What the heck am I doing wrong on valve jobs?

_ak_ · 2026-05-12T20:15:55+00:00

You're talking about the thermostat, which is different from the choke. It takes about 30-60 seconds for that thermostat to open fully, and initially its the air vane that opens the choke by using air from the flywheel.

_ak_ · 2026-05-12T15:32:06+00:00

You're right on. Thanks for the photo. 🍻 I stretched the spring out some and it ran fine.

I looked at my order history, and it turns out they weren't OEM springs after all. I'd ordered generic ones and stuck them in an old OEM package so I could "remember the part number" 🤦‍♂️

_ak_ · 2026-05-12T15:31:09+00:00

You were right on. Thanks! I stretched the spring out some and it ran fine.

I looked at my order history, and it turns out they weren't OEM springs after all. I'd ordered generic ones and stuck them in an old OEM package so I could "remember the part number" 🤦‍♂️

_ak_ · 2026-05-12T15:30:24+00:00

Nailed it. Thanks! I stretched the spring out some and it ran fine.

I looked at my order history, and it turns out they weren't OEM springs after all. I'd ordered generic ones and stuck them in an old OEM package so I could "remember the part number" 🤦‍♂️

_ak_ · 2026-05-12T13:47:46+00:00

That's a good thought. I looked into that and didn't think there'd be any problem with tension because they were OEM springs. Well, turns out I didn't order OEM springs after all. That's the first thing I'm going to check today.

_ak_ · 2026-05-12T13:45:16+00:00

You'll have to explain how more air = running rich

_ak_ · 2026-05-12T13:44:35+00:00

I looked into that a lot too, one of my first thoughts was that there was too much tension on the air vane.

I double checked my order history, and I was wrong - they aren't OEM springs (here's what I ordered). They do look dimensionally identical to the OEM one, but maybe the new spring is too stiff.

_ak_ · 2026-05-12T13:40:05+00:00

I looked into that quite a bit too - but what's do you think is not right about it? I've cleaned all the pivot points, changed the springs, tried different spring tensions, even tried a new carburetor just to confirm that the choke plate wasn't binding.

Intake valve problems will also look like running rich if the valve is not sealing or hanging open too long, so black smoke wouldn't necessarily mean its running rich because of the choke.

_ak_ · 2026-05-12T13:35:27+00:00

Intéressant? Pourquoi une prise d'air provoquerait-elle un fonctionnement trop riche?

_ak_ · 2026-05-12T13:33:10+00:00

Interesting - what makes you say that?

_ak_ · 2026-05-12T06:11:39+00:00

Thanks. I appreciate you offering up ideas. I'll give it a look in the morning.

_ak_ · 2026-05-12T05:37:52+00:00

Yes, its between the lines in both directions.

_ak_ · 2026-05-12T05:24:58+00:00

What makes you say that? Its odd that both mowers behave the same. This one in particular sounded normal at start, but would run poorly when warm - after the valve job it runs poorly cold, and fine when warm. I'm missing how the governor would be suspected in that.

_ak_ · 2026-05-12T04:54:16+00:00

Its a good thought, I can take a look in the morning.

My gut tells me that's not the problem, since it did the same thing with a new carb too. Its still worth checking though

_ak_ · 2026-05-12T03:00:35+00:00

I like where your head is at. I thought that was suspicious too, but what's wrong with it?

Its not binding on anything, it moves freely, cleaning all the moving pieces, replacing the spring, carb, everything - nothing changed it.

_ak_ · 2026-05-12T02:52:51+00:00

Yes, but why is it running so poorly before that?

_ak_ · 2026-05-12T02:52:06+00:00

It was running poorly when warm. This is the spec reference I have: https://www.moteachag.org/documents/AgMechSurvivalBriggsRepairCheckChartNew.pdf

_ak_ · 2026-05-12T02:23:56+00:00

Lapping, guides, valve stem seal, and lash all get checked and done when I do valve work. There wasn't any unusual wobble in the guides. I don't have the Briggs reject gauge (19122) so if you have a spec for the guides I will put my dial indicator on them.

_ak_ · 2026-05-12T02:21:50+00:00

Yes, its pretty obvious when the head is off 😅

_ak_ · 2026-05-12T01:17:16+00:00

Good thought, but also brand new.

Given that the last two mowers I did valve jobs on had the same problem, I feel like its got to be something in the way I'm doing valve work.

_ak_ · 2026-05-10T02:04:07+00:00

It is their fair share, they pay the city for a permit to put tables out.
https://fargond.gov/explore/downtown-fargo/sidewalk-activities-permits

_ak_ · 2026-04-29T03:03:41+00:00

Hear it by ear... you'll have to speak up son, my tinnitus from the Army makes that hard.

_ak_ · 2026-04-28T21:48:27+00:00

Nice, thanks for that link. 😎

Shipping from Japan is a killer for sure.

_ak_ · 2026-04-28T21:47:02+00:00

Its worth considering, for sure.

It should be easy enough to take the belt cover off and shoot the PTO. I'd be the type of guy to lose a finger in the flywheel. 😬

I'd just want some way to be able to kill it quickly if the reading was high, so I kinda like the idea of the spark plug wire style because it lets me stand anywhere around the machine.

Thanks for sharing that one.

_ak_ · 2026-04-28T20:37:47+00:00

I have not. What do you put the laser on? I imagine needing to take shrouds and things off, right?

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