spudulike

OK, sounds like you are using a compression gauge for a car which will have a much heavier rated schrader valve which isn't a problem for a 1.0 litre engine with electric start but put it on an engine 20 times smaller with a rope and pulley........!! I would still hazard a guess that the main problem won't be an air leak. It may have one but I have only found them ever leaking slightly around the clutch seal, never a major leak. The 372 is a solid machine. If the thing has a spark and sounds like it has compression, the thing to check is the fuel system including the impulse line that has been known to come off. It is always worth doing the pressure and vac test on a wreck as you don't want to get it going only to take out all the work you have put in but don't reckon it will have a big leak unless someone has done something silly. I would be giving the carb a look at, diaphragms are OK, the diaphragm and gasket fitting order is OK, the gauze strainer for blockage, the needle valve for sealing and pressure check this once back together. Check the fuel line (pressure test it), fuel filter and impulse line is OK and connected.

Yup, if you get duff info then you get duff diagnostics. I was working on something going severely wrong with the top end causing the massive drop in compression - a ringless piston would make 75psi. As you said, that 5 mins in your hands usually tells a big story and usually gives you 75% of the story in most cases. The pressure and vac test is the foundation to any good running machine and starts any decent diagnosis on an old machine like this.

I think the Soviet steel thing was never real and it was just down to the Alfa Naples factory being demotivated and pretty much like British Leyland in the mid to late 70s. Not sure about the Fiats - the 2.0L twincam was a beast though! Lancia....Beta...OMG, engines falling out!!!

So the compression reading of 75psi may be 170psi? What is the gauge...make, type etc If you lift the saw up by the starter handle, does it tumble to the ground of hang there on each compression stroke?

With 75psi??....it would need around 130psi bare minimum to fire and run. The 372 bottom ends are pretty solid. The seals tend to be pretty good from past experience. The only thing I ever found was very slight air leaks down that sleeve that goes round the crank on the clutch side or a lightly leaking clutch side seal but never had a major leak. The compression is non existent, unless the gauge is a car one and the compression figure is much higher but hasn't the gauge been tested on another saw??

Show us the damage to the piston. The front looks OK so it is possible the circlip has come out, the end has broken off or the big end is kicking out white metal. Get this diagnosed before putting it back together again.

I thought rot on cars like this was a thing of the past. Having purchased old bangers through the 80s, I was quite used to also purchasing thumping great tins or Upol filler, primer and spray paint. Not seen rust like that since I was looking at purchasing an Alfasud..nice green cloverleaf but it was rusting in weird places...around the filler cap, windscreen wiper holes etc. Didn't bother in the end, great cars but the rust!!!

When you are young, you don't look at the danger or the consequences of doing something a bit stupid and dangerous. When you get a fair bit older, you cling on to what you have in life and know that life is difficult enough with just normal aches and pains let alone ruptured spleen, fractured pelvis, shattered vertebrae, muscle and nerve damege, broken bones etc.....if you are unlucky. Also with age, your balance, strength and general fitness won't be as good as a 20 year old. I will still get up a ladder and don't think too much about it but take less risks than I used to.

The gasket should be between the muffler and heat shield plate and none between the plate and cylinder. I wonder if a circlip has disintegrated between the piston and cylinder fitted or the big end is breaking up. 75psi is almost non existence as 150-175 is more normal on one of these saws. The best option is to clean the OEM cylinder and to fit a new Meteor/Hyway piston. Re-using a seized piston is never a good long term option. The piston skirt does improve compression and does cut down the piston rock at BDC.

Great, lets check out the method of measurement......we have seen so many use a car gauge and register low compression when even a saw with 200psi will register 75psi. If the test shows the saw is at fault, 75psi is VERY low so the top end will need to be removed and the piston/cylinder inspected for damage etc. On heating the plug.....I did that today and bingo, a flooded saw becomes a running saw again!!

