bmp01

Worth noting, in theory it is possible for the engine to suck loose debris from the exhaust back into the cylinder, although even less likely if it's t'side of a catalyst. Use an air line or what every you have to blow out swarf or grinding dust from exhaust. Better safe than sorry.

It's a one way trip isn't it ? Do what ever is easiest with the tools you have. Drill and dremel work for me when opening exhaust outlets, removing dividers or spark screens etc. Pair of pliers and a small hook to remove thick wire ball from a chinese top handle exhaust, that wasnt catalyst wire but it wanted gone all the same.

Had this bit left over after playing with early MS201T 😄

That's a nice bit of workmanship ! Somewhat louder ??

Weird, that's never happened before.

Yep. Accelerator pump circuit is a good thing as new - nice throttle response. Sadly it doesnt stay that way forever and has a lot to answer for in terms of irregular or intermitant poor running. At the end of the day its a bit of unnecessary baggage to help with emissions legislations. But just deleting it doesnt always work because the rest of the carb is setup to work along side a functioning accelerator pump. Accelerator pumps didnt always exist though; it is possible to get decent throttle response with out one. As Spud says best make sure nothing else is wrong with saw before going down this rabbit hole.

14.5 psi to 1 bar 1000 psi = 69 bar in the ball park, maybe a little high.

Old tech by now, cylinder pressure measurement in high speed 4 stroke engines was done with piezo electric pressure transducers couple of decades ago. Getting a real pressure trace was possible, relating pressure trace to crank angle less convincing. Ball park peak pressures 100 -110 bar at max torque, engines had static compresion ratio 11, 12, 13, that sort of thing. I'd punt at 50-60% of that for decent brand 2 stroke engine, maybe 75% for a tuned 2 stroke engine.

Sounds like blocked exhaust to me (adw there first). But not high use .... exhaust blocked with some creatures nest or something ? Edit : could be insufficient air going in if its going rich (smoking) with open throttle but filters ok so blocked air inlet, ie before the filter.

Oil spec on current car engines is all about fuel economy and emissions reduction (so thin oils for lower viscous drag) - not necessarily whats best for engine longevity. But then again modern engines are generaly good enough to last the warantee period and then some so theres some flexibility there.

I've edited your pictures with red circle to show where the impulse signal is going through to the carb. So the impulse line needs to connect to engine side of the orange plastic, which is what Chris stated 2 posts back....

As per adw's question a few posts above how does the impulse signal connect to the carb on the MS261 ? You need an impulse pressure signal to make the pump side of the carb work. The pressure pulses causes the membrane to move in and out ---> fuel is pumped through the one way flapper valves. Worth noting: -Engine will run on choke without the impulse pressure signal because the closed choke causes sufficient vacuum to suck fuel directly from tank. -Engine will often run at wide open throttle without the impulse signal because the high engine speed often causes sufficuent vacuum in the carb ventui to suck fuel directly from tank. -Most other scenarios, no impulse pressure signal usually means engine wont run.

I think the blue ones, which are fairly recent, are already assembled ? Each 'new' model they bring out is supposely better than the previous, but old models were pretty dire so might not be saying much. I've not touched one so that's now third hand reporting 😃

If you get to parking it I'd be interested in buying it, I'd like to see the 'naff' quality of a 'Farmertec' kit saw for myself. Reasonably confident it will run by the time I've finished with it, might even run quite well. PM me if this of interest.

Going back to why saw won't fire even when you've added fuel; Have you swapped in a good spark plug ? Have you tried getting the ignition system to jump a big plug gap ? It's sometimes the case the ignition appears to work with the standard plug out of the engine but once plug is under pressure in the cylinder it falls over. WRT timing - what matters is piston position when flywheel is passing the coil. There will be variations in coil design and in the advance curves within the electronics of the coil but you'll get some idea if things are about right if you compare this one with your 260. Good luck.

Well this is a fun thread. There's only one rule - you have to let us know when you get it running and report on your findings.

Personally I've never seen any trouble with bearings from running wrong oil/petrol mix. Plenty of piston problems of course but even those saws that seize pistons, more often than not bearings are ok after a good clean. First thing to go with wrong oil mix is the piston - be interesting with this one to pull the exhaust off and take a look at piston skirt and piston rings.

That last bit might undo your plan....not sure a 6T rim sprocket exists. Dont forget the outside diameter of the rim sprocket is proportional to number of teeth - that's to say a 6 T rim might be too small to function on the splined clutch drum. Happy to be proved wrong.....

Thanks for the tips. I can feel some repair work coming on. I've got a busted pole saw head in need of fixing too.

I agree with Ramsey's experience, toolless tensioner is simply inadequate, I've dug into it in the past to look for a solution .... failed. The standard single bolt / nut is just fine though. Good news is you can sell the secondhand toolless tensioner parts on ebay 😃

Cranks not rotating though when youre pulling the chain round by hand. Points to eccentricity in the clutch housing or rim sprocket. Or the interface between the two - the rim sprocket is a loose fit on the clutch so it will 'walk' around on the drive teeth as the chain is pulled round by hand (probably locks up in one position when the engine is turning it over at speed).

Clamping the chain like this (on the side faces of the drive link) that ought to stop the chain from rocking in the direction you file it (I mean across the guide bar). It annoys me how much the chain wriggles about when filing, especially on the fiddly chains or worn bars. I like the idea for loose chains but not sure how many times I'd pull a chain off assembled saw to use the cIamp set up.

Blimey, this thread has taken a weird turn along the way.... We're good. You know the way it is, stuff that makes sense in yer head doesn't always make it onto the page in the most comprehensible fashioned. Out of respect for yourself and other readers thought it best to make it clearer...ish. Wonder if OP has fixed his saw ? Probably wondering what the heck he has wandered into.....

Just incase we're not all on the same page. .... The purge bulb pulls fuel into the carb only. You'll not see fuel in the engine until you pull the engine over. So whats next... If you can see fuel returning to tank as you press the purge bulb then you have fuel in the carb and in the right place, ie the metering side of the carb (assuming pipes are correct).Turning engine over with the choke on at this stage will then get fuel into the cylinder. Most likely too much fuel even if there is an air Ieak. Impulse line wont have much effect at this stage, thats only useful after engine is up and running. If the plug gets properly wet you’ve flooded it, dry the plug, pull engine over with plug out etc. I'd go for 1/2 a teaspoon of fuel down the plug hole, plug back in, choke off and see if it will cough. Repeat. If it coughs or runs at all, its 99% certain a fuelling issue. Amendment to my post up the page, shown in Italics, play spot the difference adw - ok now?

Just incase we're not all on the same page. .... The purge bulb pulls fuel into the carb and no further. You'll not see fuel in the engine until you pull the engine over. But if you can see fuel returning to tank as you press the purge bulb then you have fuel in the carb and in the right place, ie the metering side of the carb (assuming pipes are correct). Turning engine over with the choke on will get fuel into the cylinder, most likely too much fuel even if there is an air Ieak. Impulse line wont have much effect at this stage, thats only after its up and running. If the plug gets properly wet youve flooded it, dry the plug, pull engine over with plug still out etc. I'd go for 1/2 a teaspoon of fuel down the plug hole, plug back in, choke off and see if it will cough. Repeat. If it coughs or runs at all, its 99% certain a fuelling issue.