spudulike

Combustion needs fuel, compression and spark. Test the spark by taking it out, placing it in the cap, earthing it on the cylinder away from the plug hole and pulling the saw over fast. Check the plug is wet after trying to start it. If it is wet, chances are you have flooded it. Take he plug out, turn the saw upside down so the plug hole is pointing downward and pull over the saw fast a few times - if flooded, you should get fuel running/spattering out. Dry the plug - a gas hob is good or plumbers lamp, replace the plug and pull it over fast with no choke and the fast idle on but no decomp. If it doesn't fire, try it with the choke on but only 2-3 pulls on full choke! Report back with what you find:thumbup:

The saw body has arrived by the way, just so you know! Yes, spoke to Fred about the lump of wood, tested a ported 372Xtorq on it and left Pauls yard full of sawdust:lol:

They are closing them down Andy, seems we don't need to read now:001_rolleyes:

It may be safer for you if you did, worth doing that and circlips as well, they are the weak points. It does look good, Martin has provisionally booked it in for next Saturday for the lathe work and then......we shall see. It is a learning curve, if the autotune handles this, it will take just about anything! That Beech is bloody massive, around 5' at the largest part, will be attacking it with the old army 181SE as that is really going now I have done the fuel pipe, re-ported it and blanked the regulator off! Time will tell on this one - it has taken quite a while!

Had another go at the 560XP with the carbide burrs over the weekend, anyone reading this - I DON'T KNOW IF IT WILL WORK YET! Until we prove the autotune has enough give in its parameters we don't know what will happen when we hit the wood with it. The muffler has had both the inlet and outlet significantly opened up. The cover over the outlet has now been brazed shut and there really is no need to split the can open to do this. The muffler inlet has been opened to the size of the exhaust port. The uppers have been re-profiled to get the flow to the back of the cylinder, the exhaust port has been widened significantly and the lower edge re-shaped as the straightness was worrying me. The inlet has had little change but have increased inlet duration by porting the piston skirt a little. You can see the damage the stainless stuffer cover did to one of the upper transfers in the first transfer picture. Fortunately, I have managed to smooth it so the piston won't catch and it is away from the compression zone! I have blended the inlet manifold in to the inlet port a little and all that is left is the pop up piston and also working on the cylinder skirt by the transfers.

Very true, caught me out the first time:blushing:

Just to clarify what ADW has correctly said, the saw is a clam type saw and ring clamps are pointless due to the design of the cylinder base. The clamps are usually used on flat bottomed od skirted cylinders and are a way of easing the rings in to the cylinder. On clam cylinders, the ring ends are alligned with the pins as best as possible, the cylinder entrance is oiled and pushed on to the piston until the rings/piston is in the bore. A small bit of rotation of the cylinder may help but you are talking +-10 deg otherwise the ring ends may catch! Go easy and never ram the thing as the rings are brittle and may break!

Probably the clutch needle bearing - get some oil on it and see how it goes. It may also be the crank bearings but a lot less likely!

Interesing thread, my comments - I use "Simply Bearings" to source come bearings and seals, Chain brake - I only snap it on if I am walking with a running saw or repositioning myself on uneven ground with the saw running. I only snap it on at speed to test it during a service and start the saw with it off - I am an engineer so have some respect for the saw:thumbup: On the bearing wear - could this be down to the saws using less fuel oil mix? Less fuel consumption means less oil is covering the saw internals and during heavy use.......... Could the bearing wear be improved with adding a little more oil to the mix? Probably worth trying iMO. I am surprised the flywheel bearing is failing, it is usually the clutch one that gets more abuse from over tightning the chain and extr heat from the clutch. Interesting stuff - perhaps the autotune technology is too good at fuel control and bearing technology has to be looked at to catch up!

Yes but it worries me when you take a saw apart Matty, the hammer is rarely used by most saw technicians:001_rolleyes::lol Seriously, the cardboard method is something I used to use on motorike cylinders and crankcases. It is damn important to get the right length screws in to some holes as an over long bolt can puncture through in to oil tanks or crankcases on some machines!

