MS261C will not start

[PhillH]

1 hour ago, spudulike said:

So, has the machine run with the old coil on it?  Has it run at all in your ownership? 

Sometimes you get some pretty weird issues when a saw has passed through less able hands and had someone else do some less educated repairs on it. I have seen machines have the wrong coil AND flywheel on them...that was a really interesting one!!

I would check the coil black wire goes to earth and the red wire has continuity to the solenoid. If that red wire is broken, you will get some strange running issues.

Yes, my dad has owned this saw for the last 6 years and never had a problem until now. It does not get abused and only really gets used in the winter. 
 

Thank you for the wiring tips, I will check on those 

[Stubby]

11 hours ago, PhillH said:

Yes, my dad has owned this saw for the last 6 years and never had a problem until now. It does not get abused and only really gets used in the winter. 
 

Thank you for the wiring tips, I will check on those 

When you say " only gets used in the winter " does it sit for months with the same fuel in ? I know you said you have tried fresh fuel but the carb could be gumed up from stale fuel , even have water in the float bowel as happens with ethanol additive in modern pump petrol .

[PhillH]

2 hours ago, Stubby said:

When you say " only gets used in the winter " does it sit for months with the same fuel in ? I know you said you have tried fresh fuel but the carb could be gumed up from stale fuel , even have water in the float bowel as happens with ethanol additive in modern pump petrol .

It probably gets used once/twice a month through the summer. It’s been in use a couple of times a week since September with no problems.
 

I would have thought if it was a fuel or carb issue then it would have attempted to fire from fuel going directly into the plug hole or brake cleaner through the air intake. Spud also mentioned that too.

 

Thanks everyone for your help, have a Merry Christmas 

[peatff]

On 25/12/2024 at 07:32, Stubby said:

even have water in the float bowel as happens with ethanol additive in modern pump petrol .

They don't have float bowls Stubby😉

[Stubby]

2 hours ago, peatff said:

They don't have float bowls Stubby😉

Ok . the bit with the diaphragm and the metering arm .

[spudulike]

I have given a lot of saws a shot of GT85 down the carb and if this is done with the throttle open and the saw is pulled over with the throttle open, the saw will run up with full revs for around 1 second and then die. This will even work if no carb is fitted!!

If the OP opens the throttle, sticks some easy start, WD40, GT85 or similar down the back end of the carb and then pulls the saw over with the throttle open, it should roar in to life if the rest of the saw is working OK.

If the saw has good compression and ignition/spark/timing is OK, it should fire up for a split second by doing the above.

The baffling thing is that if the rest of the saw is OK, why isn't this working.

Have you tried swapping the plug over? They don't often go bad but it can happen.

[PhillH]

16 hours ago, spudulike said:

I have given a lot of saws a shot of GT85 down the carb and if this is done with the throttle open and the saw is pulled over with the throttle open, the saw will run up with full revs for around 1 second and then die. This will even work if no carb is fitted!!

If the OP opens the throttle, sticks some easy start, WD40, GT85 or similar down the back end of the carb and then pulls the saw over with the throttle open, it should roar in to life if the rest of the saw is working OK.

If the saw has good compression and ignition/spark/timing is OK, it should fire up for a split second by doing the above.

The baffling thing is that if the rest of the saw is OK, why isn't this working.

Have you tried swapping the plug over? They don't often go bad but it can happen.

Hi @spudulike thanks again for your response. Christmas has been busy so not had any more time to look further.

 

Had swapped the plug for brand new and swapped back to the old a few times just to try it, spark is viable with both. 
 

I have tried two different types of brake cleaner just incase, I have also sprayed it on the floor and lit it with a lighter to check it ignites. 
 

I have took petrol from the tank and put it straight in the plug hole, neither petrol or brake cleaner makes a difference even with the throttle wide open.

 

My next steps are:

Check continuity on wiring harness from beginning to end.

Take off the exhaust and rock fly wheel to see if there is any movement in the rings.

Check compression tester on running saw to confirm the 125psi I get on this saw

 

If non of the about show any results then it will be a good clean down and take the cylinder off.

 

Hopefully I get a hour or two over the weekend to take a look. 
 

Thanks again.

 

[GarethM]

Then it's the timing if it's not igniting when you've chucked brake cleaner in the cylinder.

 

Even with crap rings you'll get a burn but only if it's sparking in the right time 

Edited December 27, 2024 by GarethM

[PhillH]

30 minutes ago, GarethM said:

Then it's the timing if it's not igniting when you've chucked brake cleaner in the cylinder.

 

Even with crap rings you'll get a burn but only if it's sparking in the right time 

I pulled the flywheel off and key was in tact where is should be. How else could the timing be out? 

[ChrisNewport]

Does it spark with the original coil on but not fire with fluid in the plug hole? Scoring to the piston isnt always on the exhaust side. Id pull the cylinder.