312-8 Running rich fuel coming out of air filter

[MAD MARK 74]

For those who read my posts know that I have ran into many issues so far with my "new to me" 312-8. Fixed the mule guard rubbing issue. Fixed all my bad pulleys, found out that a spindle had bad bearings and changed them out. Was able to figure out my year of tractor and fixed a few mechanical issues there. Now that I got it up and mowing I mowed half my yard yesterday and went to mow the other half when I let it idle for a minute while I got another beer. Upon getting back on I hit the throttle all the way up and realized I was only mowing the front half at about 75% throttle. So, I kept the throttle up to full and was only to mow 2 strips before the tractor was choking itself out. Pulled over shut it down and could see gas pouring out of the air filter/carb area.

 

Came inside and did some research on here and see that many people have had this issue and it seems their posts go no where. Some talk about floats, which I took off and it seems fine, others talked about adjusting idle and fuel screws but those seem alright too. So I went on to the mow the last half at 75% throttle and everything was fine. Any idea why cant go 100%? 2nd gear at 75% is a little too slow and 3rd gear is too fast for mower deck to cut at 75%. Ive included a picture of my thottle linkage as I had that off and am not sure if its put back on correctly causing an issue.

 

 

 

[Retired Sparky 526]

I'd maybe ck the float. While you in there area, ck the settling bowl (for dirt) under the carb.  If you see dirt, it may keep the float from closing.

[WHX?? 46,637]

21 minutes ago, MAD MARK said:

when I let it idle for a minute while I got another beer.

See there's your problem take enough out to finnish the lawn or get that drive thru fridge set up!!

 

I woulda suggested the float but if that was the problem one would think it would be alt all throttle settings. I don't think the mixture screws would be so far out of wack as to let that much gas go thru. Any chance the choke is partially closed? If you have to take the bowl off again double check that float seat & valve & main jet.

[wallfish 15,871]

Your linkage looks correct.

If gas is coming out of the TOP section of the carb (above the bowl), the problem is definitely the float or needle valve or both. When they are working properly and set properly, gasoline can not get past that valve except when the fuel in the bowl is lowering, which allows the float to move down and open that valve. Fuel lowers in the bowl from being sucked into the engine for ignition or the bowl is leaking.

 

When you say "It seems fine", can you explain everything you checked?

You'll need to remove the entire carb from the engine to set the float. You can find all the information in the manual for engine concerning the carb. Be sure to give that float a shake and listen for fuel inside of it too, which means it has a hole in it and will not float to the proper level if it does.

You'll need to flip the carb over to set the float height. Also a good idea to connect a piece of clean hose to the fuel inlet and try to blow air through that valve with the carb flipped over. You should not be able to blow air through it if the valve is sealing properly.

 

Edited March 24, 2016 by wallfish

[MAD MARK 74]

I guess I will need clarification on some terms. I thought taking out the float bowl I was able to check it there. I didnt know I had remove the whole carb. I did not do that. The bowl seal seemed alright and I cleaned the dirt at the bottom of the bowl. There was a lot. I checked the plug and it was sooty black like a rich condition. I had to let the air filter air dry because the prefilter was soaked as I could wring out gas from it.

 

I read another thread where this guy was having the exact same issue...but never really says if he got it fixed or not.

 

Im not ready to take off the carb yet without the proper gaskets being close by to put it back on. Like I said it mows and runs great at 75% throttle and Im headed back to work for a week. Ive read that these have governors was thinking maybe the previous owner screwed up the limits somehow and its dumping gas in. He did put a new throttle cable on.

[wallfish 15,871]

The carb will need a good cleaning also since it was filled with crud.

It's just about impossible to thoroughly clean the carb, check and set that float with it still attached to the engine.

Governor has absolutely nothing to do with fuel spilling out of the carb. It's controlled by that arm which has the link directly to the butterfly on the carb.

Just about the only thing that causes that condition was explained above. I'd suggest you download the manual which will help guide you through some of the procedures when you are ready and of coarse, you can always get help on here too! .

 

[WNYPCRepair 1,875]

I have a C165 the PO said did the same thing, but I haven't had it running long enough to duplicate it yet. 

Everything I found while searching for an answer was also related to the float or needle valve sticking. If you had dirt in the bowl, I bet that is your issue. 

[Phatboy 565]

I would say the float also,, and check the jets in carb for a blocked up jet cause that can cause fuel to build up in the bowl and come ot the emultion tube...

[MAD MARK 74]

Looks like ill research the gaskets and seals needed for such a job and go about doing that my next few days off in 2 weeks. Thanks.

[WH nut 553]

I would check to make sure the choke isn't walking its way closed. Not as uncommon as you would think.

[WNYPCRepair 1,875]

Would a weak spark cause this? 

[puddlejumper 67]

Check the atmospheric vent, it is a small air passage that should be above the float in the bottom of the carb that will come out just inside the throat of the carb or to the outside of the carb. If this air passage is clogged it causes a high barometric pressure inside the fuel bowl caused by the pressure of the fuel being pumped in which in turn will cause the float to have less buoyancy than it would under normal or balanced  atmospheric pressure. this normally causes the engine to flood immediately with fuel pouring from the carb and the engine will not run. But maybe yours is just partially obstructed. I soaked and cleaned a carb many times a few years ago to no avail when a member on here suggested this to me and sure enough I had missed this orifice every time so look close.

 

[wallfish 15,871]

Hey, @puddlejumper is back!

[MAD MARK 74]

Just an update on this and my issues. After swapping out rear end fluid then finding out my left wheel seal leaks when correct level I trouble shooted my carb issue.

 

I bought a new carb off of eBay and installed that. The tractor ran horrible. I adjusted the needles and couldn't get it to mow more than 2 strips before over gassing itself. So, I installed the old carb back on. Ran a lot better with the old carb. I thought the eBay carbs were supposed to be pretuned needle wise.

 

So, I can still mow the grass and use the mower but it seems that if I try to go full throttle gas literally comes out of the front of the carb and soaks the air filter and fouls the plug. This was with both new and old carbs. Was thinking about the float like some have mentioned but the new carb had the same issue. So, now what? Any ideas?

[MAD MARK 74]

Another update just to make sure the topic is full and complete for anyone actually using the search button.

 

I watched numerous videos and read a lot of stuff. Mainly this website...  http://gardentractorpullingtips.com/carbfuel.htm#adjustfuelmixture

 

I was able to go home and adjust my carb settings quite perfect. I also regapped the points which seemed off a slight hair. Maybe a .025. The tractor idles well now and has full power. Only mid range sputters a bit but the air filter and plug need changed. Mowed the whole yard (3.5 hours) and not once did it back fire or stall or spit gas everywhere. Now I have a newer eBay carb as a paper weight. Ive enjoyed working on this thing, now onto the wheel seal.

[Howie 882]

It does not matter where you get a carb trey will have to be adjusted. There are some preliminary settings to get it 

where it will start will need to be set for the particular engine it goes on..