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Hello all. I'm new to this forum. Thanks in advance for any help. I have a Troy Bilt riding mower TB30R. The B&S engine is 21R7070039G1. Power Built 10.5 gross HP 344 cc. The mower is a 2015. Here is what happened. My son tried to start the mower last week and the starter engaged but wouldn't spin. I thought I needed a starter, so I ordered one and installed it. Still would not spin. I did notice that there was a gas leak from the carburetor area. Could not identify where it was coming from. I removed the spark plug, and fuel (with an oily film) poured out. I cranked the engine, and of course it spun easily. It was Hydro locked. Spinning the engine pushed all the fluid out of the engine. Put the plug back in and it started. Lots of white (maybe blue) smoke. It ran for about 20 seconds and died. It did restart, again with lots of smoke and then died again. Ordered a new carb and installed it. It was hydro locked again, so I removed the plug to clear the fluid. Put in the plug and it started. The smoke was there for only a few seconds and then it went away. After about 20 seconds, the smoke came back and the engine died. I could start it again, but there was still smoke, and the engine died within 10 seconds. I pulled the oil dipstick and the 'oil' was very thin and had a strong gasoline smell. My guess is a cracked block or head. I'm not sure how the guts of these engines work, so forgive me if i got the terminology wrong. Can it be fixed? Do I need a new engine? Maybe a block? Thanks again.

Spinning the engine does not push all of the 'fluid' out of the engine. There is probably nothing wrong with your block and head. The problem is probably with the needle valve and/or seat in your carburetor. Best to replace with OEM parts in your OEM carburetor.

In old days, there was a fuel shutoff valve installed on gravity fed fuel system. You can install one if none is installed now, and keep it closed when you're not using the engine. They only cost a couple bucks.

cpurvis,

Thanks for that advice. I did replace the carburetor this morning. I was thinking the same thing about the needle valve. With the new carb, that shouldn't be a problem. I also have a fuel shutoff valve between the fuel tank and the carburetor. My concern is the gasoline in the oil 'pan', and the oil that was mixed with the gasoline that was ejected from the spark plug hole. I would love for the issue to be a simple fix.

be sure to drain and refill with clean oil.

Good idea. Will do.

NA5KAR said:

cpurvis,

Thanks for that advice. I did replace the carburetor this morning. I was thinking the same thing about the needle valve. With the new carb, that shouldn't be a problem. I also have a fuel shutoff valve between the fuel tank and the carburetor. My concern is the gasoline in the oil 'pan', and the oil that was mixed with the gasoline that was ejected from the spark plug hole. I would love for the issue to be a simple fix.

Click to expand...

It is about as simple as fixes get. The fuel in the oil is coming from the carburetor overflowing into the intake manifold. If you replaced the OEM carburetor with an eBay carb, your assumption that the needle valve and seat in the new carb will fix the problem may not be good. OEM carburetors aren't all that good anymore but the dirt-cheap, aftermarket carbs are a more hit-or-miss than the OEM's.

Make sure the fuel shut off valve works and use it.

When you have done the oil change, run the engine for a few minutes then engage the blades
If it bangs, pops etc for a few seconds before settleing down turn the mower off and remove the dip stick
If there is smoke rising from the dip stick tube that confirms a blown head gasket, as does the rough running when PTO engaged.

cpurvis and bertsmobile1, Thanks so much guys. Sometimes, I get stuck on a potential complex diagnosis and I don't see the simple solution. I will change the oil today and follow your advice. The new carb is an amazon deal, but I do have the gas shutoff valve installed. I will definitely use it from now on. I'll let you know how it goes.

NA5KAR said:

cpurvis and bertsmobile1, Thanks so much guys. Sometimes, I get stuck on a potential complex diagnosis and I don't see the simple solution. I will change the oil today and follow your advice. The new carb is an amazon deal, but I do have the gas shutoff valve installed. I will definitely use it from now on. I'll let you know how it goes.

Click to expand...

When I finish using any mower or blower I turn off the fuel supply valve and let the engine run dry. I've done this for years and my carbs are like the Energizer bunny.