MS660 flooding, filling muffler, and draining out tank overnight.

[Greenclimber]

A few months ago my saw stopped running. I had just gotten the saw 2nd hand. It wasn't very easy to get started in the first place. It was my first time using it. I was cutting small wood, nothing abnormal. I took the saw home and checked/cleaned the carbs and tried to get it to fire back up. Nope not happening. Had about less than half a tank of gas in it. So I set it down and a few days later came back to mess with it. However the tank was empty. Gas was running out of the muffler. Pulled the plug and pulled the cord a few times. It was like a spray bottle coming out of the hole. What's going on? No cracks or broken hoses.

The other day I messed with the saw again to see what was going on. Put fresh gas in it, pulled a few times, and gas is spraying out of the decompression valve like a fine mist/spray bottle. Okay strange. So I disengaged the decompression valve. However the compression still felt low like the decompression valve was still engaged.

So I checked the compression and at 60PSI I'd say that the engine is bad. Took off the muffler and the rings are toast. So I'll replace the piston and cylinder. Any thought besides that? I've never heard of the tank just getting sucked dry like that, and filling the cylinder and muffler with gas.

Thanks!

 

[Welder56]

Maybe the needle in the carb is staying open? Allowing gas to seep and flood the saw.

Setting the metering lever properly will solve that problem as long as the needle itself is in good shape

 

[redoakman]

+1 that ^

 

[Jacob J.]

Maybe the needle in the carb is staying open? Allowing gas to seep and flood the saw.

Setting the metering lever properly will solve that problem as long as the needle itself is in good shape

That's exactly what's happening, so in addition to at least needing the top end rebuild- he's going to need a full fuel system rebuild.

I would say this is also a good time to go through the bottom end with new bearings and seals.

 

[Bilge Rat LT 20]

If the diaphragm is installed wrong or the wrong one used it will flood the saw sitting in a hot garage.
If the gasket is next to carb body instead of the diaphragm it will leak. Heat will pressurize the fuel tank helping the gas flow.

If the wrong diaphragm is used the saw will flood sitting there. That will make you scratch your head untill you notice the proper new diaphragm sitting on the bench where your buddy just rebuilt his carb.

60 psi is bad. You may be able to clean up the cylinder instead of buying new.

X2 on the seals and bearings replacement.

 

[Greenclimber]

Cool, thanks everyone. Okay lets say I go as far as to split the case and replace the seals. I'm sure I'll need special tools. Is there a how-to video available for me?