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Discussion Starter · #1 ·
Hello out there! I have a Honda "GCV" engine from 2008 on a Mcculloch mower. The engine only runs smoothly on half-choke. With the choke off the engine revs up and down constantly. Any thoughts? I was leaning towards an air leak in the carb. The plug, air filter and fuel are all new.:dunno:
 

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Does sound like a dirty/leaky carb to me. I bet a rebuild with some new gaskets might be the solution to the problem. Just make sure to check for play in the throttle and choke shafts. Excessive play will create an air leak. Some are replaceable, some are not. Sometimes a new carb is cheaper than rebuilding one with worn out parts.
 

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On the Honda carbs, I dont think I have ever had to do a full rebuild, just a float needle at most. Pull the center jet (make sure to use a good screwdriver and lots of downward pressure or you will strip the jet out!) pop out the tube and clean all holes. Remove the idle stop screw and pull put the plug under it, shoot air through everything and reassemble. Out of 50 of these I bet I have only had to replace 1 bowl gasket, unlike Briggs or Tecumseh where you better replace everything.
 

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There is a pdf. of instructions on cleaning Honda carbs in the "Honda" section of our forums given to us by [email protected]

You can find a short video here on the proper method to clean the GCV carb as well.

Look under "Service" then "Service Movies". It's video only, no sound.

There is other valuable information to be found under "Service Information".

Honda Engines Europe EEC
 

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Discussion Starter · #5 ·
Ok, here is where I am at now. I cleaned and rebuilt the carb, changed all the gaskets. The engine starts right up and mostly runs fine. It still will rev up and down a bit from time to time. Any ideas what else this could be? Thanks!
 

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I would check to confirm that the throttle and or governor linkage is not loose or adjusted incorrectly. When it's revving up and down, or hunting, I would look to see if you can (safely of course- consider removing the blade for investigation purposes while it's running) if the linkage itself is moving back and forth with the speed of the motor. This may help give you an idea if the problem lies in the linkage or is due to something else like spark.
 

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Discussion Starter · #7 ·
Thanks Austen! Would you happen to know how to adjust the governer on this type of engine?
 

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There is a fine wired spring that attaches to the governor arm and carb called an anti-surge spring. Make sure it's attached. Here's a service manual for the GCV160. Take a look at page 79. The governor adjustment is explained there.
 
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