bmp01

As per previous comments, if you don't fix the route cause its going to happen again. It would seem you never quite got the saw fixed in the first round of repairs so you'll be looking to dig a bit deeper this time. Air leak is favourite, so make sure you pressure test the repaired saw or get someone to do it. Only useful thing to add, if the original cylinder isn't trashed too bad it can probably be brought back to life by removing the aluminium deposits. Takes time but if you end up with a good, genuine used cylinder I'd take that over a replacement one. ... do a bit of research on here for 'how to....' It's a good saw, worth the effort.

Going through a rather tired MS171 which came to me as a box of bits, nothing very exciting. Reason for posting - noisy crank bearing led me to remove and disassemble the bearing, idle curiosity. Picture is worth a look. Look at the ball sat on the blutak - the outer layer has disintegrated. Poor quality steel I imagine. Bearing is Chinese, with C4 clearance, i thought these were C3 clearance so might be an aftermarket item ? bmp01

Jeez, that's some oil slick Yeah, I can sort of see the problem, exit in the exhaust is quite high up, higher than the exhaust port. And there's a stupidly small internal passageway inside the exhaust that would stop the oil draining even when you tip the saw forward. Ho-hum. Easy in hind sight innit... So, how big was that mysterious blue cloud over Heanor today then ?

Nice one Micky, good result. As to your question, took the plug out and span it over with a drill ......

Did you get much oil out of it? Put the clutch drum back on (if you haven't already) before firing it up.

Piston's Peachy. No problems there. Strange exhaust port though, bit difficult to make out the shape, not seen one like that before. .... Is it a genuine cylinder I wonder ? bmp01

Ok, thanks for clarification. ... seems i misunderstood, got the wrong end of the stick, etc, etc. As others pointed out, if it turns easily with the plug out, there is no need to be looking at clutches, chain brake, ignition coil foulIng the flywheel - my mistake, apologies. Still worth posting a picture of the piston seen through the exhaust, or at least confirm the piston is good. You should see the faint machining lines running around the bottom half of the piston, so below the piston ring. Any vertical lines are damage. There's a thread here just recently "Does this cylinder need replacing" with some good pictures in it. So have you managed to get any gunk (oil) out of the saw ? Keep us posted. I'm close to Jn 16 on the M1, bit of a trek but happy to help ... bmp01

And 3 pounds of that was for the accelerator pump parts

If that's above the exhaust port, yeah not much choice. Below the exhaust port. .... you might get away with it. What piston are you going to fit ? That will tell us how much you value the rebuild bmp01

On the up side there's learning to be done. An appreciation of how a saw works and is put together is no bad thing. Might even help with using the saw once its fixed.

Micky, Ok. So what was the reasoning for the oil back then?

Yeah, best to have some knowledge so you can filter the offerings. Or learn quick !

I can see the logic in that. Should be the simple start mech but even so could be something that binds when it's under load and doesn't when the plug is out (no load).

Ok. So, what was the reasoning with putting oil in there in the first place?

Just a thought on the hydraulic lock theory suggested here with loil below the piston - if the saw is held completely upside down, the piston will be like a cup holding on to the oil. To get that fluid out, place the saw on its side (either the chain side or the pull start side) and turn the engine over, this should allow the liquid to flow through the transfer ports to the top of the piston. Then you can turn it upside down again and drain from the spark plug or if the exhaust is still off you can drain it from there....

Good result, another one dragged back from the grave ! I have to say that's brilliant service, running saw AND a detailed diagnosis report. Don't see that too often. Did i mention I hate accelerator pumps before now . .... I did ?..... Oh ok, I'll shut up then. ....

It could. ...... but then again it might never, ever ...... run again..... I get the feeling is either goosed or something daft. And before long it will be more economic to just swap the engine (and carb) for some aftermarket parts.

