LumberDutch

The saw was set at just under 1 1/4 turns out on both L and H, so I thought that should be ok. I did not check the revs and maybe it was a bit high (by ear). I have heard of 4-stroking, but am not confident I would always correctly identify it. I mixed fresh fuel and oil and it should have been the right ratio - maybe even a bit more oil (40:1). When hot, I did turn out the L a bit as it was idling too fast. I did not try to turn it in, so an air leak is still possible. So yes, I have been doing some reading on pressure/vac testing and will give that a go. One question: will the pressure at the top of the cylinder (spark plug hole) be the same as in the crank case? I assume with my cylinder in this state that would be the case, maybe it is always the case. It may help me with a diy pressure test setup.....

Hi all - update from me: 1 step forward, 2steps back! Serviced the carb, put new fuel in and ran like a dream. Cut wood for about an hour, started well between cuts. Stalled once but noticed that the fuel tank was just under half-full and with the short fuel line this seems to be a problem. Added fuel and all good again. But then it cut out after another 10 mins, the saw was very hot and did not want to restart! Compression felt bad when pulling, so checked the cylinder and now it is completely scored! I actually now have a compression tester and where previously I had ~130psi (cold) now it is <90. So it looks like I need a new piston & rings (at least), maybe cylinder. But... is there any reason that this would happen. Leaking seals? Checked impulse line and manifold inlet and they are fine. Is there more I should check? Or is this likely due to the initial problem (possible worn/old rings). As always, any suggestions are welcome. I have resigned to this being a "leaning opportunity"

Thanks for the further feedback and the video - very informative! Update: put the saw back together to do the "pushing bar up" test; had to adjust the L screw to get it started and noticed it ran very fast (would go over 13k revs); adjusted H screw down to ~11k rpm (have tach meter) and got it cutting to warm up. In short - the saw now seemed to work ok, no bogging down when hot. One time it stalled, but the fuel level was low (but not completely empty), topped it up and it ran again! Compression seems ok hot, but a slow pull works better than a very fast one for warm start pushing up bar test did not make an difference impulse line looks good, but (maybe) slides into the carb a bit easy... possible airleak? Not sure what is going on here, maybe some dirt still in the carburettor which got flushed out (is that possible?) Still have a carb kit coming and will replace the various filters and diaphragms and see if this makes it run (even) smoother. Again, thank you all for taking the time to share your thoughts and provide suggestions. I may post a (hopefully) final update in a week or so after some more serious use this weekend. And @bmp01no, it was not from FB in Rugby.....

Hi @spudulike, So you think the cylinder may be ok, right? I would be willing to replace it if that would solve the problem. When it runs, I really like the saw. Let me try to answer your questions: compression when cold is good (I'm sure) but will need to double check if it is still ok when hot (bad memory for these things) deep cut when cold: yes, it has excellent power, I was impressed I checked the impulse line and it seemed to be ok, no obvious cracks or holes (I had it out to look at it) I will check the manifold the way you suggest and report back H&L screws are just over 1 turn out I did not check the gauze strainer in detail; will do that; I also have a carb kit coming so will replace the pumping diaphragm and service the carb properly fuel line and filter look ok, but I may replace them anyway; breather is breathing Spark plug is brown/black - this may be an issue; there are also visible exhaust fumes Kill and earth wires are good and not rubbing/bare Thank you again for the excellent feedback and ideas. This turns out to be a bit of a project. I picked it up for next to nothing from a local old boy so don't want to bother him with returning it.

First of all - I want to thank all of you for taking the time to try to help me out here! I really appreciate it and I had no idea there were this many helpful people out there! Second - it turns out not to be easy to get my iphone to properly focus on the piston. Here are a few pics, but I'm not sure they are of good enough quality to tell you much. Please let me know - I can try my other camera.

Hi all - thank you for your quick replies. Cylinder issues was not what I was hoping for, but seems to be a real possibility. I had a look at the cylinder and it does not look badly scored, but I have no real reference.... Some vertical marks, but no real ridges/gaps. Regarding compression, it has a much harder pull than my little Echo saw, so I was hoping that it would be ok. I wondered indeed about the tipping up and down; but maybe I have a multitude of problems (just my luck!)

Hi all - I recently bought a 2nd hand Stihl 026 and initially it seemed to run fine. However, I noticed it started to bog down when hot/cutting at full throttle, and then had trouble starting it again. After cooling down, it starts ok. Also, (and I'm not sure this is related) when I tip the machine up, it revs up, and if the bar points down, its revs reduce.... I read somewhere this could indicate a problem with the intake manifold boot, but since it is not easy to replace this, I hoped someone here might have some advice for me. It has new fuel, sparks ok, I cleaned the airfilter and cleaned the small filter in the carburettor (which was initially dirty).... Any advice would be welcome!