MS261C will not start

[Stubby]

1 hour ago, PhillH said:

Sorry mate @Stubby

No worries bud . Only in jest 😁

[spudulike]

The basics are that combustion needs fuel, compression and spark but life is never that simple, the spark needs to be timed and the fuel needs to be metered correctly.

The saw should fire up with a squirt of easy start down it and typically rev up for half a second before dying. 

Compression should be over 150psi measured on a small engine compression gauge and not an automotive one. The gunson hi gauge should give you a correct reading as others will.

It sounds like the saw is firing but not starting, the easy start should get it to run for a very short time and if this isn't happening, the fact the spark is good leads me to low compression. Have you pulled the muffler off to look at the piston? 

 

[PhillH]

Thanks @spudulike tomorrow I will do a compression test to rule that out. I have had the muffler off and cannot see any scoring. 
 

I will try something else instead of brake cleaner too. 
 

It is very bizarre as I can see smoke and hear the change in note.

 

I shall report back tomorrow, thanks again to everyone 

[PhillH]

6 hours ago, woody paul said:

Had similar problem with a big husky brush cutter, you have doneexactly the same thing I did. 

Anyway turned out to be stuck piston ring, but it felt like good comprestion when you pulled it. 

Probably worth popping cylinder off and having a look. 

Cheers @woodypaul I have a few things to look at tomorrow 

[PhillH]

6 hours ago, Dan Maynard said:

Do you know what fuel he put in? I'd say start with basics if you haven't already - pop the exhaust off and check the piston for scoring. Also change the plug, could have a crack or other fault.

Cheers @danmaynard I know the fuel is ok because he had been using it all day and it went in the replacement saw. I have had the exhaust off and all looked ok but as woody said to check for stuck rings. Hopefully a compression test will tell me more. The plug is new, swapped that with the new coil.

Thanks for you help 

[peatff]

Did he put chain oil in at the same time as he refilled the saw ? Sounds like a mix up to me, I did it once and had to strip the carb to ungum it.

[PhillH]

2 hours ago, peatff said:

Did he put chain oil in at the same time as he refilled the saw ? Sounds like a mix up to me, I did it once and had to strip the carb to ungum it.

No mate, fuel was ok and I have put fresh fuel in to rule it out too 

[PhillH]

Compression test is 125psi

Still will not run on carb cleaner

Put new coil on and closed the gap

Checked the loom 

 

Could it be the rings? 
 

We have spark, air, fuel but compression feels good, and it wants to run. We are getting smoke

 

[Stubby]

1 hour ago, PhillH said:

Compression test is 125psi

Still will not run on carb cleaner

Put new coil on and closed the gap

Checked the loom 

 

Could it be the rings? 
 

We have spark, air, fuel but compression feels good, and it wants to run. We are getting smoke

 

Compression needs to be 160 + really to support combustion me thinks .

[woody paul]

Second picture shows your problem, I would say lower piston ring is stuck. Exhaust port looks a bit carbed up.