QuestionQUESTION: i have a briggs 18hp opposed twin, i'm having issues with the carb on it, it seems to be allowing to much fuel to enter the manifold, not to the point of flooding, but it causes it to run at near full throttle, and at low throttle, it will idle properly for about 30 seconds, then rev all the way up, hold that for about 15 seconds, then idle down. i rebuilt the carb, and everything was done by the book, had exploded diagrams, everything was thouroughly cleaned, but only two months later, and after about 50 hours, its acting up, since the rebuild it has always surged slightly, but never this bad, i worry about permenant engine damage from this reving. is there anything i've possibly overlooked. the engine is a 422707 - 0179 01 - 86092512. thanks.
ANSWER: Most surging problems are caused by the carburetor. I would start by removing and cleaning the carb with compressed air from an air compressor. Blow compressed are through all the internal carb orfices. Re-install carb and see how the engine runs.
Since the engine is a 1986 model, the carb manifold gaskets could be leaking but usually you get a lean running engine with an intake leak.
When was the last valve service?
The last part to replace is the governor spring as they rarely fail but they can loose tension over time.
Clean the carb and let me know how the engine runs.
Eric
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QUESTION: I removed and cleaned the carb, new gasket kit, still the same problem, i ran the engine with air filter assembly off, to note throttle plate position, and despite the plate being closed to idle position, it still revs way up, the valves appear to be seating properly, engine has good compression, well over 100psi, i have good spark on both cylinders, and for the most part the plugs are decent, its just like the engines getting to much fuel/air. I'm quite frustrated with this, mainly because it won't idle down. governor springs seem a little loose, but i don't think this is the problem, because the governor closes the throttle when it revs way up.
ANSWER: You didn't adjust the governor or anything did you? Did you ever remove the governor arm?
Have you checked out this link:
http://engines.myfaqcenter.com/Answer.aspx?p_faqid=3435&body_0$tbKeyword=governo
Eric
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QUESTION: nope, haven't done any work with the governor, still factory settings, I'm gonna be removing the whole intake manifold and carburater assembly tonight and tear the whole carb down again and let it soak over night in some parts cleaner, and gonna reassemble with new gaskets for the intake manifold, and see if this helps, when i last diassembled the carburater, i had adjusted the float needle, and it helped to some extent, so i'm thinking maybe the float pivot is binding and allowing the fuel pump to push to much fuel into the manifold. if all else fails i'm probably gonna have to get a new carb, i don't want to mainly because they run like a buck fifty. i thank you for your assistance thus far...
AnswerI have had carburetor inlet needle bores wear and cause the needle to bind causing rich running engine.
Is the carburetor shaft wore? Seen shaft wear but usually leads to a lean condition as air travels around the shaft rather than the carburetor venturi.
Is the engine over speeding?
Eric