Thats next on the list, it will be a good work out and judging by the way it pulls, should be good. This was some Walnut Marting dropped off. I know someone that works with wood so was milling it by eye for him - 2' length, no contest, far better than before and sounds glorious when idling, nothing quite like it:thumbup:

Excellent news, salvation at last. Just been out with this ported 181SE of mine, 24" bar, full length, goes like a train and pulls like one, it is bonkers:thumbup:

Procrastination is the thief of time:sneaky2:

Sounds encouraging, 026s are always a bit fussy on the carb, the older ones more so. If you need to hear fourstroking, put the H screw on 1.5 turns out and listen - it will thump and smoke a bit. The L screw on the older carbs does affect the H screw so 3/4 on the L screw may well lean down the H a bit but 3/4 doesn't sound to bad - if you do turn the L screw out, you will need to typically increase the idle speed and one check to ensure it isn't all over the place is to fire it up on the choke off fast idle setting and if it doesn't have a fast idle, you have probably gone out too far! The saw should be close to 1 turn on each, if it is out by a lot, it is showing up a fault!

Keep off the ported page, it is addictive:blushing: Most saws fail due to fuel issues, if the saw idles, the saw is getting enough fuel for it to do that. If the saw revs out when not cutting and then bogs in the cut then it sounds a bit like either lack of fuel or low compression. The 026 generally has a lot of compression, 170psi is very possible and must be over 150psi. Taking off the muffler and looking at the piston for scoring is well worth it - takes 5 minutes and gives you a good indication as to if the saw has seized or not. If the piston/compression looks OK then the issue is probably fuel related. Typical issues will be a holed impulse line, holed fuel line or a blocked carb internal gauze filter. It is also worth making sure that the H screw is 1 turn out from fully in as if it is running lean, this can stop peak power. The 026 is a better saw than the MS181 or Husky 135 etc, these are lightweight home owner saws although some pros use them for lighter cutting and hedge work! If you need a new piston, it is possible that the saw has an airleak and the cost of a decent aftermarket Meteor piston will be circa £25-30 It is also worth checking the wiring where it goes over the top AV mount between the cylinder and rear airbox plate - the wires can chafe and cause a short circuit and therefore a bad spark!

The muffler bolts can be a bit tricky to shift sometimes but once off, you will be able to see the piston and look at its condition. If it is OK, the running issue is probably fuel/carb related!

Yup, that's where my not liking of this device comes from, usually it kills the piston with time. It would be a good reason why the saw is only making 100 psi. You can pull the muffler off to take a look at the piston, any deeper scoring is bad.

If you take the cylinder off, support the von rod well as the big end rollers all fall out if you dont:thumbdown:

Thats a good point ADW has just made, I forgot the 338 had an auto decomp valve - bloody horrible things but he is right that it would drop the compression down. Don't know why you need one on a small saw like this but measuring compression on one of these saws is a PITA as the deomp needs blanking off before testing!

Enjoy fitting that - it is a clam engine so not that easy a job, you will need some liquid gasket for sealing the clam to the upper crankcase/cylinder plus if you remove the oil adjuster, when you screw it back in, push the oiler shaft well in so it doesn't bend the oiler shaft - common error!

I do a similar thing but am not fussed about wood. I have burnt Willow, Poplar, conifer and cedar and as long as it is seasoned, all is good. You are more likely to get this sort of wood FOC!

Possible tank vent, it is also possible that the compression is borderline and when hot, it is too low for combustion so the saw won't start. The coil may be failing when hot, worth checking the flywheel to coil gap as this can do it as well.

You have done a compression test and that is on secondary compression on the cylinder primary being the compression in the crankcase! A pressure test is putting around 10psi presure in to the crankcase and checking for leaks in seals and rubber parts etc sometimes called a leak down test. The 338 needs a new piston unless the ring has snapped, 100psi is very low, the others are OK

I was going to say the same as Stubby is correct. I think Wes is trying to say that the volume of oil going through the saw if the fuel saving is 25% represents the same amount that a mix of oil a 65:1 mix would give but he is American:001_rolleyes: