bmp01

It's actually pretty good isn't it. If you have the time and a carb on the bench it will teach you how the carb is supposed to work but watch out for a few variations on the general theme. Can't remember, does it have the good old acceleration jet circuit in there too?

Not looked into it in any great depth, but similar to you I had been using a Stihl depth gauge and moved on to Oregon (new chain maintenance kit) and noticed the Oregon depth gauge was suggesting I file more off of the rakers. ... I didn't follow it up to find out which was in error. Might be worth a measure of a new chain, although i guess there is no guarantee that is correct.

Emissions are worse, assuming all other running conditions are the same. ... Fundamentally, the manufacturers were forced by legislation to improve on emissions - so the first thing they did was to make the exit hole in the exhaust smaller. That works by increasing the back pressure on the engine, forcing some of the unburnt fuel and air back into the engine, reduced emissions but also reduced performance. So guess what the first step of tuning is ?? Ok, so thats a very general comment and primarily applies to older generation (pre strato saws) but it is still true to a lesser extent on more modern saws. Other aspects of tuning that improve combustion can reduce emissions - as simple as tuning the carb properly or more complicated an increase in compression ratio, spark advance. Porting changes including port timing - in general will increase gas flow through the engine, most likely to increase emissions .... I'd wager any one interested in getting more from a saw is also likely to maintain it and keep it running properly which in itself will reduce emissions. ...

Link to Rob's You Tube on this. (If it works ! ? !) https://www.google.co.uk/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3DV7P-jyBgu_Q&ved=0ahUKEwirsuiGlqDYAhXPFsAKHTzTBUoQwqsBCE4wBg&usg=AOvVaw3g5KyRz7d8iLIut2wDCuip

Trouble is lots of stuff gets sold when there are problems. Sure there are a few genuine "got no use for it" or "need the money" type sales but there are very few real bargains because the value is so easy to establish with the Internet. Plenty of stolen goods too i guess but i digress. Caution is the order of the day which you clearly know. Personally I'm never happy with a used saw until I've found (and fixed) a few problems, in the hope that was why it was up for sale. .... Twisted logic

Nope..... not a chance. .....

Yes, well, that's the same the world over. But my point: 181 is basically a 171 with a tiny bit bigger piston (same stroke). If a clapped out 171 out cuts a 170 then a 181 will too. The 211 is the one to have though in this class of saw, biggest engine in the same saw frame.

Something not right with the 181 then. A bit of a coincidence - i was checking a rebuilt 171 today. Needed a bar and chain so i borrowed the one off my 170, and took the chance to compare the two saws. The 171 has a misfire at peek rpm, coil i think, but it was still quicker in the cut than the 170. Wood varied in sized but upto 10 ", same bar and chain. A 181 should be a step forward.

Ok, that's it then, sorted. Quicker and easier to do - than to explain it ..... again.

Pretty straight forward..... takes me back to the days of setting the timing by rotating the distributor back and forth. .. remember them ??? Back to the present, that strobe test would be worth while. But you need to know what the spark advance should be in the first place before you can draw any conclusion.

Yeah you're right, my comment was incorrect, my intention was to keep away from max rpm while checking the coil (to avoid any misleading behaviour) which is still the right approach I think. Worth noting: In and out of 4 stroking due to fuel mixture does cause engine speed to oscillate somewhat but with an electronic tach which averages several revolutions you get a sensible speed reading. Compare that with an rpm limited coil dishing out spark cuts, counting sparks with electronic tach to determine rpm just don't work. (Ironically though, the engine speed is precisely controlled by the electronics at that stage and the mechanical bits are seeing a constant rpm ). Spud - any idea if the 024 coil has an advance curve in it or fixed timing?

Sorry to hear some bu88er has messed up your happy setup. Regarding the 181 its not a high torque saw, generally needs to be kept spinning fast and not loaded up - so don't push on it. The wider chain is what it is - you will be removing more wood with each cut compared to the micro chain and need more torque to do so. I've always been pleasantly surprised how well those thin chains cut but the down side is they are very fragile. Even though you are used to the low power 170, try the 181 with attention to a light cut aiming to keep the speed up. And keep a good eye on a sharp chain. Give it 3 or 4 tanks worth to loosen up.

You might get some weird numbers at max rpm even without a limiting coil - if the saw is 4 stroking the real rpm will be all over the place anyway. But upto 10000 (let's say) rpm should be pretty stable. With the age of saw it's quite possible the spark plug lead is past its best too. Expect you can you change the lead by itself on this coil. Thing is, from your video sound track it didn't sound like there were misfires during the cut, just low power.... What about spark advance - i don't know if these coils have an advance curve built in or fixed timing but a retarded spark would considerably reduce power. Same would happen if the flywheel has lost its timing or been messed with.

