Stihl MS250 too much compression

[ghost1]

Ok folks, I'm stumped. Neighbor brought me his Stihl MS250 complaining that it tries to pull his arm from socket when starting. After initial pull on rope (which feels like vapor lock on cylinder), saw will start on second or third pull. Choke cannot be used even when engine cold, or flooding occurs. The following have been addressed.

1. saw has new carb
2. flywheel has been removed and key inspected. (there is some play when flywheel on shaft (nut not attached)
3. tank and oiler vents are operating
4. exhaust has been removed and spark arresting screen checked (clean)
5. piston/walls checked.. no scarring
6. with exhaust, carb removed, and spark plug installed, still feels like too much compression in cylinder

Anything else that might be checked?

 

[z71mike]

Got compression numbers?

 

[ghost1]

no, afraid I don't have equipment to test

 

[VA-Sawyer]

How does it feel with the spark plug removed?

 

[CapitaineHaddoc]

Put a solder in the sparkplug hole, turn the flywheel until the piston touch the solder, then measure the solder. Looks like a saw without base gasket, and too little squish...

 

[SilverKing]

my 250 did the same thing,had to start it with no choke.Take the plug out,crank it the motor and see how much gas spews from the cylinder.Mine would blow out way to much.I had to adjust the metering lever in the carb,no problems after that.

 

[ghost1]

pulls with little resistance, similar to my farm boss

 

[redfin]

Is the top of the piston clean?

 

[old-cat]

My one and only MS250 was a kicker to start it but that was the only problem. What worked with my MS440 kicking problem should also work with that one.
Get the flywheel loose, turn it clock wise against the key and torque it back down. That retards the spark so it don't kick.

 

[watsonr]

The flywheel is loose? If that is true, I'd suspect that the timing is off and why it's ripping the cord from your hand. Make sure the keyway is lined up correctly and tighten the nut down good and tight. Make sure the crank taper is clean and the flywheel taper also.

Check the metering lever in the carb and verify low and high needle settings.

 

[ghost1]

It was metering lever. Being new carb, wasn't looking that direction...

Thanks to all

 

[farmer steve]

educate a non mechanic. what and or where is the metering lever.? i have a ms 250.

 

[AVB]

educate a non mechanic. what and or where is the metering lever.? i have a ms 250.

The metering lever OP is talking is in the carburetor and it operates the fuel flow needle valve via the diaphragm motion. When it set too high it will cause the carburetor to flood out and sometimes even hold the needle valve open flooding the engine while it sits.

 

[AKDoug]

Of all the Stihl saws, the MS250 is the toughest to start in relation to it's size. It is significantly tougher to pull over than an 024 or the new 241. I wouldn't go messing with the carb expecting to cure the issue unless you have obvious signs of flooding when trying to start.

 

[MnSam]

Put a solder in the sparkplug hole, turn the flywheel until the piston touch the solder, then measure the solder. Looks like a saw without base gasket, and too little squish...

That is not really possible with this particular saw unless someone has done some serious mods.

Of all the Stihl saws, the MS250 is the toughest to start in relation to it's size. It is significantly tougher to pull over than an 024 or the new 241. I wouldn't go messing with the carb expecting to cure the issue unless you have obvious signs of flooding when trying to start.

I kind of agree. The 250 I just went through requires a determined pull, but does run very well.

 

[SilverKing]

Of all the Stihl saws, the MS250 is the toughest to start in relation to it's size. It is significantly tougher to pull over than an 024 or the new 241. I wouldn't go messing with the carb expecting to cure the issue unless you have obvious signs of flooding when trying to start.

I agree,but no choke to start a cold saw is a dead give away that its carb trouble