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Small Engines (Lawn Mowers, etc.)/carburetor problem - possible flooding
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Question
I have a craftsman lawnmower with a 6 horse briggs & stratton engine. The lawnmower was manufactured in 2003. When mowing, not right away after the engine is warmed up, it seems to lose power, start running rough then dies. After it dies I can't restart it. Acts like it is flooded. Also I've noticed when it sets overnight gas leaks out of the carburetor not by the bowl but up by the air filter, like the float is not shutting the gas off. We've replaced the valve needle and seat, the float and pin. Still when left overnight gas still leaks out of the carburetor by the air filter. Since there is no adjusting these carbs they seem simple but this one is giving us fits. Any suggestions on how to stop the leaking. I also assume this is causing the flooding while it is running. Something isn't shutting the gas off. Thank you.
Mike
Mike,
There is no advantage to installing two seats in the carb as it would end up leaking past them and you would be unable to set a proper float level because you wouldn't be able to bend the float height tang enough to make up the distance taken by the extra seat. One properly installed seat will suffice. Make sure you bottom the new seat correctly in it's position with a pin that is just slightly smaller in diameter than the seat (non-cutting end of a drill bit will work) and make sure there is no debris under the seat before installing it. Set the float height so the float sits parallel to the float bowl mounting lip (check by turning carb upside down). If you have a plastic float rather than a brass one (which you can bend the tang to adjust), you will have to assume the float height is correct with the seat properly installed. Hope this helps.
There must still be an issue with the needle and seat and/or float and/or pivot. These are the only things responsible for controlling the fuel level in the carb. That is likely causing the running problem as well (you should notice some black smoke from exhaust too). Let me know what you find. Hope this helps.
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| Rating(1-10) | Knowledgeability = 10 | Clarity of Response = 10 | Politeness = 10 |
| Comment | Marc. . .thanx!. . great analysis. . answers to your questions. . 'choking out' was a bad description as it's not getting gas to the plug. when stalling, it seems that the governor is kicking in and opening the throttle-plate completely. there IS gas in the bowl when i take off the top 1/2 of the carb (maybe 1/2" or so) and no. . .i didn't use wire in the jets/tubes etc. only compressed air and carb-cleaner; however, if it was accessible or removable, i verified pass-through by both light visibility and blowing through it. it's not a cut-off switch as i've verified continuity and functionality of each. . . and i CAN catch it, dis-engage the deck or shift to neutral and keep it running by playing with the throttle. checked and cleaned the cylinder vent casing also. . .i'm stumped. this carb has a fixed high-speed jet which i can't adjust or verify it's condition - while not a mechanic, i'm usually pretty handy at this . . .i also tested the mag-output and it's constant and in range. my little brain keeps telling me it has to be carburetor or governor. . .but, i believe the governor either works or it doesn't and there's not much to that. . the external governor linkage and brackets all appear to function normally. . .throttle plate is marginally opened when running at virtually any speed, until it opens wide and stalls-out. don't mean to be a pest, but sure do appreciate your guidance. can be reached e-mail direct at rpilotg@aol.com should you have any other ideas. thanks, again. | ||
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Small Engines (Lawn Mowers, etc.)
Answers by Expert:
Marc Mielhausen
Expertise
I work on equipment in my spare time for myself, family and friends. I have experience in troubleshooting and fixing lawnmowers, string trimmers, chain saws, tillers, snowmobiles, inboard and outboard motors. As I am not currently employed in this industry, I can be of assistance more in non-brand-specific diagnostic questions. Try me.
Experience
15 years experience (6 professionally & 9 personally) Also have related experience in automotive manufacturing, machining, precision measurement, gauge and fixture design. As long as I can remember I have been troubleshooting and repairing mechanical devices of all types.
Education/Credentials
Ontario Certificate of Qualification for Marine and Small Powered Equipment Technician (1993)
Mechanical Engineering Technician - Materials & Quality (1997)
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