spudulike

If the fitted cylinder is OEM and not too bad, I would always try to salvage it and fit a decent quality aftermarket piston if one is available. Take note of Stubbys advice, no point fitting new parts until a vac/pressure check is done and the fuel system is checked out and adjusted correctly after fitting the new parts so the saw isn't over revving.

The roller I was talking about is the chain roller, not the mower roller.🙄

Typical seizes are using old fuel oil mix where the oils lubrication has been degraded, lack of or no two stroke oil in the fuel, air leak or running lean. Running lean can also include split fuel lines, blocked fuel filters, blocked gauze strainers etc The piston crown damage is interesting. It is possible that someone has damaged it using a poor choice of piston stop or it has caved due to the heat. The damage looks like a bad case of pre ignition but that could only happen if the coil had developed a weird fault or the flywheel managed to shear it's key and stop a few degrees in advance. Never seen one that bad before.

I had one of those once, the clutch centre had a clutch shoe retainer lug broken...exactly the same had occurred.

The chain side plates often have a number stamped on them and this can identify the chain type. If you can identify the chain, purchase a meter length and a link so you can make your own, usually by grinding the rivet off and then driving it out with a punch. The link can then be fitted with the closed end facing the rotation direction. Just done a Rover mower which was a 35 ANSI chain...cost around £12 for the link and enough chain for two chains. If you can't identify the chain type then it comes down to roller size, roller pitch (measurement between roller centres) and the width of the chain. Unfortunately, many chains are close in sizing.

I usually push them in as level as possible then tap them in with a suitable size socket as long as it can locate on the edge of the seal otherwise use a reasonable drift and hammer to tap it in. Just do it evenly and match the depth to how the original one was fitted - usually flush with the casing.

You have to know me to know what my words mean. A tad expensive = WTF, do I bend over so you can take me up the posterior, I will have to put the wife on the street corner to pay for that...you have to be having a forking laugh!!!

I do remember some of the yanks modding carbs but the 3120 is relatively rare so never really took much notice of the mod. I have heard of people fitting tights or socks over air filters when milling as the dust will cause wear on the inlet side of the cylinder, doing so will make the saw run a little richer but guess that will be a positive. The foam filter should help you.

The bearings die from lack of grease rather than not using the Stihl grease. Ensure all the grease points are located and filled regularly - weekly if using it every day. Those gears are a tad expensive!!!! Lithium grease is fine.

TBH, Forget all the timing figures but do ensure the saw holds pressure/vacuum and the fuel system is overhauled to ensure the saw doesn't go pop again. You would probably find a bit of a muffler mod and lowering the squish to 0.5mm will up the power but the carb has no adjustment on the H setting making mods a bit more difficult to get the best performance.

That seal is FUBAR, L&S are normally pretty good and will phone if the order is going to be delayed.

I would normally say it sounds like a bit of shyte in the carb gauze strainer but will assume that this was replaced in the carb overhaul. If your saw has stood empty and unused for a long period, it is most likely the fuel line has hardened and isn't reaching the fuel when on its side. You could fill the tank fully and see if it still happens or just replace the fuel line and filter as matter of course and it will probably fix your issue. It is possible the fuel line has a small split/crack in it but the above is probably the best option.

I think he meant the help line.....tough week....big G&T and ....relaxxxxxxxxx

The 340 has the top crankcase moulded in to the lower part of the cylinder making it a typical "Clam" type engine so modifying it with a 346XP cylinder isn't possible. The 350 however, has a separate metal moulding making up the top crankcase and this gives it a flat base where the 346XP cylinder can be fitted and is a known mod although I have never done this. Both the 340 & 350 have a plastic cradle that the metal parts are bolted to and the lower crankcase is formed by the plastic cradle. This IPL will show you what I mean: - 340_340Е_345Е_350.pdf

On the circlips with no tang orientation.....When you purchase an OEM stihl piston, there will be one circlip fitted and the open gap will face upwards to the crown of the piston and that is how I always fit this type of clip.