Small Engine Generator

[NHGenMan]

Hi - my name is Phil. I am working on converting a small engine. <5hp to propane from UL gas. I built a new carburetor and can get the generator to start. After it warms up, the engine oil starts to flow out of the vent port that was attached to the old carburetor. I am sure that the oil pan is not overfilled and have filled it slightly below the capacity of the oil pan.

What is causing this? It does not happen when I am running UL Gas. It almost looks like the oil is absorbing some gas and expanding. Is this possible?

Thanks for your input.

 

[theoldwizard1]

Briggs and Stratton 5 hp flat head ?

I am guessing that the "vent" port is just for crankcase ventilation. If the oil level is correct, worn piston rings will cause excessive pressure in the crankcase and that can cause oil to come out the vent.

There is usually some kind of "filter" that restricts the amount of oil coming out that vent.

 

[The Cobbler]

too high an RPM and/or bad rings are worth an honourable mention

 

[nadogail]

Welcome to the forum from Southwestern California.

You may be due for an engine inspection. Can you test the compression?

 

[theoldwizard1]

Briggs and Stratton 5 hp flat head ?

On the old flat head the valve cover/breather assembly (B&S 791779) captured excess oil and returned it to the crankcase.

 

[NHGenMan]

Thanks for your reply. This is a cheap sportsman off brand inverter generator, 800w running capacity. I am converting it to propane and installing an electric start. I think the propane is causing the piston pressure to rise too high and it is blowing past the rings. The generator is new with very little run hours on it. I don't think it is a wearing issue. I am thinking of putting putting filter on the vent line that will restrict the flow.

The oil coming does look like it was churned up by gas. If I totally blow it up, not much invested so that's ok. I will have to buy a better brand that has already been converted.

 

[Wrench97]

You built the carb or bought a conversion kit with a fuel lock off and propane vaporizer assembly?

 

[NHGenMan]

I built a manifold where I mix air and propane upstream of the engine fuel inlet. I have an air valve that controls the amount of input air. The engine runs great until the oil streams out of the vent line. That is what I am confused about.