New MS461 - Strange Tuning

[pwheel]

Got a question, please.
Picked up a new ms461 today. Put a tach on it when I got a chance to check the tune. Shop manual specifies 13k rpm by tach, then 1/8 turn lean (without tach) on the high needle to get to 13.5 rpm +/-. Found that the limiter cap wouldn't allow me to richen the mixture to 13k and the saw was bouncing off the rev limiter. Removed and replaced the limiter cap three times to finally get an additional 3/4 turn richer. Now the saw tops out at 13k, which is where I would like to tune it out of the box. Easy 2-stroking in wood, which sounds about right to me for break-in.
Anyone else see a brand new stock ms461 running lean bouncing off the rev limiter? 3/4 turn is a lot. Am I missing something?

 

[stihl livin]

Is the coil limited on the 461? I thought they need a different coil when ported.

 

[huskihl]

There’s an auxiliary main jet inside the carburetor that provides about 80% of the fuel. All your H jet does is provide the additional 20%. So turning it a bunch doesn’t have as much effect on the overall tune. When you remove the limiter, just trim the tab off so you have full adjustment

 

[pwheel]

Is the coil limited on the 461? I thought they need a different coil when ported.

Yes. The stock coil is limited.

 

[pwheel]

There’s an auxiliary main jet inside the carburetor that provides about 80% of the fuel. All your H jet does is provide the additional 20%. So turning it a bunch doesn’t have as much effect on the overall tune. When you remove the limiter, just trim the tab off at so you have full adjustment

Thanks. If I have to go through this again, I'll trim the tab on the limiter.

 

[drf256]

What kinda mix ratio and oil are you running?

It’s possible that if it’s too viscous it’s could be not flowing well, especially if it’s cold out.

What’s your elevation?

The HD50 has smaller jetting than the other 1128 series HD carbs.

 

[Glock37]

Change coil to a 1314,1312. Coil they are unlimited easier tuning


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[pwheel]

What kinda mix ratio and oil are you running?

It’s possible that if it’s too viscous it’s could be not flowing well, especially if it’s cold out.
What’s your elevation?
The HD50 has smaller jetting than the other 1128 series HD carbs.

Thanks for the questions.
The saw came from the shop with 50:1 mix w/ Stihl orange bottle oil & premium gas. I run 50:1 Stihl Ultra & premium gas with a splash of Star Tron. 34º temperature yesterday afternoon; 250 ft. elevation above sea level. 13,000 rpm max now according to my tach. Like I said, the motor sounds right to me in the cut for break-in tuning. If I ever decide to port the saw, I'd definitely change the coil to unlimited.

 

[species8472]

I have a 660 coil on mine works a treat.

 

[pwheel]

Thanks for the replies. I think I've got it sorted, partly by tach and partly by ear. Also have an ms440 and ms460 to compare. Still wondering if these saws are tuned lean at the factory with max rpm governed by the coil for emissions compliance or whether I got one that slipped by QC, Anyway, it runs great now; no complaints.

 

[huskyboy]

Still wondering if these saws are tuned lean at the factory with max rpm governed by the coil for emissions compliance

Yes. The limited coil is more for keeping the bottom end alive for longer. Durability. A big majority of newer saws have limited coils.

 

[drf256]

They fatten a saw up also on the top end.

Think about what happens with an open throttle plate and no ignition. The engine sucks in mix it doesn’t burn.

 

[pwheel]

They fatten a saw up also on the top end....

That makes sense for durability. As for my 461, though, the opposite turned out to be the case, where the maximum rpm was being limited by the coil, not the air/fuel ratio, and the saw was running hot and lean when I got it. I had to remove the carb and reset the high speed needle/limier cap in order to get the max high speed air/fuel ratio in spec according to the Stihl service manual. Runs much cooler now and sounds and feels like my other 1128 series saws. I'm hoping that this saw was the one that got by final factory inpection, as I can't imagine dealers taking apart 461's in order to tune them to factory spec. Or perhaps all 461's are leaving the factory lean-tuned to meet emissions standards with the expectation that they will be re-tuned to published factory specs down the road. OK, so I'm suspicious...

 

[pwheel]

There’s an auxiliary main jet inside the carburetor that provides about 80% of the fuel. All your H jet does is provide the additional 20%. So turning it a bunch doesn’t have as much effect on the overall tune. When you remove the limiter, just trim the tab off so you have full adjustment

Yes. Thanks. The head shop tech told me the same thing this morning. Also told me that these saws are tuned hot and lean at the factory for emissions compliance, and recommended removal of the high speed cap limiter and tuning to 13k rpm for break-in and longer service life.