Tecumseh 4 hp carb

Airmaster Flyer

Forum Newbie
Joined
Dec 29, 2022
Threads
1
Messages
6
My Snapper 422 snow thrower with a Tecumseh HS 40 engine was working but acting as if it was too rich and using fuel much faster than it should. First thing I found was that the fuel supply hose had a slit in it. Replaced hose, but engine was still not working properly. It would start, and then begin acting as if it was too rich, and shut down. So I decided to check out the carb. Removed it, cleaned it and checked all settings. Float floated, and when I blew through the "fuel in" port, and pushed up on the float, it sealed. Put it back on the engine. It started immediately, but then bogged down and quit. With the engine off, fuel would drip out of the choke end of the carb. Obviously the needle and seat were not shutting off the fuel. After messing around with it off and on for about two weeks, I purchased a new carb. Works great. Snow thrower starts immediately, and seems to run well, except that at full throttle, it begins to miss a little. If I reduce the throttle slightly, it smooths out. Maybe too rich at full throttle? But the new carb does not seem to have an adjustment for the mixture. No adjustment for the idle mixture either:

New carb.jpg

Is there a way to adjust this type of carb? Perhaps I can remove the adjustment screw from my old carb and install it on the new one?

Thanks for any help, Bob
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,865
I would say the new carb is slightly too lean in the complete full throttle position. Could try using the bowl nut off of the old carb and see what happens. The main fuel jet is in the bowl nut. And would bet the rubber float seal tucked up inside the fuel inlet has either swelled or cracked/damaged which is what is causing the rich run issue and the flooding.
 

Airmaster Flyer

Forum Newbie
Joined
Dec 29, 2022
Threads
1
Messages
6
Thanks for the reply. I thought to replace the needle and seat of the original carb, but seat did not seem to be replaceable. When I purchased the new carb the description stated that it was for a 5.5 hp, 22 inch snow thrower. My 422 model is 4 hp, which is what leads me to believe that if anything it would be too rich rather than too lean. But now that I think about it, you are correct that if I can back the throttle off and it runs better, that would be a symptom of too lean at full throttle. Maybe in the Spring I will take the carb apart and see if an adjustable main jet can be substituted, and if that makes any difference. Right now I want to leave things alone so my wife has a working snow thrower!
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,865
The float seat looks like an O ring of sorts as illustrated in this picture


The rubber seat will swell or crumble when exposed to carb cleaner. Also on Tecumseh the float when properly adjusted for height doesn't sit level. you should be able to slide an 11/64 drill bit between the float and the carb body without the bowl gasket installed opposite from the hinge pin. And also be aware that a carb set at warm temperatures will run lean when operated at cold temperatures. Back when we had adjustable Tecumseh carbs the procedure when setting them in the fall during tune up was to set the main jet to run smooth and then turn it out 1/4 turn to compensate for the denser air in winter. Otherwise it would run poorly when the customer started it to blow snow.
 

Airmaster Flyer

Forum Newbie
Joined
Dec 29, 2022
Threads
1
Messages
6
As I already said, I installed a new carb. I don't need any information on the seat or how to adjust the float level. The question I have is: Is the main jet mixture adjustable, and if so, how?
 

Airmaster Flyer

Forum Newbie
Joined
Dec 29, 2022
Threads
1
Messages
6
Thanks for the comments. The one that I ordered used that same stock photo of one with the adjustable main jet, but the one I received did not have it. It says it is compatible with the HS 40 Tecumseh.....I may try that in the off season. Right now the machine runs OK, and I don't want to mess with it. Warm this week, but with my luck if I take the snow thrower apart again, we will have 2 feet of snow!

Bob
 

mmoffitt

Well-Known Member
Joined
Aug 21, 2018
Threads
1
Messages
115
We are off to a good new year!...
Happy new year everyone
 

shadetree#1

Well-Known Member
Joined
Oct 31, 2022
Threads
1
Messages
153
Here is a link to view some Tecumseh carbs with repair tips.

You can also download a FREE Tecumseh L-head service manual that cover several model and Hp of the L-heads.
You might try these links for the free manual:
I have not visited these links lately.
I think the smallengine link is a direct download.



https://www.smallenginesuppliers.com/html/engine-specs/tecumseh/Tecumseh_L-Head_Engines_Service_Information.pdf

Take care of your old adjustable jet carb, they are NLA and are good carbs.
Pay attention to the little o-ring on the bottom of the bowl where the High speed jet screw is located. If it's bad or gone and the little flat washers that is used to keep from worrying and damaging the o ring is gone the carb will have a aggravating leak.

Sometimes you can clean up the seat using a q tip and tooth paste.
 
Last edited:
Top