MS660 intella carb messed up?

[Butch(OH)]

My low hour 2 year old MS660 has developd a wierd problem in that as the air filter gets dirty it gets lean. I am not talking super dirty filter but the dust and debris from 2-3 tanks of fuel. It's like the smart carb is over reacting to a little filter restriction. Started doing this maybe 20 tanks ago not bad enough to get a screwdriver out but noticeable. Yesterday I was cutting some old dry dusty Hackberry and it got lean enough that I ran the H screw out a tad to finish up and it was close to perfect by ear, no tach. Cleaned the filter when I put it away. Today I started up with the cleaned filter and it was so rich that I had to reset the carb to even use it. I am talking about 1/2 of a turn ( I have the limiters out of the carb) Since this is all happening bass dackwards from common sense I am guessing an intella carb problem? If so what to fix? Thanks in advance.

 

[epicklein22]

since you have the limiters off, maybe the needles are moving on their own. Check your setting you have now, record it and then next time it leans out, find out where it is set compared to optimal setting.

 

[blsnelling]

since you have the limiters off, maybe the needles are moving on their own. Check your setting you have now, record it and then next time it leans out, find out where it is set compared to optimal setting.

+1. You need to cut the limiting tabs off of the caps and reinstall them to keep the screws from moving due to vibration.

 

[ironman_gq]

could always get a different carb from a non intellicap saw and run it like a normal saw

 

[blsnelling]

Shouldn't need to.

 

[ironman_gq]

He shouldnt need to but it would get rid of any problems with his current setup and simplify troubleshooting in the future

 

[epicklein22]

Intellacarb is a great idea. It really does work......my dealer said he was at a stihl meeting for mechanics and they had a saw running with a tac on it. Next thing they do is pour an entire bag of flour over the air filter, covering it. The tac still had the same reading. Pretty impressive to me.

 

[Tzed250]

.


Plenty of info on the site stating that the EPA carbs should not be run without the caps (trimmed or not trimmed).


.

 

[Butch(OH)]

Two titless caps installed tonight, thanks. I hope that is it but vibration doesnt explain the changes over night?

 

[056kid]

since you have the limiters off, maybe the needles are moving on their own. Check your setting you have now, record it and then next time it leans out, find out where it is set compared to optimal setting.

i also experienced the same thing when i took the limiters off.

Did you notice how easy it was to turn the screw? I dont think there are any springs.

 

[Tzed250]

There are, in fact, no springs...

 

[Butch(OH)]

OK, spent an afternoon with the 660 yesterday (6 full tanks of fuel) and even with the caps installed (the needles are not turning I checked) I had to adjust the carb three or four times to keep it running correctly. As the day went on the saw first went rich, then back and forth from rich to lean. Probaly half a turn of adjustment total. Ended the day about where it started for adjustment and was running OK. Saw idles great, I can turn it side to side or up and down and idle does not change so I assume? no air leaks? Only the high speed is being affected. What next? carb kit?

 

[Fish]

I think you are jumping the gun and blaming the carb and dirty air filter.

Playing with the carb adjustment to rectify a saw running problem is
never a good idea,so you should start looking for the problem.

 

[Butch(OH)]

I think you are jumping the gun and blaming the carb and dirty air filter.

Playing with the carb adjustment to rectify a saw running problem is
never a good idea,so you should start looking for the problem.

Suggestions?

 

[Fish]

Yes, sorry, had a lot of e-bay tasks this morning. I would go ahead and pull the carb, and check the fuel and impilse lines. Disassemble the carb, and
inspect, and clean out the gunk. Visually inspect the passage under the
needle, and look at the viton tip. You may just find the passage under the
needle is partially clogged, and that is all. But with the newer Stihls, the
fuel lines get cracked and let in crud, so if that is the case, you would
need to go through the carb as well.

If the diaphrams look stiff, etc, you should change them out as well.

 

[pgg]

alternating between rich and lean, a dodgy/sticking fuel tank breather will cause that same problem too