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Discussion Starter · #1 ·
After mowing for a good hour or so, my MF 16 just up and quits. It's got the K341 Kohler. Replaced carb (Walbro) back at the beginning of the season. Seems as though this issue started after that. Old carb had badly worn throttle shaft, so I replaced the whole carb with a new one. Also the points, condenser, coil, and spark plug have been replaced this season. After working for an hour or so it just losses power and quits, no backfire or anything else, just powers out and dies. Anyone have an idea? Thanks, Bill.
 

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I had a similar problem on a Briggs engine once that ended up not having enough float drop. After about an hour of mowing on a hot day it would quit. Found out if I pulled the choke half way I could keep it running a little longer. Finally traced it to the float not allowing the needle valve to open far enough and when it got hot it evidently swelled enough to keep the needle shut. Bent he tab to allow it to drop more and problem fixed. May be a problem in your new carb.
 

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I also had a similar problem with a K341 but mine would die after only about 10 minutes. Let it sit for awhile and it would restart and run for a couple of minutes and die again. Turned out it was trash in the carburetor. Took the carb apart and cleaned it, put a fuel filter in the gas line, and I've had no problems since. Good luck.
 

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When it dies, does it still have spark and compression? If it does, then you have a fuel problem. If not, fix the spark or compression. I would also look at the vent in the gas tank cap. When the engine dies, see if there is a vacuum in the gas tank. If the fuel line is getting too hot youmay have vaporlock. Good Luck, Rick
 

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Discussion Starter · #6 ·
Sprint 6, yes it does have a fuel pump. Has the Kohler plastic replacement fuel pump, but its at least 15 years old by now. But would not the fuel pump either work or not work? Don't understand how it could be the fuel pump after about an hour of working fine.
 

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I had a similar experience on my JD 120 with the K301. Did complete tune-up and it would run for 30--45 mins then die. I eventually figured out it had a bad coil that would short out when hot. After it cooled for 10-15 mins it would start up and run until it got hot again.
 
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Just came inside from mowing. It shut down again after about an hour. Touched the coil and its pretty hot, can only touch it for barely a second. Disconnected the small wires from both sides and ohmed it, 4.5 ohms. Checked the old coil I took off a few months ago and it ohmed at 1.5 ohms. Maybe after the thing cools down a bit I may swap coils and see what happens.

Update,,,swapped coils and still the same problem. Coil still gets pretty hot, don't know if that's just the way they are, or if both coils are no good?
 

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Could be the metal expansion is tightening up the valves enough to dump the compression. Valve adjustment would cure it if it's that. Kinda sounds like this could be your problem. My nephew Craig just called & having similar issue.
 

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Discussion Starter · #10 ·
Got on the old MF16 yesterday morning and it would not start. Checked spark and looked pretty weak. Got me a brand new Genuine Kohler coil this time and installed it. Started right up and ran well. Hour or so later would not keep running. Was 93° outside air temp.
 

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For all the world, that sounds like vapor lock.
Check the routing of the gas line and make sure the hot air isn't blowing on it or its up against something hot.
i would agree with this. Does this one have a fuel pump on it?
 

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As others have said, check the float setting in the carb. I just put a rebuilt K321 in MF14 and when I went to start it the first time it would hardly run at and idle and this was with a new carb. Took the carb off cleaned all the passages, reset the carb settings and now it takes off and runs like it should up to full throttle.
 

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Yes, it has one, but he said 15+ yrs old.

Bypass and run a gravity tank for a while to test?
I guess my reading skills are lacking today. I would try the bypass/gravity feed approach as a way to test.
 
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Discussion Starter · #16 ·
Yes, I will try bypassing the fuel pump and run the fuel hose straight to the carb. The gas tank is actually just slightly higher than the carb on these machines so maybe it will feed itself okay. Question-- I thought that the whole idea of the plastic fuel pump as oppossed to the original metal body pump was to avoid a vapor lock condition-- is that not so? The fuel hose is ¼ inch rubber on mine, no steel anywhere. The hose is routed the same way since original in 1975 and isn't up against anything particularly hot.

About checking the float setting in the carb, would that make a difference only when hot? Need to find the spec on that too, its a fully adjustable (high & low speed) Walbro.

Way too hot to mess with it today. I'll report back in a few. Thanks!
 

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Discussion Starter · #17 ·
Update, bypassed the fuel pump and ran the tractor with the gas being gravity fed to the carb. It ran okay as long as I kept the tank full but then after about an hour would quit, just as before. It would seem that this would rule out the fuel pump. Removed the carb and checked the float level. On this particular carb the manual doesn't give specific measurements but rather states that with the carb inverted (bowl off) that the top of the float (actually the bottom) should be parallel with the carb body at the bowl seat. It looked pretty close to parallel, maybe just needing ever so slight of an adjustment, which I did. There is no "float drop" adjustment on this one. Spray cleaned the carb and reset the base low and high speed mixture adjustments. Installed the carb onto the tractor and reattached the fuel hoses back to the fuel pump. Went to work with it and it seemed to run well, then up and quit after about an hour. Acts like its out of gas when it quits, but there's plenty of gas.
 
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