spudulike

If you take the plugs out and turn the engine over slowly, you should see the piston rising to top dead centre (TDC) and both tappets on one cylinder rising to fully up so both valves are sealing for the compression leading to power stroke. At this point, make sure there is a small gap under each tappet by moving it up and down feeling for a small amount of play caused by the normal clearance between tappet and valve. If there is no clearance, the tappet needs backing off (the valve seat may also be damaged) or if the gap is massive, you may have a stuck valve. The fuel pump working wont prove decent compression. A reading of +/- 10 - 15 psi between both cylinders will prove that either both cylinders/pistons are shagged or they are OK. Not sure what reading to expect on mowers but 140+ should be OK on a cold engine. I would normally check the carb out, if the needle is leaking, it will cause flooding of the engine.

ADW......I think you mean a compression test...being a four stroke 😉. Not sure if the engine has an automatic decompressor for starting so you may get a low reading if it has. Much depends on the hours it has done etc, a lot of our diagnosis is done at a glance at the state of the unit.

I have never had one of these apart but in general, most engine issues of this type are fuel related so pull the carb apart, check that the needle valve is working, check the fuel is flowing in to the carb, check that the float bowl has fuel in it and there is no water or shyte in the bowl. Remove the main jet AND the emulsion tube - this may need coaxing and then ensure all the holes and main jet are clear. Blast some cleaner or brake cleaner through all the holes/channels and reassemble. I am making the assumption that the carb is like the ones fitted to most of the B&S single cylinder engines. Sometimes the needle jet seals against a tiny rubber O ring and these swell stopping the float being level once the carb is held upside down (Lowering the amount of fuel in the bowl) this can make an engine very lumpy...it did on my Intek engine and can be replaced if you have similar. One other thing to check is that the choke is sealing fully on a cold engine. This may be operated by a lever, thermal actuator or a throttle position but also worth checking as if the choke isn't sealing, cold starting will be hit and miss.

When a saw is new, the rings, piston and cylinder bore are microscopically rough and the piston, rings and cylinder are not particularly round and matching. When you first use the saw, you need to use this roughness to bed in all these components quickly so they form a close fit and this is done by using the saw hard for short periods of time but not for longer cuts that will produce too much heat and cause damage. You can actually hear this happen when you fit a new piston and lightly hone a cylinder as it makes a ringing noise on running. Failure to do this will mean that the piston components and the cylinder will never match perfectly causing less compression and therefore, less power.

If you are trying to start it on full choke, pulling it over many times, it will flood. Have you tried pulling it over whilst holding the throttle wide open? It isn't recommended as "normal" as it is dangerous but it may get a bit of life out of it. If the saw is flooded, remove the plug, turn the ignition off, point the plug hole downwards and pull the saw over a few times briskly until no spatters of fuel come out. Heat the plug up with a plumbers torch or kitchen job, if the wife is out, replace and use the starting method above but no choke. If a saw just pops after around 6 pulls on choke, even if it doesn't pop, turn the choke off as it will flood. See if this works. If you have a seriously big air leak, the saw wouldn't flood. If it was a small air leak, it would still run. What are your H&L screws set to? Is the idle screw holding the throttle valve open a bit and is the starting position holding the throttle open around 1/4 open?

You have learnt well Mr Stubby!

I would check which boundary hedges are actually yours if you purchase this house. Typically it would be the right side facing the house and possibly the one at the bottom of the garden. The deeds will have a "T" on your boundary and is the only definitive way of ensuring which hedge is legally yours. You would also be advised to talk to the neighbours as ripping out a hedge just after you have arrived may piss them off.

A real bad air leak = no fuel mix entering the cylinder so the engine doesn't start. A slight air leak = high idle speed, over revving at maximum revs. What are the symptoms you have again...is this machine flooding when you are pulling it over with full choke many times or just when the machine is left sitting there? On your first post, the saw doesn't start and then it runs but dies and also floods at sometime....a good diagnosis begins with accurate symptoms.

You tease the side of the gauze strainer up with the sharp point of a craft knife. Personally I would try adjusting the carb as I already stated before doing a full pressure/vacuum leak down test but you basically seal off the exhaust port, inlet port, impulse line (if it is a rubber pipe type), and use a modified spark plug fitting to let in air or evacuate it by way of a Mityvac tester or similar and check for leaks. Good luck!!

Flooding of the saw when it is standing for a time is generally the needle valve in the carb leaking. This can be caused by hardened diaphragms, worn needle, dirty seat, weak spring or incorrect needle arm height. You can use a pressure gauge or pop off tester on the carb to check it or simply just a short length of fuel line and blow/suck on it to see if it seals. The latter isn't quite as stringent a test but has worked in the past before I got all the relevant kit.

