661 4 stroking in the cut

[altair]

My 661 is just out of warranty, so I did a quick muff mod the other day.

Opened up the small round exit hole out of the muffler to twice what it was, and got rid of some of the cage in the muffler..not really a cage so to speak on these, but I cut half it out.

Its incredibly loud now..I'm almost tempted to put a standard one back on!

But problem is now its 4 stroking constantly, even in the cut. Gets run on Stihl Ultra at 40:1,currently has a 25 inch bar.
Air filter gets cleaned every use.

What have I done? I would call this muff mod conservative compared to what I've done on the 440 and old 38, they run beautifully.

Does it need a reset maybe? I'm sure the local Stihl shop will condemn my muff mod if I take it in there...lol.

On another note I bought a new MS180 the other day, nice wee saw but bit gutless, do these non adjustable carbs allow a little muffler mod, or not? Can't be bothered going through the hassle of buying a new carb etc to be honest.

Cheers

 

[Little Al]

You have Modded the muffler I'm not to "oh faye" with these saws is the carb adjustable or one of the self adjusting "jobbies" if it has a H & L adjustment needles try turning the H in(clockwise) if it has limiters on the needles you may have to remove/modify them you,will probably have to adjust both H & L screws to get the correct settings for best running

 

[jr27236]

You have Modded the muffler I'm not to "oh faye" with these saws is the carb adjustable or one of the self adjusting "jobbies" if it has a H & L adjustment needles try turning the H in(clockwise) if it has limiters on the needles you may have to remove/modify them you,will probably have to adjust both H & L screws to get the correct settings for best running

Sounds like he has an A/T. I unfortunately have no experience with these carbs, but I'm sure you will have plenty of helpful replies soon. At least its not running lean[emoji1]

 

[jmssaws]

It needs reset.

 

[jmssaws]

90 seconds on choke shut off
90 seconds on run shut off

 

[blsnelling]

1. Put the master control switch into the start/choke position.
2. Start the saw. Do not touch the throttle.
3. Let it set there and idle for 90 seconds.
4. Move the master control switch directly to off, while not touching the throttle.
5. Start the saw and go cut wood.

 

[altair]

Thank you guys, will do a reset tomorrow,appreciate the advice. Cheers!

 

[jr27236]

Thank you guys, will do a reset tomorrow,appreciate the advice. Cheers!

Let us know how you make out.