8n runs for 45 minutes, then surges under load

Milesvdustin · May 13, 2016

195p 8n sidemount. New rebuilt and cleaned carb. Rebuilt governor. Idles at around 420 rpm.

Tractor runs amazing until about 45 minutes in on the bush hog. It will start to surge and try to die real bad. If i turn off the hog, it runs perfectly fine.

Any ideas? Im lost!

Milesvdustin · May 13, 2016

Forgot to mention:

Clean fresh gas i just bought today.
New Autolite 437 plugs properly gapped .025.
12v converted with an alternator (bought this way)

Den N Ms · May 13, 2016

Milesvdustin,It could be the vent on the gas tank is plugged up,causing the surging under load after 45 min run time.Loosen the fuel cap the next time it does it.It may need a vented fuel cap or vent the one you have on it by drilling a 1/32 hole in the cap and put a cotter key in the hole.

Milesvdustin · May 13, 2016

Took some pictures. The points screws do not look right. The points look a little dirty, they dont have a brown rub block.

The part where the shaft fits in here looks a bit worn. The tabs inside the distributor cap are arc burnt a little and the corners are eroded.

Lots of dirt and junk inside the distributor

The firing order counterclockwise on this cap is the top wire is 1, then 2 4 and 3.

Milesvdustin · May 13, 2016

I Iabeled this picture.

brucew44guns · May 13, 2016

I had that problem for 2 summers---think I finally figured it out. I too drilled a hole in gas cap, and put a cotter pin in, so it could breathe. No dice. The tractor would be running just fine, and suddenly act like it was about out of gas, bucking and jerking. Finally recently,. I took off the sediment bowl, opened valve to where I usually do, and noticed a pitiful small stream of gas, no way enough. So I opened it 3 times as much as usual, probably about all the way. Got a good stream. No more bucking and jerking afterward. Now that is brilliance--very high tech solution!! That darned thing got me so upset at times, a simple matter of opening the fuel shut off valve a bit more. Try it---

howdy1960 · May 14, 2016

Open fuel shut off 2 full turns only, if needing to open fully as only a trickle of gas comes out it is time to remove sediment bowl assembly from tank and clean it. Opening fully results in running off the reserve and may cause someone to walk home from field to get more gas instead of driving back.

Milesvdustin · May 14, 2016

I pulled the sediment bowl apart last week when i did the carb. ]

R Geiger · May 14, 2016

Do you havae the little spring tab that goes on the shaft before the rotor goes on?

Milesvdustin · May 14, 2016

Does that tab hold the dust cover down? It is there.

Anyways, i left everything as is and went mowing. At 40 minutes or so it started surging again. I grabbed my wrench and the cyclone air cleaner jar and checked fuel flow. It was a weak trickle at best.

This wont let me load pictures right now but i opened the fuel shutoff all the way and the fuel increased fourfold. I mowed for 4 more hours like that with no issues.

I did notice i had a good amount of smoke coming from the breather. But i also have 110+ psi on all cylinders cold when i did the check. Should i do an atf or mmo treatment?

R Geiger · May 15, 2016

It sounds like the stand pipe for the main fuel flow is partially plugged. The clip is needed for the rotor to fit right, it is needed whether there is the dust cover or not.

Milesvdustin · May 16, 2016

Does the long tab on the clip point up or down towards the dust cap? Right now it points up and the ring around the shaft is on top of the dust cap. Rotor fits loosely.

R Geiger · May 16, 2016

The long tab points up, I don't think you could get the rotor on with it the other way.

8n runs for 45 minutes, then surges under load

Milesvdustin

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