I had 5L of brick cleaner left for me by the previous owner of my old house, with a decent amount of HCL in it, it seemed rude not to use it!

The black looks like the residue left when you use acid on the aluminium transfer. The black usually comes off with a bit of rubbing with emery but wouldn't do any more of this unless the black part is a high point.

It looks like piss yellow or I guess you could call it flat cider as well. I wouldn't paint my living room or wear a shirt that colour but guess this isn't what you meant.

Warming the plug is an old school method of starting a reluctant or semi flooded engine. It has the effect of drying a wet plug and also helps vapourise any wet fuel that lands on it when pulling over the engine. Oh....and it works rather well!

This every day of the week. I stick to Volkel taps and use the tapered type as in the pic if the receiving thread is still marginally there. Make sure it goes in dead square and DO NOT buy a cheap kit off Amazon or eBay.....the cheap taps are exactly that, cheap and will destroy your cylinder.

Get a pic of the cutters up Mark, they may be the ones I use for porting and loads of other stuff, purchased a few sets but they last an incredible amount of time and cost bugger all. 4mm dremel shaft I think

I think it is a coil off a 576 but as ADW says, it probably will work. The compression should be 150-170psi when measured with a suitable gauge (not one for cars). I take it this is the old 372 and not the Xtorq, not that it matters much, many Huskys shared similar coils with the same case design but with different ignition advance ramp ups and rev limiter thresholds. Check the piston out, all the gunk may be raising the feel of compression but not actually producing it. A bit of WD40 down the bore, pull it over a few times without the plug in and then spin it over a few times upside down to drain any fluid. Clean the plug, heat it up with a plumbers torch and stick it back in then pull it over on choke WITHOUT using the decomp. If it doesn't fire in 6 pulls, Knock off the choke, hold the throttle open fully and try a few pulls with the throttle wide open and pulling with the other hand. This is frowned upon, it can be dangerous BUT, it can prove an effective way of getting a saw firing if it is proving stubborn. A running engine needs fuel, spark and compression - the spark needs to be at the right time and the fuel needs to be vapourised in the correct manner. Report back with what you find.

Acid or alkali will react with aluminium to form oxide and that helps getting rid of the transferred aluminium. Once the black oxide has formed, you remove the oxide with abrasive paper and add more chemical until it stops fizzing and the plating looks clean. From the wear to the piston, I woulds say that the black patch of oxide is proud of the bore hence the wear occurring. I would stick with the OEM/Meteor option and see if a few hours use will bed it down.

I guess so as the 365 (which I assume you mean) is pretty much the same weight and size but with less go than the 372 so you would only purchase one if you didn't have the £££, you couldn't get a 372 due to stock or you wanted to save a small amount of fuel. All the 365s are relatively easy to mod up to 372 as they share the same bottom end.

I have seen poor filtration cause the Nikasil to wear on the inlet side. It is damn tough but given enough fine wood chip dust through a dirty air filter and it will wear through in time. Funnily enough, the saw in mind was a 024 with a wire mesh air filter.

The black bit just under the left hand side of the port on your second picture looks like it has had chemical on it but the oxide is still present. This mark coincides with the most wear on the piston. The vertical score will lower compression, the high points will wear the piston and ring lowering compression. On this sort of repair, there should be no high bits or deep scores. The scores you may get away with if they are not too deep. All you can do is see how it goes from what you have. The engine will bed down and get better with use sothe best option is to stick some hours on it. If you persist in rubbing small areas of the cylinder, you are likely to cause very small cavities and that really will kill your compression and cause blow by on the ring! 140psi is a bit low on a 024 but it may just be your compression gauge.

I once serviced a blower for a customer. The rats had been chewing his primer bulb so supplied a bit of rat poison with the returned machine. I like to go the extra mile!!

It is an old way of cleaning loose stuff from small tanks. Think of rush on a motorbike fuel tank, that sort of thing....it removes the loose stuff.

I saw a vid on YouTube doing exactly this.