Join Date: Jun 2006
Posts: 101
AL
03-08-11, 02:17 PM
#1
thermostat B&S 12S902
I have a b&s 12S902 engine on a b&s pressure washer. It was running fine them started to sputter and quit. I have cleaned the carb and replaced needle valve and seat. It ran good again and then the same thing. I see it has a thermostat connected to the choke valve and wondered if it could be the problem. Is there a way to check the thermostat? thanks
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Join Date: Mar 2003
Posts: 16,683
NC
03-08-11, 03:21 PM
#2
When is the engine dying? Is it soon after starting or after it has run a while and gotten up to full temp or is it just dying randomly?
I have never seen a thermostat on a small engine.
I have never seen a thermostat on a small engine.
Join Date: Jul 2006
Posts: 754
NH
03-08-11, 04:50 PM
#3
I had never seen a thermostat on an air cooled small engine either, but here it is. #291. And since it is connected to the choke link,I would look into it further.
Parts and Diagrams for Briggs and Stratton 12S902-1368-B1
Parts and Diagrams for Briggs and Stratton 12S902-1368-B1
Join Date: Jun 2007
Posts: 1,761
KS
03-08-11, 05:14 PM
#4
That looks like the same thing on the Kohler XT engines Chinese made, they call an "Auto choke". Not seen one not work, usually it is the carb, needle and or seat leaking and the kit is a new carb.
Haven't seen one with a briggs tag tho.....
Haven't seen one with a briggs tag tho.....
Just needs a bigger hammer

Peace
Join Date: Jun 2006
Posts: 101
AL
03-09-11, 06:09 AM
#6
Thanks for replies. I tried holding choke open, no luck. put gas in plug still no luck. checked spark and it is good. decided to check compression. I have a screw in type compression testor. It showed 30psi. that does not sound good but I don't know what it should be. do you know what the compression should be. it is a 8.75 hp 12S902 engine. thanks
Join Date: Mar 2003
Posts: 16,683
NC
03-09-11, 07:14 AM
#7
I usually do a leak down type compression check so the compression release does not come into play.
Make sure you have the carb. removed or wire the butterfies wide open. You are right, 30 psi sounds quite low. I assume you tested with the cylinder dry. Did you try testing compression after squirting some oil in the spark plug hole?
Make sure you have the carb. removed or wire the butterfies wide open. You are right, 30 psi sounds quite low. I assume you tested with the cylinder dry. Did you try testing compression after squirting some oil in the spark plug hole?