Problematic MS661

[blsnelling]

I cured mine with needle height and proper adjustment of the tiny set screw that adjust the opening of the fresh air butterfly.

 

[redbull660]

I think I mentioned it earlier, but this only showed up after I removed the baffle in the muffler and further opened it up. I have another muffler to throw on to test that, but am unwilling to leave it that way. It improved performance. We just have to find a way to work around it.

my guess - you have an imbalance in the system. Since you have exhaust opened up so much. So doing max flow and getting more air in will fix imbalance.

Or

you keep the same stock air filter setup and correct the imbalance by going back to a more restricted muffler. ie with a baffle and not as big of a exit port.

 

[blsnelling]

Bottom line, it's a carb tuning issue that the MTronic can't handle. That's frustrating! All this saw needs is the tweak of an L needle.

 

[redbull660]

Just because you can tune it out with a regular carb...I don't think means it (the imbalance) shouldn't be corrected.

in other words - if you have that much going out and it needs that much L to tune it, ...maybe instead of just tuning it out we WANT more air coming into the system.

 

[blsnelling]

It should be able to compensate.

 

[big t double]

at this point id probably try punching it in the face...right in the damn face. throat punches usually correct things too....just throwing it out there.

 

[redbull660]

fyi - i fixed the idaho saw by doing this. It had half the baffle cut out and a huge exit port. I put a stock muffler back in, did the reset, it took about 2 tanks but the bog went away. I then tried the 7/8" opening muffler and never had a problem.

I had the same problem with morparmyway's muffler when i tested it... which is opened up gigantic. But he has countered it with more air flow into the system via his air filter/ max flow filter mod.


This is why I think the 7/8" diameter hole is as large as u can go with a stock saw.

But the real question is. What is faster?

7/8" with + stock air filter setup?

OR

larger than 7/8" exit port + maybee the baffle removed? + max flow air filter mod

----------------------------------

at this point it would be an easy thing to test.

my 7/8" + stock filter setup
vs
morparmyway's muffler + air filter mod

 

[Moparmyway]

Unquestionably ............ more air in = mo power out

 

[blsnelling]

Is this to suggest that we should stop muffler modding otherwise stock saws? Of course not. Why don't other saws display these symptoms? Because we tune the carb after the mod and enjoy a saw that actually has better throttle response. I stand by my statement that this is a carb tuning issue.

Now, that's not to say that a better air filter isn't a good idea and may show additional gains. I'm all for moving in that direction. I'm simply saying that's it's a misnomer to call this an imbalance. It's simply something that MTronic can't handle.

 

[Moparmyway]

There aint another big cube saw out with electronics.
Sucking gobs of air and trying to electronically manage the fuel curve with a restricted HD2 isnt as easy as some wish it to be

 

[Mastermind]

Over thinking a simple issue at it's finest.

 

[Moparmyway]

Over thinking a simple issue at it's finest.

Isnt this how gains were gotten in the first place ?

 

[redbull660]

ok i'll try one more time...

imbalance - normally carb lets you tune it out. Should you tune it out? No. You should add more air. If you do tune it out then your still not ideal power. 661 just doesn't let you do that. Right now it's saying restrict the out flow (muffler). Or give me more air.

put the (more restricted ) muff porche965 is sending you, on it. and it'll fix it.

OR

put the max flow on and it'll fix it.

all u gotta do is fix the imbalance. one side of it or the other. The question is which side makes more power? I think that is very obvious. Put the max flow on your saw.


ps. you'd probably have the SAME problem or some other problem if you kept the muffler stock and put the max flow mod on the back. just another imbalance.

 

[SquareFile]

Isnt this how gains were gotten in the first place ?

I agree. If test weren't being done by people then ported 661's using h1r @32:1 wouldn't be any faster than stock 661's using Wal-Mart oil @ a couple glugs:1

 

[blsnelling]

put the (more restricted ) muff porche965 is sending you, on it. and it'll fix it.

OR

put the max flow on and it'll fix it.

That's exactly what I'll be doing. I'm just waiting on the filter element to show up. The muffler is here.

 

[blsnelling]

Over thinking a simple issue at it's finest.

Enlighten us.

 

[Andyshine77]

Is this to suggest that we should stop muffler modding otherwise stock saws? Of course not. Why don't other saws display these symptoms? Because we tune the carb after the mod and enjoy a saw that actually has better throttle response. I stand by my statement that this is a carb tuning issue.

Now, that's not to say that a better air filter isn't a good idea and may show additional gains. I'm all for moving in that direction. I'm simply saying that's it's a misnomer to call this an imbalance. It's simply something that MTronic can't handle.

I've ran saws without any filter at all numerous times.[emoji6] Yes more air is better that's not the issue. What is a problem, is the fact we can't use a little orange screwdriver to fix this problem, if you want a really strong saw to run with its stock air filter.

Remember most people that use saws professionally don't even know or care about ported saws, so it may not be a problem, or a problem Stihl even cares about. But in my mind, and if this is in fact what's causing the bogging issue, the filter is too small/restrictive.

 

[blsnelling]

What filter is on a new MS880?

 

[big t double]

hd2 0000 140 4402. same as 660

 

[blsnelling]

hd2 0000 140 4402. same as 660

Hmmm.