Surging on an LA175

[jpilk99]

Hi all. I work on a lot of small engine equipment, and am often stumped by "surging". Often times, carburetors need a good cleaning, or swapping, and that resolves the issue. But on my LA 175, with 250 hours, I recently removed carb and cleaned it ...pretty thoroughly. (Not saying I'm the best bench mechanic in the world, but, I really go through - carb cleaner, wires and carb brushes to clean plumbing, etc.). I even bought a new fuel pump but nothing resolves the surging; see and listen to 7 second video here: John Deere LA175 surging

I will say that happen only on initial cold start and smooths out after 20-30 seconds. It also happens when I'm mowing and come to some heavy/thick/tall grass and smooths out when I'm a few seconds past it, or if I really slow down and slowly go through it.

Lastly, and to no ones surprise I'm sure: If I hold the ...throttle arm connected to the governor, and hold it in place while it was surging - it runs smooth. (I guess that's probably an obvious statement).

Someone suggested fuel line. I keep coming back to a new carb... Thanks for any help/suggestions.

 

[beenthere]

If I hold the ...throttle arm connected to the governor, and hold it in place while it was surging - it runs smooth.

Thought fuel supply (fuel pump ? ) might explain the surging when tough mowing, but the governor in the LA175 may be related to air being moved around the flywheel and needs cleaning.

 

[jpilk99]

Air being moved around flywheel? Never heard of that. And you suggest cleaning the flywheel??

 

[jpilk99]

Ah, good ol' Taryl. Very helpful videos - painful sideshow BS (IMHO). Maybe my buddy was onto something with replacing the fuel line, as the surging was going on pre-carb removal & clean and post. And I cleaned the mating surfaces and new gaskets before reinstall so don't think I've got leak there, but, will check. I ain't perfect. Thanks again Sarge

 

[tomplum]

A couple of things regarding surging on these. It could be internal in the carb if you hadn't replaced a couple of the key seals. The moth gasket, lower o-ring and seals on the mains all need to be good. The flat domino one too, but there are less issues. You can buy them separately rather than buying the whole high $ kit. But externally these plastic intake manifolds can leak both at where it mates to the carb and at the seams. New seals at the heads are always a good idea. Always try the donor can trick and draw fuel direct from the can rather than back through the entire fuel system. If you have success with this, then you know quick that you have a supply problem. Checking the static governor adjustment is simple and a good thing when you are dealing w/ surging.

 

[jpilk99]

Great stuff, Mssr. Plum! Thank you.

 

[duffer]

Watched a YT video and the guy's problem with his surging was a plugged up gas cap vent. Might want to clean yours if you haven't lately. Not saying that is your problem, but it might be.

 

[jpilk99]

Thanks Duffer

 

[tkcomer]

The surging at full throttle on my LA145 was caused by a small crack in the vacuum line.

 

[Richard001]

The surging at full throttle on my LA145 was caused by a small crack in the vacuum line.

Can you please expand on your post. I am not aware of a vacuum line on a small tractor.