Carburetor - I'm not giving up on that lawn tractor after all (pics inside)
 

Continued from https://www.gassavers.org/showthread.php?t=10792

Engine: Briggs & Stratton OHV 15HP vertical shaft 28n707-0162-01

A bunch of corrosion in the carburetor... :(

The float needle is corroded, and the seat is corroded badly. How is the seat removed? Can I wirebrush/sand the corrosion or do I need to replace this stuff?

Zoom in for close resolution on these pics at the album:
https://picasaweb.google.com/bovinity...e/EngineRepair
I can post more pics including zoomed out pics if that would help.

Fouled (and now broken) spark plug:
https://lh5.ggpht.com/_SX8ccPdZj5c/Sh...0/IMG_2815.jpg
It's not as oily as it looks. It's more dry than it looks.

Needle:
https://lh6.ggpht.com/_SX8ccPdZj5c/Sh...0/IMG_2849.jpg
https://lh3.ggpht.com/_SX8ccPdZj5c/Sh...0/IMG_2863.jpg

Underside of carburetor with bowl/float removed (see all the corrosion on the needle seat and such):
https://lh6.ggpht.com/_SX8ccPdZj5c/Sh...0/IMG_2864.jpg

Corrosion visible on the, uhh, main jet I guess...and what's with what looks like smoke marks around the throttle pivot? I don't think it was backfiring through the intake or I'd see it on the intake pipe which is clean as a whistle.
https://lh3.ggpht.com/_SX8ccPdZj5c/Sh...0/IMG_2847.jpg
Edit: Note - that picture is upside-down.

Here's how it looked shortly after the fire when I took off the upper housing thingy:
https://lh4.ggpht.com/_SX8ccPdZj5c/Sh...0/IMG_2812.jpg

I've removed the lower housing sheet metal visible in the last pic. I intend not to replace it. Is that ok?

Where do I go from here? Try to clean up the corrosion? Replace needle and seat? Replace the whole carburetor?

As you can see it's a good idea to pull the shroud at the beginning of the season and check for mouse nests. Nest=overheat=fire. Put all the tin back on- they didn't put it there for their health!

Just clean it all up and slap it together. Use carb cleaner or solvent. Don't let it sit with old gas over the winter next time. Looks like it got awful damp.

I'd leave that sheet metal on- it likely directs the cooling airflow around the cylinder. You may end up with a warping effect if one side of the cylinder is always hotter (expanding more).

It looks like you weren't getting much air cooling at all with that mouse nest!

I think a rubber tipped needle will work fine in that seat. Just wrap a nail tip with extra five sandpaper and give it a few turns in the seat.

yea might need a stiff small brush to clean that after you spray it with carb cleaner.

the needle looks like it needs replaced. but could try cleaning first.

i must say i have never seen green corosion in a carb...and we let gas sit all winter in our mowers....start right up in the spring too....

could be extreme moisture.

obviously the mouse nest is what caught fire, make sure you clean all the cooling fins free of debris.

I was thinking that the sheet metal thing was just trapping gunk and preventing airflow, but I can imagine it directing airflow from the fan. I'll look more closely. I was assuming it was just a guard or aesthetic.

The fire was at the bottom, the flames didn't reach the top of the valve cover.

I do not let gas sit in it all winter.

So, I should buy a new needle and try to smooth the seat?

What did the book say the corrosion was caused by?

Unless you have a rubber tipped needle, you'd need a very fine finish on the needle / seat to make a seal, right? That rules out scratching it up too much during cleaning. Personally I'm cheaper than I am lazy: try cleaning it and see if it leaks.

I don't think the book says anything about corrosion. I'll have to do some reading.

I am confused. I thought they had pictures showing the very same thing?
That needle is rubber, right? Either that or it's got weird colored corrosion on it!

They have pictures showing what looks like the same model with the same setup...but not in the same condition.

I can't tell if it's rubber or not. I'd assume that one of those colors is rubber.