372xp won’t start.

[spudulike]

Difficult to tell but in my experience, the most common issues on saws and other hand held two stroke kit is the fuel system probably followed by seizure but this is less common now with limit caps, rev limited coils and auto-tune.

Your machine is pretty old and with old machines, it is common to have a load of old issues, typically wear and abuse from not being regularly cleaned and serviced.

A lemon would consist of major cylinder damage and a REAL lemon would be a bent crank or failed big end. I have only ever seen one 372 with a blown crank and that was from a US ported one where the impulse line came off mid cut and it detonated. I did manage to get it back together again for a reasonable cost - secondhand OEM crank etc. The top end was perfect - shows a bit of porting does protect the engine.

[adw]

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? 

[Craigb]

7 hours ago, adw said:

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? 

Maybe I didn’t put enough in. I only poured a drop in. Literally a drop or two out of a pipette

[Muddy42]

Have you tried putting a drop of mixed fuel in the spark plug hole rather than the inlet on the carb side?

 

As others have said a massive air leak can stop the fuel being transferred. With an older saw, you should pressure and vac test before spending proper money.  Although often confused, a pressure test is NOT the same as a compression test.

[spudulike]

21 hours ago, adw said:

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? 

It may have already been flooded, the spark plug may be oiled up, the OP may have bunged too much/too little fuel down the hole. 

I usually stick a squirt of GT85 or WD40 down the throat of the carb, that usually fires most times.

Most people don't work in our sort of environments and posses our diagnostic skills so things we do and get the effect we need/want, sometimes just don't happen when tried....look at the compression test....the times people buy an eBay special for cars and big engines and get a poor reading.

[Craigb]

Wd40 didn’t get it to fire and neither has fuel down the spark plug hole. This is what initially lead me to looking at the coil, which does produce spark. I’ll take the fly wheel off to make sure the keys aren’t shafted.  I’m not a small engine specialist but I am a welder with a sound knowledge of basic mechanical principles, hence the reason for my questions on this forum. The previous two saws I’ve rebuilt run well, it’s just the lack of even a fart of a start that has got me puzzled. I’ve tried two different plugs also. 

[spudulike]

Has the saw run with the aftermarket kit on it - you can see if the piston crown has carbon on it. If there is plenty of crud around the coil and the saw has run in its current state then it is probably the fuel system. Flywheel keys do shear but it isn't that common. You often get a few backfires or severe kickback when a key goes.

Personally I would have whipped the carb apart, cleaned and inspected it and more often or not, that would get it running. 

You can often tell from adjusting the carb if the saw is leaking air but it does take some experience to spot.

It takes a BIG air leak to stop a saw firing completely - I once had one with no seal on the clutch side and it still ran....badly.

Make sure the carb screws are out 1 1/2 turns each, they should end up at around 1 turn each once a final tune is done.

[Craigb]

The new pot and piston that is on the saw is brand new with no carbon on the top of the cylinder. I need to set some time aside to do a leak test which I should be able to do this weekend. 

[Craigb]

The last 346 I did up burped into life momentarily even with the pot loose.  

[spudulike]

50 minutes ago, Craigb said:

The new pot and piston that is on the saw is brand new with no carbon on the top of the cylinder. I need to set some time aside to do a leak test which I should be able to do this weekend. 

Ah, OK, very difficult to tell what the issue is then. All you can do is to do the leak down test, fit the new piston and cleaned up cylinder, check out the fuel system and go from there. 

When you try to start it, don't use the decomp valve. The extra compression in not using it will help the machine fire.