Honda Izy running weird

[Dave_garden]

hi, i have a 3yr old honda izy 16" which has always been reliable. this summer having retrieved from the shed its not been running its best and can't determine the issue. have done a full service of air filter, oil change and new spark plug, as well as cleaned out carb and exhaust ports. easier to watch (listen) to whats going on in the video link, but it seems to be struggling to maintain a constant idle/running speed.

 

[Burnerman]

From the video sound, it could be the choke stuck on a bit Dave.....is the machine chuffing black smoke at all?
John

 

[Dave_garden]

No smoke at all. White or black. That’s been fine. It’s an auto choke model and not sure how to adjust or check.. any other thoughts?

 

[Burnerman]

After the engine has run for a while, take the outer cover off from the air filter and see if the choke butterfly is open, will you? It takes a minute or two for the engine to get hot enough. This will rule out the choke operation from the equation. Often the auto choke Izy will chuff a bit before clearing itself if the choke comes on a bit too readily.
John

 

[mrrusty]

Identical mower to me. Mine did this, and I tweaked the governor by loosening the clamp on the governor arm and resetting it. Can't remember exactly how I did it, but the method/answer was on t'internet somewhere. It sorted the hunting 100%

 

[blup]

Mine did this after 8 good years, was fine after letting it run for 5 minutes without a load, seemed to clear itself.

Blup

 

[Dave_garden]

ok thanks for the responses. finally dry enough to actually test some things! ran it without load for ~5 mins - which is when it just conked out. auto choke is open when cold and watched as it slowly closed as engine ran. hunting just got worse until dying.. doesnt sound the same as above. have also adjusted the governor to open throttle point slightly. has helped but still hunts even with higher revs. back to the drawing board currently

 

[Burnerman]

The choke flap should be closed when the engine is cold and within 2 minutes should be fully open.
Inserted into the casting near the carburettor is the auto choke capsule (google an image maybe) and it has a rod that expands out of it with heat, opening the choke flap.
You have to remove the carb to get at it and it mustn’t be reinserted in the warm position.
Can you investigate further?
John

 

[Dave_garden]

ok that might be my open/closed mix up. watching the choke move as it warms up it appears to be working as normal moving from one side to the other after ~2mins. once it gets to the fully moved position this is when it dies. its almost like its working in reverse!

 

[Dave_garden]

perhaps an air blockage somewhere else then?

 

[Burnerman]

Just a wee bit of logic here Dave.....if the choke flap is fully open there isn't much vacuum in the carb venturi so any jet blockage causes the engine to falter. Closing the choke flap increases the vacuum and draws more fuel through.
So, if it was mine it would be carb off (after cleaning the outside with aerosol carb cleaner) then float chamber off and float out, followed by the main jet and emulsion tube directly above it. Absolute cleanliness is essential, and compressed air helps but you should get by with the carb cleaner. No rags or wipes permitted here!
John

 

[Dave_garden]

so by jove you nailed it! cleaned carb with carb cleaner spray in and out, back together and now running well.. too well in fact! going to have to reign in the revs/throttle adjustments - think its going to take off

 

[Burnerman]

Delighted to hear it, and well done!
The Izy engine will last a seriously long time with regular oil changes, but the deck won't......if you can be bothered, drain off the fuel and oil, tip the thing right over and scrape and paint the deck underside.
Cheap blades and service parts available from GHS Ltd when the time comes.
John