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You will be able to see the bearing cages by removing both crank seals, easier than splitting the crankcase if the bearings look ok.

I think the saw needs to be completely dismantled before you even consider fitting a new cylinder, it’s a mark 1 machine, not sure what you paid for it but this is not going to be a cheap repair, can you return it ? how was it described?

You may well have issues in the bottom of the engine, possibly main bearing cage broken up as there are some groves on the transfer port side of the piston skirt.

What you have there is an ingress of something very abrasive, this has scored the inlet skirt of the piston, and also removed the nikasil coating around the inlet port( as seen by the shaded area around the port ) this now requires a cylinder and piston. where and what have you been cutting?

It realy depends on the age of the saw, however to go through the changes, remove the hose from the breather , this will stop fuel vapour entering the filter elbow, dont forget to blank the the conection on the filter elbow, next if the fuel hose is clipped into the induction manifold remove it and shorten the hose, re connect to the carb ( you will need to turn the the carb inlet connection ) this will take the hose away from the heat of the cylinder, if the saw is a G model remove the the heater pad sandwiched between the carb and the filter housing, open up the cylinder cover on the right hand side ( not in the carb side of the cover or this will stop the centrifugal air cleaning ) remove the the deco valve and fit the blank, get it connected to common service tool and reset the carb settings, if the saw has an orange frame air filter try to obtain a yellow frame filter, the orange framed filter id very very fine and even though looks clean can be blocked, this will cause auto tune to lean off and run too lean, finally pressure test and compression test, any loss of compression will affect the idle. It goes without saying basic maintence should be adheared to, cleaning any clogging in the starter housing grill or between the cylinder fins, never use stale fuel, replace the fuel filter regularly. On rare occasions i have loaded the 555 firmware onto them.

I assume that means it’s going, glad to hear it.

I do hope it just fires up and away it goes, but with a drop of fuel down the inlet, and a spark it really should have at least popped, but please prove me wrong by telling us she is running tomorrow.

Not convinced.

Couple of old farts together I guess.

So it is a clamp shell design, the main bearings are supplied sitting inside a carrier which also incorporates the crank seal, you can buy just the seal and carrier but to try and press the bearing into them is a real pain in the ass, the cylinder is sealed to the crankcase with gasket cement, so machine apart , new bearings with seal and re seal the bottom end, as the crankcase/ oil tank are composite check the area where the bearings sit, if there are signs of melting or distortion you could have bigger issues trying to seal it, there should be no need to put seal ent around the bearing carrier.

As I recall the Zara was the EPA carb from the 365, very difficult to tune due to it being a low emission carb.

Not really a lover of Stihl, however L& S have always been a good source of parts when I have touched the, my experience with those Chinese carbs has been bloody terrible, a good friend on here gave me good advice, and it was always far better to rebuild the original carb, accelerator pump is the first port of call on the carb, sling the Chinese carbs as they will send you round the bend trying to tune them, the roller bearings used on these machines will always give you end float, so quite normal. Over to Spud now.

I think it is a chain saw Steve, it could be a 254, or a 345, or anything I guess, if it is a 345 as you know it’s a clam shell design and the bearings sit inside the seal.

There should be a very fine o ring under the sleeve, they all, and should have it.

I agree, that is not enough leak to stop it firing up, I have been trying to find what the 02 ignition unit fits but am struggling, the 01 does fit the 576 but does not appear in any 372 parts list, there has to be a very simple reason why this machine does not fire, I am begging to think this may be an ignition unit issue.

Oh yeah of little faith, have to rush the Archers are on the radio in a minute

It sounds like the fan on the end of the motor touching the outer cover or the conduit holding the motor wiring, could be a twig in there

Well done sir, the 10mm spark plug helicoil is not easy to get fitted correctly.

The dealer doesn’t have a clue, deco valve 503715301, rubber boot 537180001, clip 537320901.

The only sure way is to replace the crankcase.

Fuel starvation would be my guess, so still has blockage in the carb, split inlet boot/ impulse tube, fuel filter in the tank blocked, low cylinder compression .

Stubby is absolutely correct, the manual deco valve will fit in place of the valve in the cylinder, you then blank off the nipple from the bottom of the cylinder, either a rubber boot or use a self tapping screw and sealant.

I still cannot get my head round why when primed with fuel down the inlet it does not as least fire once, unless it actually did?

I get duff information every day of the week. Ive been using these machines for years, and my father before me I mix all the fuel myself I buy the best oil money can buy I have twenty other machines running on the same fuel i read the operators manual every night before going to bed It must be a Friday night machine I know my rights etc etc.