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Honda G400 problem

Started by Apiti Jack, October 10, 2016, 08:11:37 PM

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Apiti Jack

I've a stand-alone (not driving anything at this stage) Honda G400 that's driving me bananas. 
To get it started full choke is needed to (just) keep it running, roughly. When the throttle is altered there is no change in motor revs. I've checked timing (the gear marks are correctly aligned), have lapped both valves (has excellent compression), set gaps correctly, and cleaned the carby thoroughly. Even so there has been no performance change; it's bad. It appeared to be running lean, slightly retarded and running hot.  There was some backfiring too and then stalling. After reaming out the main jet a tad it ran smoothly, with throttle operating properly and idling normally.  But next day with the air cleaner on now, it returned to those earlier symptoms, with hit and miss firing, and backfiring (one massive backfire sheered the flywheel key), but this time without needing choke to keep running briefly and roughly. It has a CDI unit (how to test that?). Suggestions welcomed. Unfortunately, it's on the way to becoming an anchor.

sawguy21

Did you clean the nozzle above the main jet? Sometimes they need a little help to remove. I started dealing with Honda in the early 80's and the G400 was already discontinued.
old age and treachery will always overcome youth and enthusiasm

Apiti Jack

Thanks for the suggestion.  Did you mean the "emulsion tube" which can be pushed down from inside the carby throat and then drops out the bottom after the main jet has been removed? Yes, go it out and cleaned it up too. I'm sure you'll know the little tricks for getting the unit to tick over.  More hints welcomed.  Cheers, JohnK

timberlinetree

I had a saw with a bad coil that would act up on different days in different ways. I thought it was the carb at first. Good luck!
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Riwaka

It was a long time ago. I remember using lawnmowers with one of those engines. One mower was hard to start, the discussion was it was the overall design of motor was the problem so the whole mower was replaced with one with a Honda GXV engine that was very reliable.
The other mower had a hydrostat drive that packed up before the engine did.
http://www.ereplacementparts.com/honda-g400-type-qb6vin-g40010000011096247-small-engine-parts-c-37657_37658_37986_37701.html

Most repair shops tend to replace the entire Honda engine now if the problem is not obvious rather than fiddle with parts.

Apiti Jack

Mia culpa -- the G400 is now purring. It was a simple fix and yet invisible too.  When a tooth broke on the ring gear of my CDI model I found a points-ignition G400 and used its flywheel since these are the same size with identical ring gear.  BUT, there are just two magnets with the points-model and four with the CDI one.  In effect then my CDI G400 motor was two-cycling.  No wonder it was running rough.
Many thanks to those who replied.

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