Robins 25hp keeps cutting out

[bol4fun]

My muffler header pipe got a crack in it near 1st cylinder and completely fell off a few weeks ago so I had a friend do some fabricating and installed my son's concoction of a motorcycle muffler on it. It was working fine with no muffler but loud as ****. My son changed the oil and hydraulic filter the day before the fabrication and we drove it back on the trailer in a rainstorm and now it won't hardly run at all. Today, I took the muffler off....no difference.....took the air filter off....no different. Yesterday, it was at least somewhat running although as soon as it heated up a little, it would start cutting out a lot but today, I was lucky if I could keep it running a few minutes and then it would finally die. Next step is to spray some carb cleaner in the carberator (had some surging problems once after cleaning air filter and evidently got some dirt in the carb and the carb cleaner corrected the problem).
Anyone else have any suggestions? We obviously screwed something up. I will take some pictures of the muffler tomorrow.

 

[Marks481]

Could possibly be an issue with the fuel pump. It is a mechanical pump that uses pressure pulses from the crankcase to compress the diaphragm and pump fuel. It is mounted on the cylinder head, and maybe it got too much heat when you took off the muffler.

I have found that they don't like heat.

 

[MossRoad]

My Kohler melted the choke cable over the years to the point that I couldn't operate the lever. I'd cover the air intake with a metal cup, start the unit, get it running, and manually lift the cup a little at a time until it would run on it's own. Then after it warmed up, the choke cable would loosen up and I could move it again. Shut it off and let it cool, and the choke wouldn't operate again.

So that's one thing to check. Remove the air cleaner and see if the choke butterfly operates correctly with movement of the choke cable.

Also, the governor mechanism could be sticking. Spray the whole thing down (with engine cold) with carb cleaner liberally and manually operate the throttle and choke cables, and the governor levers, etc... to see if anything is sticking.

I don't know about Robin fuel pumps. My Kohler fuel pump was mechanical on one of the valve covers. It finally broke the diaphragm and new was ridiculous $$. So I removed it all and put a vacuum fuel pump on the unit for cheap $.

Another way to test the fuel pump is to look at the fuel level in the tank. If the fuel level is at or below the level of the carb, and the fuel pump is having problems, the engine will run rough or not at all, exhibiting symptoms of low fuel. Fill the tank up so that the level of the fuel is a couple inches below the top of the tank and see if the problem goes away. With the tank near full, it will gravity feed the carb and run fine until the level drops to near the level of the carb. That's how I figured out I was having fuel pump problems.... it would run rough an hour after filling the tank! Fill the tank, and it ran fine.

Anyhow, hope those things help out.

 

[bol4fun]

Thanks MossRoad .... I filled it with gas and then since the hood was up decided to look at the throttle and choke mechanisms to make sure they were working fine and low and behold.... I had a broken spring on what a carpenter friend said was the governor. He said a quick fix... we will just bend the end of the broken spring. Long story short is that he cobbled it up so bad, I now will be going online and ordering new spring and a part that holds the linkage to the carburetor made of plastic that he mangled to death. Oh Well... I was cringing the whole time he was cobbling. I should have done it myself. He is a framing carpenter and is use to others hiding all their mistakes with drywall.
Anyhow, should be good to go but not before the weekend when I need it. Here are a few pics of the muffler. I angled it up some since I keep it in the garage. I am sure I will crunch it sooner or later as many times as I back into trees but it will work for now.

 

[MossRoad]

Well, at least you found something. :thumbsup: :laughing: