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Before I started this project, all worked well with the primer. It would draw from the gas tank, fill the bulb and discharge back to the tank with ease. The engine would start, but would only run with the chock 3/4 engaged, then not at all as it heated up. There are no adjustments on the carburetor. So I went about to clean the carburetor, a walbro wyl-167 carb (MTD 753-04296) with GUM-OUT CARBURETOR + CHOCK canned pressurized carb cleaner. All cleaned up well, but after reassembly, the primer had trouble. It would pressurize, but it would not let the pressure return to the gas tank. After a bulb push or two, it would pressurize hard enough that you could no longer push the bulb in. I would expect that the return valve / flapper was stopping it, but I did not move any of the gaskets internal to the carb that make up the passageways and one-way valves, just squirted cleaner through the holes and passages.
Upon diss-assembly a second time, the internal, button type, rubber/noeprene check valve, (not the flapper check valves), seemed soft and mushy and the insert flange portion tore off with very little pressure, almost none.
Has anyone had problems with carb cleaner deteriorating the rubber / neoprene parts that form o-rings and such inside of a carburetor?

Troy built TB425CS with four stroke engine.
Thanks Rex

Sounds like you had it hooked up backwards...

But yes, certain carb cleaners are rough on small engine plastics/rubber. One time I primer the trimmer to try to start, and the foam air filter started to grow, like a marshmallow in a microwave. When it stopped growing, it would fall apart if you touched it.

No parts were disassembled on the initial disassembly, only the three major blocks were separated. The button valve was not moved, but carb cleaner was squirted through it. No individual parts could have been assembled backwards since it was never disassembled.

I was meaning the fuel/return lines mainly, some units can be easily mis-routed. But yes, those carb cleaners are very aggressive, which is why I rarely use them anymore, as most carbs just need dis-assembled, the dirt blown out of the, and
if the diaphrams are brittle, a new kit. If they are totally scummed up with 10 year old gas, I rarely waste my time, as the
price of a new kit plus my labor should be more than just slapping a new carb on with 15 minutes of my time

Fish said:

I was meaning the fuel/return lines mainly, some units can be easily mis-routed. But yes, those carb cleaners are very aggressive, which is why I rarely use them anymore, as most carbs just need dis-assembled, the dirt blown out of the, and
if the diaphrams are brittle, a new kit. If they are totally scummed up with 10 year old gas, I rarely waste my time, as the
price of a new kit plus my labor should be more than just slapping a new carb on with 15 minutes of my time

Click to expand...

Fish
Thanks for the info. I bought a new valve today and while there, talked with one of the local mechanics. He agrees with you about the harshness of the cleaner on plastics and rubber. He used the example of the inlet valve gasket on a regular BS engine. He says in carb cleaner, that very small gasket seat will swell to 3 or 4 times it's size.
One more experience to add to my collection, Don't use carb cleaner on plastic/ rubber! I'll bet it isn't so friendly on paint either.

I've used carb cleaner to take a clear cote off a mower so I could repaint it

Re: Does carburetor cleaner effect/deteriorate rubber carb parts? success :smile:

Great news;
I installed the button one way valve (check valve) internally in the carburetor this morning after fishing out the broken off end that had swelled. It snapped in with on trouble. Put the carb back together and installed it on the engine. Primer works perfectly. started on the first pull. took a minuet or two to warm up , then ran as if it were new.
Thanks Everyone. I hope this might be of help to someone in the furture
Rex