I have a Stihl MS250. Originally, it was the easy start, quick adjust model. I have changed the quick adjust chain tension system to the standard system with the studs and nuts and changed the outer chain cover. However, I seem to be always adjusting the chain on this saw. It is almost as if I can tighten it down to the proper tension and as soon as the chain and bar see a piece of wood, the chain is slack again. I understand that a chain will need tightening with continued use, but this one seems to be constantly loose.
It currently has a 16" bar on it that I got with the saw when I bought it used. I have been wanting to move up to a 18" bar, but that will be that much more chain that will be loose. I know the saw needs a new chain sprocket, the current one is badly worn and I will be ordering a new on this week. Could that be part of the issue with chain tension? Could installing a new bar and chain help to solve the problem?
It is a great saw, when it is not flooding out and hard to crank (I think I have figured out why and will fix this) so I want to correct the chain tension issue and keep running it.
Thanks
The badly worn sprocket is the clue. The chain will try to ride up in the groove causing it to tension, as soon as it drops back in the groove it is too loose.
Welcome to the Forestry Forum, knightgang. 8)
New drive sprocket drum or rim and don't forget the other chain sprocket on the other end of the bar.
Start all over with new chain included.
Are you lifting the nose of the bar while you tension, up until you tighten the bar nuts?
New chain, new sprocket, and check the bar wear for starters.
Here's how I tighten the chain/bar. Take the chain-brake off, loosen nuts up some, and adjust the chain tension screw to desired tightness. Next, I place the outermost tip of the bar on something while holding the rear handle. All the weight is on the bar pushing the tip upwards. Re-check the droop of the chain in relation to the bar. It should have much more of a gap. Re-tighten the chain adjustment screw a hair. Now I tighten the front nut tight. This should cause the chain to rise up closer to the bottom rails on the bar. I run mine with the droop about the thickness of a nickel. Tighten the rear nut completely. By hand (with gloves on), rotate the chain around the bar a few times. It should stay at the proper tension.
A new chain will heat up and stretch or elongate during the first tank of gas, so you'll need to keep an eye on the tension. When it gets slack, readjust as described.
Hope this helps.
Another way to tension your chain is loosen the bar nuts and lay the saw on the ground upside down. The bar automatically falls in the right position. ....adjust tension screw, spin chain for a rotation then tighten front nut first , rear nut last.