It sounds like he has had the cylinder off already but totally agree with Mr Pleasants synopsis of the big end construction. My method on my 009 included heavy grease and tweezers....not the easiest!!

If it looks like Cherry and smells like Cherry then............

What happened...in the 80s you could get drinks for a night out and a Chinese on the way home for £20.

Sounds like lack of fuel, check the gauze strainer on the pump diaphragm side of the carb. Do take it out to inspect as they can get blocked by a fine scum. If that is OK, try giving the H&L screws 1/2 a turn anticlockwise and that should get the thing running. These saws are usually set on the lean side on manufacturing to save them failing the emissions checks and as the saw gets a bit older, it stops the things revving out.

Yup, his spelling is suspect at best and utter shyte on the other end of the scale. I would never mention such a faux pas🤔👍

Not bad service or price on that, a bummer that they don't do coffee and doughnuts though! Hopefully it is all working and good now.

Ah, the symptoms of excess fuel and not needing choke on cold start like you have are generally contributed to the needle valve not sealing up correctly. This could be a hardened diaphragm, weak needle spring, worn needle or just a poorly adjusted needle arm. A full carb kit may well sort out the issues. Personally I would get one and fit it unless your local arb fixer offers coffee and doughnuts to all customers👍

Looks like Cherry and Plum to me, Apple is smoother and flaky. Agree on the third looking like apple and it does shed bark when older.

I usually turn the L screw in until I hit the high point just before dying and then turn it anticlockwise until I get the idle sounding slightly out of rhythm but 1/8 to 1/4 turn is probably good. The 372XPT can be a bit sensitive to idle speed, I think the ramp up on the coils ignition advance from starting low revs to idle speed wasn't the greatest.

You have pretty much answered your own question. The saw isn't fuelling correctly so you need to inspect the fuel system so we are talking fuel filter, fuel line (not split), the carb (diaphragms and gauze strainer) and the impulse line. The most common issue on an old saw is a split fuel line, clogged gauze strainer or hardened diaphragm. The only caveat to this is that a BIG air leak in the engine can stop fuel vapour being pulled in to the engine but is less likely.

Difficult to tell but your description of the engine not starting until stone cold could be that the engine has low compression and it is dropping off further when warm and making it hard to start. You can measure it with 150psi+ being OK, you can take the exhaust off and inspect the condition of the piston and when there, check the exhaust port isn't clogged with carbon. The cooling down thing can be a dodgy coil or the flywheel to coil gap being too large. You can regap the coil to flywheel with thin paper and this may get a weak spark back up to full tilt. Other than that, the fact the plug is wet may mean the needle valve is leaking letting through too much fuel and flooding the saw but can also mean the engine is just not firing on start up so very difficult to tell. A carb rebuild is my normal start but do check the spark by removing it, earthing the plug on the cylinder and pulling it over to test but make sure the plug is away from the plug hole as you can get some pretty spectacular flames from ignited fuel from the plug hole. In the carb, make sure the needle and spring are sealing correctly, the metering diaphragm is soft and flexible, the pump diaphragm isn't deformed and the flaps are not holed and finally that the gauze strainer isn't full of chip.

I think the coils are limited to 13,200 or thereabouts. My usual method was to tune low and build up revs to the point the tach just went loopy so the carb would be limiting at the same point the coil rev limiter cuts in. Your method may OK if you have the time to do cuts and plug chops to see what you have but I never had the luxury of time so the above gave me what I wanted...a reliable machine doing what it should.

The saw should be set to 13-13.5000 RPM. It may take more but setting tuned saws to near maximum of the manufacturers stated limits is what I always did. Not sure how you are tuning it but taching a saw in this way always ensures the same result.

Yes, all sounds about right. Generally those slider bearings fall apart from lack of grease and implode. There is a C clip that can come off and stop the drive, failure of the "non splined" bearing can stop the drive to the head plus one of those bearings is riveted to the shaft and failure of the rivet can cause lack of drive. Agree that the Stihl diagram is pretty confusing but if you look at it enough with the parts in front of you, it does make sense. The bearings have slots in them to ensure they locate in the large outer shaft correctly....yet another hoop to jump through.

When I was in the game, I appeared to be the only guy in the area that could rebuild these things. It started with one that I took apart in my garage with a mallet and bits shot everywhere so I had to sort out what every bit did and where it went. Once I had done that, it was relatively easy. You are missing one of those funny sliding bearings, you should have two with the splined internals and one with just a round inner. You also appear to be missing the round tube cover that sits on that splined shaft which is a bit baffling as it slides up the round slider bearing you have pictured. These are an acquired taste to rebuild but once you have done a few, it becomes much easier. Oh...you are also missing the fecking great springs that usually sit between the sliding bearings. It has been a while since I last did one.