ouch said the piston

[Dilz]

So took this ms200t apart today as a part of my teaching myself about how to fix stuff project.

 

Not sure what caused it - but its a new piston for sure.

There is some damage in the crankcase where what i guess is the bit of skirt that drop off has gouged into the metal a bit - Figure i can get away with smoothing that down with a dremel and some wet and dry - or is that not going to work? I notice some soot or something like in the crankcase - is this normal?? (pics below)

 

Also - due to my location getting parts for stihl is a nightmare - i ususally get stuff from Ebay - but does anyone have any recommendations for ebay sellers selling new pot and a pistons - lot of ships from hongkong on there - though if those parts will work ok then thats cool - but they are a bit too cheap....

[EricBradley]

Ive never seen damage like that to a piston, looks like inlet side. There will most likely be a a foreign body in there somewhere. As for ebay parts, the majority of the bits the uk sellers sell on there are from china aswell, they import it by the container full.

[spudulike]

I had one exactly like that, it was the closing catch on the air filter cover that one side of the screw had broken off and dropped down the inlet side. I would check the cover screw and also make sure the bit isn't lurking in the exhaust or in the bearings.

 

Smoothing the bruise in the port is probably fine - just run the new piston up it to make sure it moves smoothly.

 

Also make sure the small and big end bearings are OK, inspect the big end cage carefully as if this is damaged/cracked, it will spit out bits that will wreck a new piston.

 

I would go Stihl or Meteor on the new parts.

[kinderscout]

To me, looking at the damage it looks like one of the needle bearing has come from some where.?

[Dilz]

I think spud has it. There is a bur on the inlet where the bit of the screw must have hit. Its been bugging me what it was that caused it. Will make sure to check it. Is there a decent method of cleaning the bearings incase any small bits of chewed metal have worked their way in or a is it better not to risk it and just replace them?

[spudulike]

I usually use a bit of carb cleaner and GT85 then blast them with the compressor and once good, the compressor will turn the bearing using air pressure - just oil it after before reassembly.

 

It gets them really clean.

[Dilz]

Thanks. Next question...for the oiling after reasembly. Should I use something specific? All my saws are run on aspen (swedish rules) in case that makes a difference.

[spudulike]

Thanks. Next question...for the oiling after reasembly. Should I use something specific? All my saws are run on aspen (swedish rules) in case that makes a difference.

 

I was saying use a little oil on the bearings and bore DURING reassembly just to start the saw off before the oil in the fuel takes over. It will burn off within minutes so it doesn't really matter too much what the oil is. I tend to use car engine oil but can use two stroke or similar.

 

Aspen is fine, just make sure you tune the L screw a little rich on the bottom end as they like it that way.

[pike]

Just check price for genuine parts,they have reduced price on some by quite some margin on a few models,

[Dilz]

managed to have a check on the airfilter screw and yup - there are bits busted of the back of the screw so 100% certain this is what caused it.