Zenoah G45

Have you cleaned all the internal passages in the carb ?

There are, depending on the specific carb, one or two passages which are very difficult to flush - sometimes you have to remove the "Welsh" plugs to get those passages cleared.

Fuel/oil mix, if not cleaned from the carb, can form sludge/varnish in the tiny passages, and the carb will never work properly until those passages are cleared.

Most lawn mower repair shops have the Welsh plugs in stock

Here's a check-list gleaned from gswarbirds@yahoogroups :

Engine Trouble Shooting Check List (fuel related w/walbro type carb):

1) Using fresh gas and oil mixture---check/replace

2) Air getting into fuel line through pin hole or crack---check/replace

3) Clogged or dirty fuel filter if using one and/or blocked or crimped fuel line---check/replace

4) Carb diaphragm hardened or dirty limiting it ability to fluctuate---check/replace

5) High and low mixture needles out of adjustment or worn in their seats---check/adjust/replace

6) Dirt or gummed up fuel in needle seat underneath carb cover---check/clean

7) Nick or burr formed by wear or other defect on needle fulcrum pin that inhibits the free rocking action of the fulcrum---check/deburr

8) Needle Fulcrum bent/damaged---check/adjust/replace

9) Dirty screen in carb---check/clean

10) Blocked or partially blocked fuel jets and internal passageways---check/clean

11) Dirt and gum under welch plugs if applicable to your carb---remove/clean/replace

12) Air leak between carb and cylinder head---check/replace intake manifold and/or gasket(s)

13) Air leak between crankcase halves---check/tighten/replace gasket

14) Air leak between cylinder head and crankcase---check/tighten/replace gasket

15) Crankcase pressure reduced due to auxiliary pressure tap e.g. smoke/chain oiler etc. --check/adjust

16) Air getting into crankcase through faulty bearing and/or seat---check/repair

17) Cracked cylinder head or crankcase---check/replace

18) Blocked exhaust due to the work of insects like mud-dobbers/dirtdobbers---check/clean

19) Loose spark plug---check/tighten

20) And finally if all the above fails to get your engine running and you don't have ignition problems---USE THE ENGINE AS A BOAT ANCHOR---LIFE IS TOO SHORT!! Just kidding of course:)

Cheers, Fred McClellan The House Of Balsa Dust

Have you taken the butterfly out? If so, there's a small hole in the carb throat whch must be covered/uncovered at lower speeds (I don't remember which). This may very well be your problem. If the butterfly is put in backwards, the engine will run roughly and may not run at all below 1/2 throttle. Dr.1 Driver "There's a Hun in the sun!"

I made this mistake on a Quadra 42...

Talk about feeling stupid once I figured out what was going on..

Chris

Dr1Driver wrote:

Betcha the tiny holes in the venturi throat are blocked....at least one of them (there are three). I clean them out with a fine soft copper wire bent at 90 degrees. Good luck. Mitch>

It's running again!

Thanks for the help - I stripped the carb, left it in engine cleaner for a day, then used used the copper wire trick, and let rip with the compressor gun. No dirt could ever survive an onslaught like that.

Everything's back to form again.

Cheers

isnt it amazing what the smallest piece of foriegn material can do to ones day !?!?! GOOD to hear its running.