Carb for MF 85

chas036 · May 30, 2018

I just completed installing my head after having a complete valve job done on my 85, and it started right up and runs real smooth. My problem is it will run for about 1 to 2 min, and then start to sputter and stall. I can start it back up with the choke , but it will continue to sputter and stall. Now if I let it sit for 30 seconds or so, and then start it up, it will run great for about a min or two that start to sputter and stall.

I took the fuel line off and there is steady stream of gas to the carb. I took the carb off and blew out all the passages and put in a new float valve. and still I have the problem.

When I had the carb off, I noticed that it was a TSX 670 , but the parts book says I should have a TSX 786 or TSX 644. Could this 670 carb be causing me the problem because it is not correct?

old · May 30, 2018

Pull the carb drain plug and make sure you have a good steady flow of gas that will fil a pint jar in less then 3 minutes. Also is your spark a good blue/white and jumps a 1/4 inch gap or more?? Are the valve set correctly

ptfarmer · May 30, 2018

That carb like most of the MS carbs have a brass 90 degree elbow that the fuel line screws into. You should be able to unscrew that elbow, once the elbow is off there should be a screen. Wouldn't be surprised it that screen is clogged, and just need a cleaning.

chas036 · May 30, 2018

I took that elbow off and I didn't see any screen attached to it.

Ncnative · May 30, 2018

I had/ have a similar problem on my 135, almost identical symptoms. (You can read about it here on this forum “MF135 gas, I’m starting to hate this tractor”) First follow the advice of others about confirming fuel flow thru the carb by checking how much flows out of the carb drain. If you have sufficient flow then you may like me have an electrical issue. My problem is an intermittent spark or lack of spark being caused by the 12v going to the coil is dropping out. I disconnected the original coil wire an patched in a wire directly from the battery to the coil now my 135 runs like a to.

2tractors · May 31, 2018

Check the float. It could be rubbing the sides hanging closed. Condenser and coil.

ptfarmer · Jun 1, 2018

(quoted from post at 19:27:10 05/30/18) I took that elbow off and I didn't see any screen attached to it.

Some one either replaced it with a different one, or they removed it. Should have looked like this.

chas036 · Jun 1, 2018

I FOUND MY PROBLEM! I tried the 3 min gas flow as suggested here and saw that it took almost 5 min to fill a pint out of the bottom of the carb. I then I started working backwards on the fuel line. I disconnected the line from the carb and still had a slow flow. I disconnected the inline filter and guess what? All of sudden I had a torrent of gas.

When I bought the tractor, I tested the flow before I started working on it , and it was fine coming out of that filter. So when I took the tank off to do my valve job, and then put the tank back on, I never thought of changing the filter. The tractor doesn't have a sediment bowl. It has 45 degree elbow in the bottom of the tank going to a ball valve then going to a inline filter.

I think when I removed the tank, I disturbed all kinds of rust and sediment in the tank, so when I reinstalled it , all that sediment clogged up the filter. Anyway, I changed the filter, and the tractor run perfect now.

old · Jun 1, 2018

If it was me I would install a sediment bowl like it should have on it and throw that in line filter as far from the tractor as I could. Most in line filters are made for fuel systems with a fuel pump so they need more pressure then a gravity flow system has so they clog up real fast and then you have the problem you have had.

Carb for MF 85

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