M12 starts to stall on bumpy terrain

[ScottR 5]

Hello all,

I have a 1995 312-8 that I can't seem to get right.  This motor runs fine when mowing flat ground in high 1st.  When mowing the field behind me that is mostly grass but rougher it starts to stall in the bumpier areas.  Traveling in second gear is even worse to the point where I can't use the tractor to spread seed and fertilizer.

 

It did this to me all last year so I used my 314-8 in the field and occassionally mowed the yard with the 312-8. It would still try to stall at least once when mowing a coupleof  bumpy spots in the yard. Towards the end of the year I pulled the carb, removed the bowl, jet screws and the large welch plugs, soaked it in parts cleaner overnight, ran a small wire in every tiny hole I could find, sprayed it down with carb clearenr and blew it out with compressed air. I made sure the float was parallel to the bowl. After that  It ran like a champ for my last mowing and fertilizing outings. It didn't stall on rough ground at any speed.

 

This year it's back to it's old tricks.  I drained the carb, gas lines and tank before storing it. I use ethanol free gas. The plug and gas filter are new. The gas lines are 2 years old.  I suppose I could pull the carb again and try soaking it in lacquer thinner, and maybe even try opening those small welch plugs (don't really want to) but before doing that wondered if anyone had thoughts on what I should do?

 

Thanks for any advice.

Scott

[Phatboy 565]

I would replace the jets in carb,, and buy some "sea-foam" and start engine and pour a tiny bit in carb while running and put in gas per instructions ,, that should fix ya up,, 

[pfrederi 18,707]

Did you replace the float needle valve?  Is there any chance of gas in the float.  There is a spec for setting the float. closed and open.

 

[ScottR 5]

Thanks for the replies guys.

 

I didn't change the fuel inlet needle (I think that's what you meant pfrederi) because the original had a neoprene tip that looked in good condition and the replacement had a metal tip. I guess I can try the replacement needle. Thanks for the specs on the float, i'll check that too (after I try the SeaFoam-maybe I'll get lucky).

[N3PUY 1,031]

I had a similar problem .... on rough terrain I would bounce off the seat and that would make the engine want to shut down.  (seat safety switch)  Even on a side hill I would lose pressure on the seat.  I'm not convinced that your problem is fuel ....  maybe a loose wire or faulty safety switch.  My 416-8 with the Onan did it also but that was the 9 pin connector.   My C125 spit and sputtered and then quit when the wire fell off the spark plug .... the little cap on the plug unscrewed inside the plug wire ... something you can't see until it falls off completely.

[953 nut 60,246]

I'm with @Phatboy on this one, running good last fall and running like crap now after setting; a double dose of sea-foam in the first tank of gas will clean it out and you will be in good shape. Could be a seat switch or wire like @N3PUY said, but my money would be on fuel sloshing inside a slightly compromised carburator. 

[ScottR 5]

Ok guys, thanks for all good ideas to chew on. I'll start with the Sea Foam once we get out of this darn cold snap.

[can whlvr 994]

sure sounds like a float issue to me

[sorekiwi 761]

Another thought, I have a 310 that doesnt have the rubber baffle thing in the top of the float bowl.  (The one that was in there had all distorted and wouldnt seal right so I left it out).

 

That tractor stumbles over the bumpy parts of my yard, places that all my other tractors have no problems with.

 

I probably should put one in sometime.

[953 nut 60,246]

10 hours ago, sorekiwi said:

rubber baffle thing in the top of the float bowl.

That could do it for sure.

[ScottR 5]

My M12 and M14 both have Walbro carbs, WHG 52 and WHG 60.  Neither has the baffle in the top of the bowl.  I can't find a parts diagram for either carb.  Did the Walbros use baffles?

[953 nut 60,246]

According to this reference the Walbro carbs wit brass floats have the baffle, see page 13. I know that my 312-8 has it.

 

[ScottR 5]

Thanks for the great reference!

 

I think that page 13 (3.5)  is for the Kohler 1" carb parts listing that begins on page 12 (3.4). It looks like none of the Walbro carbs in the reference have baffles and they all have plastic floats like my Walbro 52 and 60.

[ScottR 5]

Reporting in:

 

Phatboy, 953 Nut and pfrederi had the diagnosis correct. A new inlet jet needle and a double dose of Sea Foam has her running perfectly, at least so far.  I've put about 5 hours on the motor and things looked good before the starter took a dump. It just spins without engaging the flywheel. Luckily it died after I parked it in the shed.  I'll look at it this weekend. I've read several threads on this problem so I think I know what to check.

 

Thanks again guys.

 

Scott

[can whlvr 994]

ya for the starter you may just need to clean the shaft and spring on the end,then apply some sort of dry lube,if you r lucky it will need cleaning only

[ScottR 5]

It's kind of strange. Removed the fly wheel cover and the shaft, gear and spring looked real clean.  Sprayed it down with carb cleaner and applied dry lube. It works fine now.