Im new to the sight and some what new to mowers, so bear with my rambling sentences. Im fixing my buddys tractor (MTD 20hp-Twin) for him and i ran into an issue. It has an idle surge at all times and can be corrected for a few seconds by holding the choke about 3/4 of the way out but then starts to flood. we took the transaxle out of it and had the intention of welding it up but never got around to it. That was a year ago and we decided to put it back together. but it sat for a whole year with bad gas in it so as soon as i got it back i cleaned the carb spotless. it fired first start but within 10 seconds started to surge. it would drive though and pull its self around fine. But after a few several hour romps it still surged and goes back and forth being able to move with out stalling, sometimes it will sometimes it wont. the best i can figure there is something wrong with the governor, because it just bounces up and down. I have a link to a crappy video showing the surging, best i could do before my nosy neighbors came over and started bothering me haha
the problem now sounds like bad gas. drain the tank and bowl on the carb. The carb will probably need cleaned after sitting for a year . make sure you clean out the low speed circuit good, that was the problem before you parked it for a year.
Stretch44875 Administrator
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Age : 49 Join date : 2012-04-05 Points : 5692 Posts : 959 Location : Mansfield, Ohio
I have the same engine. Cleaned everything and it ran too lean. Did some research and these engines are set too lean for emissions, and there is no adjustment. Found some information on hey mow about removing the main jet and replacing it with a adjustable needle jet. Removed main jet, and removed fuel shut off soloniod on bottom of carb. Then I used an old tecumseh needle that I rethreaded to fit where the fuel shut off was, now I can adjust the fuel, and it runs perfect.
Mine did the same thing. I got to noticing the engine RPM would slow until the governor spring would engage (the spring was very loose), then the RPM's would rise. I cut a couple of coils off of the spring, (in effect shortening it) and that fixed the problem. Let us know what you find. Tom
dangeroustoys56 Veteran Member
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Age : 54 Join date : 2010-02-10 Points : 7067 Posts : 1726 Location : Florida, USA
Keep mind when the gaskets inside twin cylender carbs get older, they swell and leak - causing running issues - i have a 99 hydro murray that wouldnt run for crap, no matter how many times i cleaned the carb - put a new carb kit, pump internals , cleaned it really good and it runs great now.
Subject: 
June 11th 2012, 9:46 pm
