MS261CM M-Tronic Issues and Many GFY’s

[RI Chevy]

Can the 261 jet be changed out or drilled a little bigger?

 

[00wyk]

Maybe Randy can move that to the 'sausage thread'.

 

[tree monkey]

sound to me that it's time to pluck them chicken feathers and experiment on the carb.
the old saying goes, you gotta pay to play

 

[tree monkey]

it's possible that the strao timing is now too long allowing to much fresh air into the cylinder. adding more intake duration ma only make it worse with added spit back. if it was all about heat it should score the piston.

 

[drf256]

The other way around.

Because of crank angle, the stratos move less than the intake floor.

 

[drf256]

I lowered popoff, did nothing

More may have helped, or drilling the carb jet

 

[drf256]

SOHCAHTOA

 

[00wyk]

Y=MX+B is usually what we use in forestry tho.

Speaking of heat - I was a bit paranoid since this poor 241 lost it's crown in a forestry accident, and aired out the lid not long ago. Whether it makes any difference, *SHRUG*.

 

[sawmikaze]

I think having your own personal control over a saw is still better though Mike. I think this Mtronic/Autotune stuff is for EPA. Being able to tune is better sometimes.
Just me...

I agree, but i think it takes the operator error out for a few things too.

You could *b-word about anything really..it all has it's up's and down's

 

[sawmikaze]

Don’t underestimate yourself.

You're right .. I can do better.

 

[Mastermind]

You could *b-word about anything really..it all has it's up's and down's

I like turtles.

 

[sawmikaze]

Found this pic.

View attachment 174128

Selfies are really cute.

 

[sawmikaze]

I like turtles.

#metoo

 

[Definitive Dave]

It’s not the port timing, or squish or fuel itself.

The MT on this particular saw can’t fatten up the tune enough to control rpm on a saw that gets too hot. Two reasons why:

Fuel mix too thick to flow enough

Saw heat above capacity that MT is programmed/designed to handle.

So if saw gets too hot from too much compression regardless of squish, the system tries to fatten up the tune. If the fuel mix is too thick of a viscosity, it can’t flow enough fuel to rectify the situation regardless of how fat the MT tries to make the tune. Then all sorts of bad stuff starts to happen in the MT computer.

So in the right situations, compression, ambient temp and fuel mix won’t affect anything. But take too much out of the squish band and make the chamber too small and There’s a problem Houston.

Saw run around 185psi stock. Cutting the band for a nice flat tighter squish is likely all that’s needed. Pull 50 out of the chamber and keep squish at 15 and the saw likely has 275 psi and gets too damn hot.

Bigger MT saws have bigger jets, needles, seats, etc-So they likely aren’t affected by the issue as often.

I’d venture to say that saws that don’t have the issue have either better cooling systems, lower factory compression or a fuel system that’s large enough to flow more.

Drill the carb for more better fuels?

 

[tree monkey]

Drill the carb for more better fuels?

there ascared to

 

[Mastermind]

there ascared to

Have you drilled an mtronic carb?

 

[tree monkey]

I haven't needed to randy, but I will when the time comes, I haven't had this issue with any m/t saws

 

[Mastermind]

I haven't needed to randy, but I will when the time comes, I haven't had this issue with any m/t saws

Neither have I. Out of the 160 MS261s I've done, none have ever needed the carb dicked with.

 

[ABarrick]

This thread got me thinking. I had a 441cm a few years ago that was the opposite. It fed too much fuel all the time. I raised the pop off, lowered metering lever and neither made any difference. It was just rich all the time. Tried resetting it many times. Not unusable, but way out of tune. Never did figure it out. It got traded in on a 461 after a brief love hate relationship.

 

[huskihl]

Neither have I. Out of the 160 MS261s I've done, none have ever needed the carb dicked with.

I don't know that the carb "needs" to be dicked with under normal operating circumstances. I think most people are going to use these to cut 8 inch wood and in that case this problem would never arise. With a 20 inch bar buried it takes five successive cuts to make it happen