If you read the first post through he says it was hard pull over and that's why he put some thin oil down the plug hole. .... it subsequently loosened up (or he just got used to pulling it over). Maybe the O.P. can confirm that's true AND if the brake was on or off and if the ignition module had been gapped correctly at that stage. Actually just take the 5odding ignition module off, take the clutch off, and show us a picture of the piston through the exhaust port....... bmp01

Micky, It probably would be quicker/easier to get some one to look at it for you. But before you do a couple of quick things to put to bed: -Post a picture of the piston as seen through the exhaust port (now you've got exhaust off). -Really make sure you've got the chain brake disengaged. -Pull the clutch drum off ( its the thing the drive sprocket is joined to, held on with the 'E' clip) and the bearing inside. You need the chain brake disengaged to do this as the brake band will grip the outside of the clutch drum. Do NOT attempt start the saw like this (ignition off please while you pull the cord) we're just trying to find out if the clutch was making the saw hard to turn over. Maybe there will be a clue in here. By the way, not every MS181 has the Stihl easy start mech, but it's a small displacement saw that should pull over pretty easy anyway. bmp01

The thing is the oil filter is more of a rock catcher than a filter. And the stupid flippy cap filler hole - is designed to catch (and trap) saw chips - its pretty difficult to imagine any oil pump having a long happy life. At least on the 170 / 180 you have an oil cap that covers the filler hole.....

Cor blimey, where to start...... What were storage conditions? Warm and dry or cold and damp etc? 1) Saw should not be hard to pull over just because it's been stored. 2) Coil should not go bad just because it's been stored. Have you got any evidence of corrosion on the outside of the engine, rusty steel parts, dusty white deposits on aluminium? Has the clutch rusted up, or is the chain brake on? Can you pull the chain round easily by hand? The oil you put in the cylinder will be causing a really good seal around the piston whereas the (dry) piston ring would allow some gas past. In addition, if there is enough oil in there, you will also increase the compression ratio. That is why it is hard to pull over. I would add some petrol to the brew, pull it over with out the plug in - then turn the whole saw upside down and pull it over. The intention being to empty out all the oil. IF you get it to a state where it pulls over sensibly with the plug in, then you can move on. A squirt of fresh 2 stroke mix down the plug hole, see if it coughs. ....

Yep, that skinny chain cuts a narrow kerf, makes the most of the 170's power - but really fragile. Every thing is fine in clean wood but hit a stone and the teeth fall off. 180 has a few more cc's and little more power. Carbs have idle speed adjustment only. Not had any trouble with oil pumps personally, but known to be weak, block up and wear out at high miles. It is the same pump as the Stihl pole saw. bmp01

If I'm reading that correctly a modified exhaust isn't what you need, or at least not straight away. The first thing your saw needs is some maintenance and a tune up. Either that or the 2 stroke your using isn't fit for purpose, could be an old fuel/oil mix ?? What you've described sounds like your saw is running rich - too much fuel in the air / fuel mixture. Is your saw chucking out blue smoke? Engine maintenance, clean the air filter, new spark plug, general clean and check the carb doesn't have the choke suck on.... Carb tuning has potential to 8ugger your saw if not done correctly, do a search for correct procedure. Exhaust mods, can be as crude as just making bigger holes, drill, files, Dremel. .. that sort of thing. ATB, bmp01

There are always exception to the rule but generally speaking exhausts are not interchangeable. There are plenty of modified exhausts aimed at improving engine performance but mainly these are the original exhaust which is then modified by tuners (or diyer's). 99% of the time the aim is simply to reduce the back pressure on the engine - think bigger exit hole(s). The 1% of the time a tuned pipe is used to create pressure waves to help pack as much fuel and air into the combustion chamber as the exhaust port closes (trouble is the required pipe length is too big to package sensibly for every day use). The benefit of a modified exhaust (or muffler mod in US speak) is dependant on how strangled the exhaust is in the first place and another general rule - older saws were less strangled than modern emission regulated saws. The recent tend has been to make an exhaust with a small exit hole and convoluted path for the gases to travel through - with the intention of reducing the amount of air and unburnt fuel being spilted out the exhaust (during the scavenge stage of the 2 stroke cycle). The attached picture is an exhaust for Stihl MS211 / 181 /171. Original exhaust has an internal passageway plus small exit. The modified one has 2 outlets, my intention was primarily more passageway area. The internal baffling was also removed. Back to back testing confirmed a big performance gain. After the basic stuff like saw maintenance, in particular a sharp chain, the biggest performance gain is usually through exhaust mods. Please note: the carburetor must be retuned to ensure correct fueling after exhaust tuning - otherwise you are likely to seize the engine.

Forest, Was that second new chain similarly affected ? Your dealer ought to hear about this and if he's got any lead in his pencil he ought to get onto Oregon swiftish. I'm not going to say too much but the implications of running that setup are not good - we have a responsibility to do something about it. bmp01