Older Mitsubishi generator

[trooper1954]

Hi all,
Have a Mitsubishi MGE5800 generator that I've resurrected...hadn't run for about ten years. It's running, puts out 120v and maintains this when under load. I put in a new "chinese" carb as I couldn't find an original replacement, and even with a new carb it's surging while running......anyone any ideas as to why? I've tried spraying all lines with carb cleaner while its running to check or air leaks,but that doesn't change anything.
Thanks for any help.

 

[PoorUB]

Open up the idle mixture screw (If it has one) a bit and see what happens.

What the deal is under light or no load the throttle plate closes enough to draw fuel from the idle circuit in the carb, but there isn't enough to supply the engine for what it needs so the RPM drops, then the governor tries to pick up the RPM and goes wide open for a split second and pulls the fuel it needs from the main jet and recovers, then the process starts all over.

If you can get the engine to idle, you may have to force the throttle closed, then adjust the idle mixture so it idles smoothly.

 

[rustyzman]

It would be worth opening up and cleaning the new carb. I have had many of the chinese carbs that had bits of materials leftover inside causing restrictions again and again. Generally clogged ports or jets need to be cleaned by disassembly.

Also consider putting a full size fuel filter inline too, as a deteriorating fuel hose or dirty tank will give you the same issues.

 

[yatg]

What @rustyzman said. Put a brand new chi carb on an engine I was working on. ran like poop. Took the original carb, cleaned it real good, transferred parts from the new to the old body and it fired right up.

Also what @rustyzman said. Clean your tank real good, new fuel lines, inline filter, and a shutoff before the filter makes future maintenance easier. Check if there's an in-tank filter and replace it too.