Little late but I own this exact saw as well. I have cut down over 50 trees with it, Some of them so large I had to cut from two sides to get all the way through the tree; Buried the bar. In terms of the engine, the power, and the reliability, the saw is fantastic for its size and price point. The only times Ive felt it struggle with power is in these huge trees where I have burried the full 18 inch bar, and even then It still managed to power through.
I do have a few things that have annoyed me with the saw though, and it is all with the chain tension system. I have only owned a handfull of chainsaws. I tend to buy one and use it until its wore slap out. My last chainsaw prior to this one was a husqvarna, which was the traditional tension system that required tools. I feel like on the Stihl 251, I often end up hitting the limit of tension space from chains stretching, faster. I have about 6 chains now hanging on a nail in my shop that are perfectly sharp, and not terribly old chains, but they strethed enough that I cant get them tight on the 251 any longer, without removing a link. I just never had this problem nearly as bad on the old husqvarna. I feel like it was able to push the bar further and keep tension much longer on chains. Chain stretching is a known issue though with chainsaws, and given I dont have a ton of saw ownership experience it could mean that this is a very common problem, I just know it never has been an issue until I got the MS 251 CB-E. I can put a new chain on it, and if I work the saw heavy for just like 2 weekends in a row the chain tension is already running out of room on the 251. I have taken steps to try and minimize chain stretching by going easy on brand new chains, warming them up with plenty of oil first, by not over tightening them, etc etc, but nothing makes an impactful difference. It just feels to me the 251 cb-e doesnt have enough tensioning space to work with.
I love the engine and feel of the stihl over my previous husqvarna. I do think that my next saw however will NOT be another tool-less design. Because ofthe above issue, and because it just feels that Im always dealing with a chain that feels looser more often. For example - I have thrown the chain way more often on this MS 251 than I ever did on the husqvarna. Its hard to say if the tensioner is losing just a tad of tightness after setting it, or what, but Ive just never been 100% satisfied personally with the chain tension mechanism as a whole on this saw. While I have never broken it, I also do always worry that the plastic tension spindle handle is going to break one day.
