hmmm still not giving all the engine info but I took a look at 1 of 200+ 28M707 and here is it valve clearances for the L-head.

View attachment 67021

The valve clearances you are quoting are for an OHV engine not a L-head.

Now if can pick which of the following is your engine would help looking it up.
View attachment 67022

Click to expand...

I got the following specs

StarTech said:

Hmmm still not giving all the engine info but I took a look at 1 of 200+ 28M707 and here is it valve clearances for the L-head.

View attachment 67021

The valve clearances you are quoting are for an OHV engine not a L-head.

Now if can pick which of the following is your engine would help looking it up.
View attachment 67022

Click to expand...

heyinway said:

To remove seat...run a bit of mig or stick weld around the inner diameter. It will shrink and fall out. Of course you need a new replacement then

Click to expand...

thanks for the feedback, however I don't have a welder

any other suggestions?

I reviewed my findings and it seems that the valve specs are as I stated earlier:
Intake: .003 - .005 in
Exhaust: .005 - .007 in

My current clearances are:
Intake: .006 - .007
Exhaust: no clearance

Adevo said:

I reviewed my findings and it seems that the valve specs are as I stated earlier:
Intake: .003 - .005 in
Exhaust: .005 - .007 in

My current clearances are:
Intake: .006 - .007
Exhaust: no clearance

Click to expand...

Will you get off those specs as I am personally pulling the info from the dealer's Briggs' Power Portal.
Okay the specs for this 28M707-1162-E1 engine are the same as I previous quoted from Briggs Power Portal.

This is the last time I will repeat myself.

Valve Seat PNs.

And here is the instructions on valve seats from the service manual.

Personally I would leave the exhaust seat alone and just adjust the valve clearance if the seat is not pitted.

StarTech said:

Will you get off those specs as I am personally pulling the info from the dealer's Briggs' Power Portal.
Okay the specs for this 28M707-1162-E1 engine are the same as I previous quoted from Briggs Power Portal.
View attachment 67027
This is the last time I will repeat myself.

Valve Seat PNs.
View attachment 67024
And here is the instructions on valve seats from the service manual.
View attachment 67026
Personally I would leave the exhaust seat alone and just adjust the valve clearance if the seat is not pitted.

Click to expand...

Guess I'm full of apologies today ... got the damn specs off a "spec" sheet ... clearly wrong.

Thanks for your patience. Interesting that you'd leave it alone.

So even though the exhaust valve will travel further than the intake valve because the seat on the exhaust is pushed ... that's ok? Seems like the valves should be parallel to one another (only difference being clearances) to have the proper stroke forces. Am I wrong again? Wouldn't shock me.


Thanks again for your input.

Adevo said:

Thanks for you attempt to help me ... I love this guy ... his videos have helped me a lot.

Click to expand...

Why they don't cut the valve seats is beyond me.

The intake valve needs to be fully staked in the whole circumference, but the valve seats definitely need to be cut. The exhaust seat looks normal, don't mess with it, just needs cut.
Here is the valve seat cutter I use.

Fish said:

Why they don't cut the valve seats is beyond me.

The intake valve needs to be fully staked in the whole circumference, but the valve seats definitely need to be cut. The exhaust seat looks normal, don't mess with it, just needs cut.
Here is the valve seat cutter I use.

Click to expand...

Thanks so much for your help.

The exhaust seat looks normal, but it's definitely beyond the lip you mentioned - which explains why there's no clearance. It also has a tad of play when flush in the seat .. it can be pushed in further ever so slightly. In looking at the valve stem I see that's it's not completely square.

I love the seat cutter you use, but it's pricey.

If you think it's a good idea to trim the exhaust valve stem to get the needed clearance, I think that's what I'll do ... put the whole thing back together and see what I've got. If it doesn't start up ... I'll have to have to buy new seats and find someone to cut them for me (plus one valve that will be way too short to reuse).

Last time I'll bug you [pretty sure : ) ]

Thanks again!

I wouldn't invest much money in an engine that has had a loose seat. I would just grind the exhaust valve stem to the correct clearance and slap it back together and see how it runs.
This venture so far has given you a pretty good education in small engines.
If it had come into my shop, I would have advised against putting money into it.

"Last time I'll bug you [pretty sure : ) ]"




Bug us all you want, we enjoy trying to help folks fix stuff.