Gas going into crankcase - Motorcycles

Probable crankcase leak... most likely the crankshaft seals, but can be crank case seal or head to case seal or all. Web search "stihl chainsaw crankcase leak" for help.

Unfortunately the comprehensive tests for a crankcase leak is not a simple task and involves significant disassembly. Get a visual on the crank seals and go from there.

It could be your mechanical fuel pump on the side of the engine. Sometimes the diaphragm ruptures, and gas goes into the engine and into the crankcase that way.
If gas is going through the carb and into the oil, that would have to be way too much gas going through the carb and into the cylinders and then washing down into the crankcase. It is possible, but engine would run rough from having too much gas going through, and not being burnt, but washing down the cylinder walls.

Gas in your crankcase is typically a sign of carburetor floats not set correctly. They allow too much fuel into the bowl which then overflows and goes into the cylinder and leak down past the piston rings and into your crankcase.

This sounds like it is an older vehicle with a cam driven fuel pump mounted to the block. If so the fuel pump is bad and leaking fuel into the crankcase.

check the float in the carb,, the over flow of fuel is going straight down the crankcase breather tube attached to the carb , a stuck float will result in what your describing

When the float in the carb sticks, it allows fuel to drain into the cylinder, that runs pass the rings into the crankcase. When the crankcase is full the pistons cannot go down, and the starter won't turn the engine. Drain all the oil gas mixture, and refill with proper oil. Replace float, needle and seat in the carb bowl. Throughly clean fuel passages, and bowl. If motor won't turn, remove spark plug and turn over engine a few times to remove gas oil mixture from the cylinder too.

compression rings sound gone letting fuel into crankcase and filling up oil level, check compression and oil level

The gas is going into the the crankcase. When the piston goes down it opens the ports and allows the gas to go down untill it could fill the crankcase. Start by blowing compressed air into the spark plug hole and allowing the piston to go to it's lowest position. This will usually remove any liquid gas from the crankcase. Next get yourself a small spray bottle and fill it with the same gas mixture your trimmer uses. Now you can spray a small amount into the spark plug port, replace the spark plug, full choke and pull till it pops. set to half choke and pull. I have also sprayed into the carb but you must open the throttle to allow the gas to enter the combustion chamber. Spray,close throttle,pull choke and pull. You may need to do this a few times for it to start. After it starts let it run at half choke for awhile until it warms a bit then open choke and go to full throttle. If this dosen't work it's possible to have other problems.

it seems to be a fuel related problem. the gas should not be going into the crankcase. It is leaking into the crankcase . The fuel system is somehow leaking into the crankcase because of excessive flooding, or other fuel related problem like a gasket . don't drive the car like that.

I'm gonna go with theory #2 sort of. My guess is that one or more of the float valves is leaking causing the gas to overflow into the crankcase. This happens often with bikes that are allowed to sit for long periods with gas in the carbs and tank. A thorough fuel system cleaning is what it needs. I'd say go ahead and buy four carb rebuild kits for it - may as well since you'll have to disassemble the carbs to clean the gum and varnish out, which is really the best thing for it at this point. I wouldn't try to run it again 'til you get the carbs to quit leaking, the fuel drained out of the crankcase and put fresh oil in. ,,,