201 not starting hot

[Westphalian]

Hi, I bought a used MS201 CM a few years back for limbing. it no longer starts when hot. Because the starter rope pulls fairly easily I checked compression which was 1500, the cylinder had slight scoring but I am no expert. I took the opportunity of giving it a deep clean and retuned the carb and at home I thought I had sorted it but obviously on site after one tree it wouldn't restart. After a google, people are saying fuel filter, spark plug, vapour lock or ignition module. Can any wise person put the possibilities in order of likelihood so I don't waste too much time and money?
Thanks

 

[Mad3400]

I had the same experience and the issue turned out to be the wiring to the switch were damaged.

Mad3400

 

[cscltd]

Saw with scored cylinder or piston will be hard start when hot.
If it is a mtronic saw, Use choke (triangle) position for hot start may help

 

[Sidecarflip]

Sounds to me like boiling fuel and vapor lock. Years ago I hade a miserable Poulan that did that and I offed it. Scored jug isn't helping it either.

 

[stihltech]

1- pull the muffler and check the piston. Then you will know.

 

[Westphalian]

Sounds to me like boiling fuel and vapor lock. Years ago I hade a miserable Poulan that did that and I offed it. Scored jug isn't helping it either.

why would that happen?

 

[Westphalian]

1- pull the muffler and check the piston. Then you will know.

I did. The piston wasn't spotless but as I really didn't have much experience looking I checked the pistons on my other saws and they were similar so I figured just ordinary wear, esp as the compression was 150 which google told me was just about acceptable for the 201

 

[stihltech]

Yes, that is good compression. Now we need to know if there is spark when it won't start. This is where an inline spark tester is very useful.

 

[Stihl Learning]

Carb solenoid!

 

[lone wolf]

I did. The piston wasn't spotless but as I really didn't have much experience looking I checked the pistons on my other saws and they were similar so I figured just ordinary wear, esp as the compression was 150 which google told me was just about acceptable for the 201

How about a pic of the exhaust side of the piston before we assume it's good.

 

[Westphalian]

Carb solenoid!

could you please expand on this as although I am keen to do it myself I am not a mechanic.

 

[lone wolf]

could you please expand on this as although I am keen to do it myself I am not a mechanic.

A small electronic component on the side of the carb they cost around 30 - 40 dollars.

 

[stihltech]

Now check for spark when it won't start. An inline spark checker is very useful at that time. If I know there is an issue, I will install it and run the saw until it happens.
Did you try opening the fuel cap and reinstalling to see if it would restart. Verifies a vent issue.
Try the easy, no cost things first.

 

[Westphalian]

How about a pic of the exhaust side of the piston before we assume it's good.

that is an excellent idea but unfortunately when I had the housing off and the manifold removed I didn't take a pic, just observed

 

[lone wolf]

I'm not convinced the piston is good yet! OP, pics?

 

[Westphalian]

Now check for spark when it won't start. An inline spark checker is very useful at that time. If I know there is an issue, I will install it and run the saw until it happens.
Did you try opening the fuel cap and reinstalling to see if it would restart. Verifies a vent issue.
Try the easy, no cost things first.

I have a spark checker so will use it when the saw is hot, probably weekend

 

[lone wolf]

that is an excellent idea but unfortunately when I had the housing off and the manifold removed I didn't take a pic, just observed

The muffler side is what really shows damage, if you saw some light damage on the intake side, it is highly likely to be scored heavier on the exhaust side.

 

[Westphalian]

The muffler side is what really shows damage, if you saw some light damage on the intake side, it is highly likely to be scored heavier on the exhaust side.

yes I checked the muffler side as I didn't have a great view via the spark plug opening even with a cheap endoscope I bought for the job. it's good for checking for wax in may ears though.

 

[lone wolf]

Well try a new Solenoid then it's cheap enough and good to have anyway.

 

[Westphalian]

Saw with scored cylinder or piston will be hard start when hot.
If it is a mtronic saw, Use choke (triangle) position for hot start may help

it's not mtronic