MS261C will not start

[PhillH]

Thanks @Stubby @woody paul I did have a poke at the rings and they seemed to move but given the fact we have a spark and fuel it leaves only one thing as you both say.

 

I will check the compression tester on a running engine just to confirm it is ok.

 

The saw needs a good clean before I strip it down so it might be a week before I come back with a update.

 

Thanks again

Edited Monday at 20:21 by PhillH
Corrected

[spudulike]

125 is low if measured on the correct gauge. It is worth comparing to a good running saw as I have seen enough measurements made with car type gauges. The difference is a car cylinder shifts A LOT of air and the gauges use a schrader valve (like a bicycle inner tube valve) with a much higher spring rate. The gauges for small engines have a much weaker spring in the valve and measure much higher than car gauges so, please check on a decent machine.

The lower ring looks a bit gummed but the piston looks decent so it isn't too bad. Sometimes if you rock the flywheel to and forth very slightly, you can see the ring is free in the groove.

Just to clarify, the coil the saw always ran with....is it the same part number as the later one and you have tried BOTH coils on the machine with the same result? 

I have seen the small Mtronic wires shear and this can cause all types of issues so worth doing a continuity check from where they start and where they end. You may have to get creative with a needle or similar to get to the contact but worth checking. 

The fact a bit of easy start wont give it a burst of life means it is unlikely to be a carb/fuel issue.

Did you have the flywheel off to check the key?

[PhillH]

1 hour ago, spudulike said:

125 is low if measured on the correct gauge. It is worth comparing to a good running saw as I have seen enough measurements made with car type gauges. The difference is a car cylinder shifts A LOT of air and the gauges use a schrader valve (like a bicycle inner tube valve) with a much higher spring rate. The gauges for small engines have a much weaker spring in the valve and measure much higher than car gauges so, please check on a decent machine.

The lower ring looks a bit gummed but the piston looks decent so it isn't too bad. Sometimes if you rock the flywheel to and forth very slightly, you can see the ring is free in the groove.

Just to clarify, the coil the saw always ran with....is it the same part number as the later one and you have tried BOTH coils on the machine with the same result? 

I have seen the small Mtronic wires shear and this can cause all types of issues so worth doing a continuity check from where they start and where they end. You may have to get creative with a needle or similar to get to the contact but worth checking. 

The fact a bit of easy start wont give it a burst of life means it is unlikely to be a carb/fuel issue.

Did you have the flywheel off to check the key?

Hi @spudulike thanks again for your extensive response. 
 

I will check the compression over Christmas with another saw. I understand what you are saying regarding the two types of compression testers. 
 

I have had the flywheel of and the key is fine and still in tact. I will have a look at rocking the flywheel to see if there is movement in the rings. 
 

The coil I removed has the markings 1141 4700 C

The new coils is marked with 1141 4701 D (the packaging says 1141 400 4732)

I did give L&S engineering the serial number and this is the part the recommended 

 

Both coils have the same issue, I did a continuity test between each section but need to do beginning to end.

 

With the throttle wide open I am getting plenty of smoke with every pull, when I remove the plug I am getting smoke coming from the plug hole so it is definitely trying to fire.

 

Thanks again for your help

[Stubby]

8 hours ago, PhillH said:

Hi @spudulike thanks again for your extensive response. 
 

I will check the compression over Christmas with another saw. I understand what you are saying regarding the two types of compression testers. 
 

I have had the flywheel of and the key is fine and still in tact. I will have a look at rocking the flywheel to see if there is movement in the rings. 
 

The coil I removed has the markings 1141 4700 C

The new coils is marked with 1141 4701 D (the packaging says 1141 400 4732)

I did give L&S engineering the serial number and this is the part the recommended 

 

Both coils have the same issue, I did a continuity test between each section but need to do beginning to end.

 

With the throttle wide open I am getting plenty of smoke with every pull, when I remove the plug I am getting smoke coming from the plug hole so it is definitely trying to fire.

 

Thanks again for your help

Hard to tell for sure from just a photo but that coil to flywheel gap looks tight , touching even ....

[Welshfred]

Check manifold for air leakage, they do split after time. A good (gentle) poke around with a torch and a screwdriver should reveal any splits. Or, esp if your anti vibs are worn, the manifold can disconnect at either end. 

Edited yesterday at 08:38 by Welshfred

[PhillH]

2 hours ago, Stubby said:

Hard to tell for sure from just a photo but that coil to flywheel gap looks tight , touching even ....

Thanks @Stubby I moved it in to see if it had any effect on the starting issue. I will put it back when I do some more investigation.

[PhillH]

9 minutes ago, Welshfred said:

Check manifold for air leakage, they do split after time. A good (gentle) poke around with a torch and a screwdriver should reveal any splits. Or, esp if your anti vibs are worn, the manifold can disconnect at either end. 

Thank you @Welshfred I will take a look at that. 

[Welshfred]

I might be thinking more of the 260, the 261 is a bit different in design, esp anti vib wise. But I imagine that manifold is still a potential weak spot that could affect starting...

[openspaceman]

42 minutes ago, Welshfred said:

I might be thinking more of the 260, the 261 is a bit different in design, esp anti vib wise. But I imagine that manifold is still a potential weak spot that could affect starting...

I thought the big difference engine wise was the 261 is a stratified carb with two choke tubes whereas the older 260 was conventional.

[spudulike]

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.