They don't sound hugely different in terms of how they react to load.... play back through any computer isn't going to be ideal and can't tell what load you are applying. But here's what i thought. -Neither saw seemed very responsive, they don't rev up crispy. -Sounded to me like the second saw (251) was a bit low on revs and quite a heavy 4 stroking out of the cut. (I know you're not questioning this one, but to me that's not where it should be). -Yes, the 240 is a lower engine speed still and struggling. Have you considered bar and chain differences, is it worth a chain and bar swap between the two? How you have set the raker heights on the chain(s)? Its as if the rakers are too low. But then if the engine is gutless i guess its going to behave like that. Probably a red herring but worth an ask. Did you get the compression test done? Unlikely to be any silver bullets here, going by Spuds opinion but it don't do any harm to consider a few alternatives Also, didn't you say the saws behaviour was essentially the same when it was on Stihl pot and piston ?

So, how it works. .. Under choke conditions the choke blocks the inlet track (duh !) which causes a big depression in the carb port AND in the metering chamber (via the tiny jet holes). It's a much stronger depression with choke compared to normal running condition. It's the depression that sucks the metering gasket down onto the metering arm thereby opening the metering valve. Quite simply the bigger the depression the further the valve opens. If you are marginal on opening the metering valve you can see the height of the metering arm or the size of the 'pip' on the gasket are important. If the metering gasket is up side down. ... there's no 'pip' on gasket, so need big depression to get any movement of the meterIng arm and valve. HTH.

+1 Having the metering chamber gasket the wrong way up does exactly what you experienced. ...runs on choke, runs on fast idle then dies, repeat as often you like. Don't ask me how i know this. If the metering arm height is set too low it could do exactly the same. Just saying .......

That's a whole lot of ally swarf and big chunks to collect on the piston must happened pretty quick, a few seconds only, maybe as saw slowed down. It's piston crown is cracked through. ...? I'm not sure if i can see a cracked piston there or not. Would that be primary or secondary failure? Crankcase is brown, piston is same colour above and below the ring so I'd guess combustion gases below the piston. Edit: but the ring is stuck so that might be a red herring. .. Don't know what that other 'stuff' is on the piston, looks like chewed up green plastic, bearing cage? Is there any ally below the piston - can't see any, but blurry though. Good puzzle, another clue please....

Thanks for replies, balanced opinions based on usage I'm guessing. Right then, had a chance to give the saw a once over. It's actually 2002 model, nearly complete, missing an AV mount under the exhaust. 25" Bar and chain, chain has had it, needs a new rim sproket too, otherwise and cosmetically pretty good. Unfortunately, the compression tester says, 135 psi (125 to start, with decomp button in). What i can see of the cylinder through the spark plug hole (exhaust side) looks nice and shiny. The plug was well carboned up. Running at idle, it rattles just a little bit, not imminent death but just enough to make you wonder. Is this typical? Blips nice and revs out fine. I guess if it's a genuine healthy cylinder and needs either a set of rings or a piston that's ok - are there any external casting marks to identify the cylinder? Thanks, bmp01

Jeez, really ? We better not think about the cost to get to a dealer to collect Aspen then ....... or the time wasted waited for a delivery. Don't get me wrong, i think Aspen is a good product but it needs to be sold on its merits.

Spud, Thanks for that, rather encouraging. Fingers crossed then. I'll check the compression and pop the exhaust off - just to be sure.

Hello, I'm out of my depth here - are there any model specific weak points on a Husky 395XP, 2004 vintage ? I'm told the saw runs fine, idles ok has decent compression etc pictures show the plastics are decent. Are there any weaknesses in the chain drive, oil pumps, chain brake ? Or anything else critical / expensive that wears or fails? Thank you.

Was the cylinder and piston assy a genuine part - the one that failed? Not often you see that. .... After market circlips and rings on the other hand are less reliable, some builders substitute these parts with genuine ones. Personally i don't like circlips with those extra "grab here" features on them - the extra wire mass is subject to the same accelerations as the rest on the piston and that means there more likely to move / fret / break.

No fuel through the low speed circuit in the carb? Has the 'new' carb been proven work properly? Do you manage to the saw start with the choke enabled? Will it then run briefly at low speed or not at all ? bmp01

I would be tempted to pressure test the saw before you pull it apart, nothing to lose and maybe learn something useful.

All aftermarket pistons are cheap really, even decent Meteor brand. Time and effort to clean up a genuine cylinder etc, 10 pound cheapie or a 25 pound Meteor piston....... I don't feel the need to experiment with cheap