Hello,
I have recently embarked on rebuilding a MTD / ACE lawn tractor that has been abused, it was left to sit in the woods with bad gas in it for about a year. The tractor has a Briggs 287707 14.5hp ohv engine in it and a nikki carb. After a thorough cleaning and dumping the gas in the carb and tank as well as lightly cleaning the carb, the engine started. It however will not run with ought the choke 5/6 the way out on full throttle, and all the way out on low throttle. I have read through countless other posts on this forum as well as others directing to thoroughly clean the carb soaking overnight etc. I have done this twice now, I soaked all parts in carb cleaner and scrubbed all deposits off it looks like new. In fact it almost is new this mower is only four years old! The gaskets in the carb are like new and I cleaned all passages using a piece of copper wire. I don't think I have ever seen such a clean and good looking carb I'm actually pretty proud except that is still doesn't work. There has to be something else that is causing this issue. When it is at full throttle and the choke is all the way out it starts to billow black smoke, when it is less than 5/6 out it just surges and will keep running but just continuing to surge up and down. If the throttle is lower and the choke is pushed in the engine will just die. It also seems there is no way to adjust this carb? Please help

Thanks,
Tyler

Tyler,
Did You Remove The Welch Plugs And Clean Through The Two Or Three Small Holes Here? If Not That Is A Start. To Remove The Welch Plug(s) Take A Sharpened 5/32" Punch And Pierce The Plug. Do Not Over Do This As You May Puncture Through The Welch Plug And The Throat Of The Carb. Then Pry It Out Of The Hole. When You Replace The Welch Plug Use A Small Punch That Is Blunt On The End And Place The Tip In The Center Of The Welch Plug And Strike The Punch With A Hammer. Then Take Some Clear Fingernail Polish And "paint" A Coat Around The Edges Of The Welch Plug. I Know This Sounds Odd, But The Clear Fingernail Polish Can Withstand Contact With The Fuel Somehow And Give You The Good Airtight Seal You Need Here. Don't Use Colored Fingernail Polish, It Must Be Clear. Also, Did You Get All Of The Jets Out Of The Carb To Thourougly Clean, If Not Do So.