That dosen`t sound to bad. You may had luck and everything is fine.
MS 193t mods
- Thread starter FredBear
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FredBear
ArboristSite Lurker
thanks for your help. I really appreciate it
Your welcome, no problem.
FredBear
ArboristSite Lurker
Piston looked fine. With the H screw 2 turns out and the L screw 1 turn out, the saw sounds boggy in the cut.
Please read the tuning description again (the last step). With the H=2 you get around 12.000rpm and then you have to remove the tach because of the speed limiter. After that turn the H screw half a turn clockwise (to lean the mixture) and to get the 13.000rpm high end speed. It`s possible that it bogs a little bit because it`s to rich with H=2 turns open.
FredBear
ArboristSite Lurker
Doh!!! I missed that. I didnt read the entire thing and just thought 2 turns out was the stock setting. While cutting I adjusted it down to about 1.5 turns and the saw runs great. This is where I cut with it all day. Thanks again.
FredBear
ArboristSite Lurker
I am going to purchase a tach to do a proper tune. Any chance you have the instructions for a sthil 290 farm boss so I can tune my other saw?
The basic setting for the MS 290 (Walbro HD) carburetor is H=1 and L=1. You may have a version with or without limiter caps, I don`t know. But the basics are the same. The 1 and 1 is the setting without caps. A good tachometer is required to get the right tune.
Make sure to have a proper spark plug and clean air and fuel filters and check the spark arrester that it`s clean. Start engine and warm it up with some cuts. Also make sure to have a properly tensioned chain.
Idle speed: 2800
High speed: 12.500 (is what you should have at the end.)
With the LA screw you turn the speed to 3300 rpm. Now search by turning the L screw (leaner or richer) the highest possible idle speed. If the drop of point is higher as 3700 rpm go back with the LA to 3300 rpm and repeat this step. If you have found the drop off point (highest idle speed) go back with the LA screw to 3300 rpm, after that richen the idle mixture with the L screw back to 2800 rpm and you`re done.
Now the full throttle speed with no load. Give a few seconds full throttle and see where you are (with tach). Turn the H screw (richer or leaner) to get the required 12.500 rpm. I would go 200 or 300 rpm below the 12.500 as safety buffer. (temperature changes, altitude etc.) Done.
If you know from your machine what carburetor you have and what the basic settings are and what the required speed (idle and high) is, you can use this tuning method on nearly every model with diaphragm carburetor.
Make sure to have a proper spark plug and clean air and fuel filters and check the spark arrester that it`s clean. Start engine and warm it up with some cuts. Also make sure to have a properly tensioned chain.
Idle speed: 2800
High speed: 12.500 (is what you should have at the end.)
With the LA screw you turn the speed to 3300 rpm. Now search by turning the L screw (leaner or richer) the highest possible idle speed. If the drop of point is higher as 3700 rpm go back with the LA to 3300 rpm and repeat this step. If you have found the drop off point (highest idle speed) go back with the LA screw to 3300 rpm, after that richen the idle mixture with the L screw back to 2800 rpm and you`re done.
Now the full throttle speed with no load. Give a few seconds full throttle and see where you are (with tach). Turn the H screw (richer or leaner) to get the required 12.500 rpm. I would go 200 or 300 rpm below the 12.500 as safety buffer. (temperature changes, altitude etc.) Done.
If you know from your machine what carburetor you have and what the basic settings are and what the required speed (idle and high) is, you can use this tuning method on nearly every model with diaphragm carburetor.
FredBear
ArboristSite Lurker
again Thanks a bunch. I had the limiter screws on the 290 but I trimmed them when I did a muffler mod. But I just tuned by ear. It has been fine but I want it proper.
Good. With a muffler mod you may have higher rpms now, because of the better flowing. Retune it. It is highly possible that you need more as 1 turn on the screws now, because this tuning setting 1 and 1 is only valid for the stock factory machines without modifications.
