Spring
ArboristSite Lurker
Ok, nothing new here. I had a request to post the process that I used on my Stihl 250. In fact, some of the past threads are much more detailed about chainsaw modding, but this is a step by step by picture for those wanted to follow along. I owe much gratitude to the awesome people on this forum.
1) Muffler removal
Muffler removal.JPG (165.8 KB)
This just shows how to remove the muffler. Loosen the two nuts and pull the muffler right off the long bolts. Easy.
2) Muffler modification
Muffler in parts.jpg (62.2 KB)
The Muffler can be broken down by removing the front baffle and screen, leaving the muffler. The muffler image shows how I enlarged the hole that was original. I just took a 1/2 drill bit and used it to enlarge the hole so that it was the entire area was opened. I finished it off with a dremel tool to give it clean edges.
I didn't need to adjust the other side, assuming the front hole was what really needed to be enlarged.
BE SURE TO GET ALL THE METAL FILINGS OUT OF THE MUFFLER. If you don't they can blow back into the cylinder causing serious trouble.
Once you have done the modification for the muffler itself, attach it back on. Some people remove the screen all together, but I don't want stuff getting inside the muffler/cyl, so I re-installed it.
3) Carb Access
GettingToCarb.jpg (82.7 KB)
Carb.jpg (69.5 KB)
Remove the filter and the filter attachment by removing the two nuts. The carb can move on the bolts, so pull it out slightly to help access the rubber boot that is around the screw you need to access.
4) Adjusting limiting cap
LimitingCaponHigh.JPG (145.8 KB)
The rubber boot is pulled away from the set of three screws, the one you need to work on is the one closest to you, as the pencil indicates. The High screw you are adjusting will keep the saw from running too lean, meaning not enough fuel based on the air it is bringing in(I think that is a decent explanation) Because the muffler brings more air...you need more fuel, right?
The EPA / Stihl try to prevent you from making the adjustment by fitting a plastic tube around the High screw. That plastic tube has a rise on it, preventing turning the screw. You can see the rise hits the metal post that is next to the High screw.
I have read on this site all the ways to remove the limiting tab..but I just shaved it down with a razor blade. It is easy and just needs to be shaved a little so it doesn't prevent the High from turning out more.
Once the shaved limiting screw is completed, pull the carb out on the bolts and re-install the rubber boot. Assemble the saw back to orginial.
The saw is almost complete. All you have to do is adjust the the High Screw so it runs properly. The best way to adjust the screw is turn it all way so you seat the screw( not too hard though!!!). Then, back it out at least 3/4 of a turn and start the saw up. The fine tuning is sorta complicated, but this is what you are going for...keep turning the screw to open it up even more until at full throttle the saw is making a deep gurggling noise as it is at max throttle. Then, seat the screw back to thin that gurggle out and get higher rpms. Its a fine balance, but you will hear the difference as you turn the screw back and forth. If you gurggle it too much, you will waste gas and it will not cut at the high rpms. If you make it too lean (high pitched scream as it runs) you will lose all the cutting power and ruin your saw.
Check out "chainsaw tuning" threads or even on google to get a better idea if you don't feel comfortable with the adjustment. I leave mine slightly rich with fuel because I don't want my Stihl running too hot and lean.
Let me know if this helps Rusty! BTW...it was completely worth it. My saw runs much better! I tore up some oak with the 250 about a month ago...and stock it probably would have been a more frustrating experience. Im amazed at the difference!
1) Muffler removal
Muffler removal.JPG (165.8 KB)
This just shows how to remove the muffler. Loosen the two nuts and pull the muffler right off the long bolts. Easy.
2) Muffler modification
Muffler in parts.jpg (62.2 KB)
The Muffler can be broken down by removing the front baffle and screen, leaving the muffler. The muffler image shows how I enlarged the hole that was original. I just took a 1/2 drill bit and used it to enlarge the hole so that it was the entire area was opened. I finished it off with a dremel tool to give it clean edges.
I didn't need to adjust the other side, assuming the front hole was what really needed to be enlarged.
BE SURE TO GET ALL THE METAL FILINGS OUT OF THE MUFFLER. If you don't they can blow back into the cylinder causing serious trouble.
Once you have done the modification for the muffler itself, attach it back on. Some people remove the screen all together, but I don't want stuff getting inside the muffler/cyl, so I re-installed it.
3) Carb Access
GettingToCarb.jpg (82.7 KB)
Carb.jpg (69.5 KB)
Remove the filter and the filter attachment by removing the two nuts. The carb can move on the bolts, so pull it out slightly to help access the rubber boot that is around the screw you need to access.
4) Adjusting limiting cap
LimitingCaponHigh.JPG (145.8 KB)
The rubber boot is pulled away from the set of three screws, the one you need to work on is the one closest to you, as the pencil indicates. The High screw you are adjusting will keep the saw from running too lean, meaning not enough fuel based on the air it is bringing in(I think that is a decent explanation) Because the muffler brings more air...you need more fuel, right?
The EPA / Stihl try to prevent you from making the adjustment by fitting a plastic tube around the High screw. That plastic tube has a rise on it, preventing turning the screw. You can see the rise hits the metal post that is next to the High screw.
I have read on this site all the ways to remove the limiting tab..but I just shaved it down with a razor blade. It is easy and just needs to be shaved a little so it doesn't prevent the High from turning out more.
Once the shaved limiting screw is completed, pull the carb out on the bolts and re-install the rubber boot. Assemble the saw back to orginial.
The saw is almost complete. All you have to do is adjust the the High Screw so it runs properly. The best way to adjust the screw is turn it all way so you seat the screw( not too hard though!!!). Then, back it out at least 3/4 of a turn and start the saw up. The fine tuning is sorta complicated, but this is what you are going for...keep turning the screw to open it up even more until at full throttle the saw is making a deep gurggling noise as it is at max throttle. Then, seat the screw back to thin that gurggle out and get higher rpms. Its a fine balance, but you will hear the difference as you turn the screw back and forth. If you gurggle it too much, you will waste gas and it will not cut at the high rpms. If you make it too lean (high pitched scream as it runs) you will lose all the cutting power and ruin your saw.
Check out "chainsaw tuning" threads or even on google to get a better idea if you don't feel comfortable with the adjustment. I leave mine slightly rich with fuel because I don't want my Stihl running too hot and lean.
Let me know if this helps Rusty! BTW...it was completely worth it. My saw runs much better! I tore up some oak with the 250 about a month ago...and stock it probably would have been a more frustrating experience. Im amazed at the difference!
