MS260 chicken or egg

[njm]

Yes I thought that

 

 

 

OK

 

Yes I'm surprised it was not noticed earlier but the guy is very conscientious, just slipped up a bit on the clutch sprocket but I can understand some reticence to change parts because it's a ballache trying to get spare parts approved by the accounts department. I wonder how long the spark plug was loose and I reiterate would the piston wear and touching the head have been the cause of the spark plug coming loose or the weak mixture from air sucking past the loose plug being the cause of the piston wear?

 

 

The thing is I am not a fan of frequently checking the plug and they don't come loose for no reason, so if it hadn't been checked recently...

 

 

 

 

 

However Is it worth 20 quid for a meteor piston and an hour's time to put it together or and a couple of hours' time to run a pressure test?

 

Personally i would rebuild a saw that had suffered a failure like this .

 

Loose plug or fueling issues / saw running very hot with vibration from piston causing plug to become loose / poor quality fuel / plain worn out saw run at max rpm for extended periods ..

Edited September 26, 2016 by njm

[Stubby]

Stubby I don't understand that, sure it has reduced on the exhaust side and slaps around plus one can see aluminium build up on the plug, piston, head and exhaust port but no signs on the inlet side. There is a slight recent scratch on the inlet side and a "polishing" mark on the ring lands by one transfer port which I took to be from the triangle of aluminium from the piston skirt being sheared as it left the crankcase. The piston inlet side is just worn smooth from long use.

 

It didn't go bang and despite the rings being stiff in the grooves they were not gouged and the saw actually still ran. Most I get back are horribly seized, either because someone was sloppy with adding oil to the fuel or mostly from someone tweaking mixture a bit lean, a problem I should not see with the MS261CM.

 

Incidentally has anyone else had problems with the FS460C EM with the carb and engine management/ignition module failing just after one season, and in our case a few days after warranty expiry. The fitter told me, on the side, they had had a number refused for warranty claims which required ignition unit and carb at £250 because they would not pick up from tickover.

 

When I said "When it goes bang" I meant when it fires ......

[openspaceman]

 

Personally i would rebuild a saw that had suffered a failure like this .

 

Loose plug or fueling issues / saw running very hot with vibration from piston causing plug to become loose / poor quality fuel / plain worn out saw run at max rpm for extended periods ..

 

I don't think it would be economic; cost of piston, bearings, gaskets plus 3hrs?? of time.

 

I have decided to put it to one side and either cannibalise it for bits or maybe rebuild it as a retirement project if I don't find part time employment, if I can take it with me.