Stihl MS180, low compression on new engine

[DaleCI]

I just installed a complete, new engine on a Stihl MS180. New carb, fuel line and ignition coil.
Engine is from Amazon seller. It seems to only have 75 PSI compression and won't even pop
on mix or ether. Has anyone run into this problem with the Chinese replacement engines? I've replaced
the top end on several Stihls with good results. This time, doing a complete engine, its crap.

 

[Chainmale]

Could be an automotive/non-small engine compression tester giving a false result. And/or could be an airleak somewhere, possibly the crankpan? As that wouldn't have been bolted up until you put it in the chassis

 

[DaleCI]

got a recommendation for a "small engine compression gauge" I've never had a problem with the gauge before...
How would the crankpin leak? Seals were in place when I got the engine out of the box.

 

[Chainmale]

The cover that goes around the bottom of the crankshaft is sealed and has 4 bolts holding it together.
I thought the 4 bolts that hold the pan on also bolt the motor to the chassis like the 025 series saws but looking at an IPL the MS180 has separate mounting bolts.
Is it getting spark and fuel?

 

[DaleCI]

Yup, spark from a new coil and fuel from a new carb. I even tried the old carb and same results.
Crankcase came totally assembled. Maybe just my bad luck with a poorly built new engine...what could
they do wrong?

 

[Bob Hedgecutter]

If you test another small engine with the same tester- what kind of a reading does the gauge give?
Like a known well running saw?

Engines from China= dubious at best quality- I mean they don't cost much eh? So you dont expect much.
But as you say- they come fully assembled and drop into the plastic cases on the 180- replace the 4 bolts that hold it there, put it together and away you go- for a short time usually before something goes amiss inside the cheap engine.

Willing to bet, if it sparks, is getting the correct air/fuel mixture to the combustion chamber and no massive air leaks- the timing is all to hell.
Either key on flywheel was never lined up on the crank, or nut was never tight enough and the flywheel spun and is now out of position.

 

[DaleCI]

I've checked and the key is in place and flywheel did not spin out of position. I've worked on many Stihls and
know how to assemble properly. This one has thrown me for a loop with such lousy compression right out of the box.

 

[Bob Hedgecutter]

Oh okay- well if you are experienced- the answer should be as plain as the nose on your face then.
One way to bump the compression is to remove the plug, pour a teaspoon or so of oil down the plug hole, swill it about a bit, replace the plyg and start the saw.

Also wondering if you are willing to shell out for Amazon engines- are you also using the TORCH or similar spark plugs?

 

[DaleCI]

Oil in the spark plug hole...been there, done that...no to Torch plugs..i like NGks.

 

[Bob Hedgecutter]

So you say oil temporary compression boost does not work, everything else is perfect and yet the saw still wont run?
Sounds like you are flooding it then- but let me guess- you have checked that and it is not flooding.

Pretty simple engines, correct ratios of fuel and air, compression, spark and timing of spark and they run.
So you are either experiencing some kind of black magic- or something simple and obvious.

 

[Bob Hedgecutter]

IF indeed, all the engine, intake tract and fuel delivery check out- via pressure/vacuum testing and such- is the muffler full of insect nests and or complete void filling of all the mesh in the spark arrestor screen blocked with carbon?