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Discussion Starter #1
My Murray model 38608x12c with a 12 hp Briggs 2281707-0415-01 engine dies soon after start. It started doing this about 20 months ago but I had moved and didn't really need a tractor so I stored it until now.

It starts fine, but then fuel seems to flow back into the carb from that other tube coming into the carb from the engine. Not even sure what that tube is. When that fuel comes rushing back, it floods the carb and the engine shuts down. I was told the carb needed rebuilt. I bought the kit and a machinist that I work with that does this, did it for me. I put it back on yesterday and the same exact problem happens.

I can do engine repair, but I'm a shadetree "auto" mechanic, so I am not so good on small engines, especially why this is happening.
 

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Old Iron......Forever
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I wasn't able to do a search for the model of the engine as you put it out....

The number may be needing to be checked again.....

As to the rebuild, and the flooding, it sounds to me like the float is stuck open. It has a breather tube if it is the soft rubber tube you are referring to. That isn't likely to have any gas coming from it....other than what is flooding into the throat. Or there is a possibility the needle valve seat is actually letting gas get by it, and the seat would need to be pulled and replaced with a new one. I've changed them when I didn't see any reason for gas to be getting by, but replacing it almost is the only way to assure that the leaking (flooding) is corrected.

Good luck

You can re-check you model number and go to Briggs website for a parts break down and get the parts numbers you need for your carb.
 

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Discussion Starter #3 (Edited)
See next message before replying to this one:

I had an extra 2 at the beginning. It's 281707-0415-01. The seat and needle are brand new as of 2 days ago when it was rebuilt.

And yes, its the black rubber tube that seems to have gas back flowing into the carb from the engine. It's possible that the gas floods into the carb because the engine is shutting down, but it seems that the gas comes flowing back thru that tube first, and then the engine starts to flood and die.
 

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Discussion Starter #4 (Edited)
I think I jumped the gun. Its running fine now. I put a new ignition switch in just now because yesterday it wouldn't turn over and I had 12v to the switch, so I just shorted across the solenoid to start it. So now with a switch it was much easier to start it and if needed, start it again as I played with the carb settings.

So what do the screw adjustments do on the carb? The needle valve screw I adjusted to get it running and keep it running was on the bottom of the fuel bowl. It looks like there is one on the top too. Is that high speed adjust or something?

Then the engine needed to blow out a lot of oil from all the previous times I've worked on it 20 months ago and once the smoke cleared, it seems to be doing good.

I didn't think about it but I had it up on my trailer and it was leaning forward at a 15° angle so that probably didn't help things, but after it ran awhile, I brought it down the level ground and put it away for today. I think I might have ran out of gas when I was working on it yesterday too and after it didn't stay running today, I put more gas in it. Too wet to mow so it'll have to sit for now.

As I was moving it I realized it has a steering problem I forgot about so I'll have to look at that next. The gear plate isn't close enough to that gear connected to the steering rod so it slips when I turn. I don't see any adjustment to move it closer yet. At least it doesn't have that crappy leather steering joint my really old Murray had.
 

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Old Iron......Forever
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That is great, and yeah, smoke clears usually and it is fine....

Good that you didn't have to jump into a carb rebuild again. After all, you had it done by your friend.

Bottom is main jet, adjust it from just closed, out 1 1/2 turns and fine tune from there.

Top one should be idle/air mix, usually it is also around the 1 1/2 turns out. Then to fine tune it, you adjust idle/air screw CCW till engine falters, adjust it CW until engine falters, noting while making the adjustments how many turns between the two positions. Adjust it to center of the two positions, and go CCW 1/4 turn. This should be just right for a throttle up to full speed from idle without faltering before going to full revs. If it does falter, you might have to adjust the main jet CCW a bit to get it to stop faltering on the the throttle up. These shouldn't be extreme adjustments, just very minute adjusts, will get it to be smooth.
 
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