Help with Stihl 031 av

[a. palmer jr.]

Thanks for the input, fellas.



Yessir. Duly noted.



I agree on the coil probably not being the problem and wouldn't consider a couple hundred ohms out of spec "bad" at that range. Lower range = higher percentage out of spec, of course.

But as to the original question about the MegaFire module itself. Not sure it's any different than the Stens, Oregon, etc. Look the same to me. I suppose a timing light setup would indeed be the way to go for a definitive answer on any or all of em. Matter of fact, it would be cool to test all the available chip variants, polarity reversals, and flywheels back to back with an actual timing light setup to get to the bottom of the subject once and for all. One thread. One post. All the 031 chip conversion information right there in one place. Would make too much sense. LOL



Anything special about your timing light or will any old cheapie do the trick? A dial gauge or degree wheel to get TDC would probably be the way to go there, too.

Nothing special, mine cost about $20 so it's not the best. I have to rig up a 12v power supply or use a battery to run it though. It doesn't have to be real precise, I just take the spark plug out and stick a pencil or something in the hole and run it up to TDC and mark the flywheel and the engine with a magic marker then make another mark for about 20 or so degrees (whatever the spec is) before TDC, leave the plug out and turn it over with the drill and you'll soon see what you have.

 

[PogoInTheWoods]

Cool. Thanks. Think there's a timing mark on the case for 22 degrees (?) BTDC for reference.

And just for the record, (not that it probably matters now)...,

the spec is 0.7 - 1.0. The secondary reading in K ohm is 7.2 x 1000-7200, the spec is 7.7-10300.

..., those are actually 032 coil specs. The 031 is 0.8 ~ 1.1 and 6.5 ~ 8.0K, so the coil previously in question was fine.

 

[PogoInTheWoods]

stick a pencil or something in the hole and run it up to TDC and mark the flywheel and the engine with a magic marker then make another mark for about 20 or so degrees (whatever the spec is) before TDC,

'Nuther new question in an old thread...

Once TDC is determined, how does one then accurately measure the specific flywheel advance required to achieve the desired 25 degrees BTDC at 8000RPM (since there's also clearly an advance built into the coil to achieve the spec) without the saw running and using a timing light on the PTO side with a tach?

I found an older thread where Lakeside actually had pics of both points and electronic flywheels for comparison but it was pre-hack and the pics are now gone. Said he was also going to do some specific timing measurements which would have presumably translated into actual degrees of flywheel advance (vs. piston movement in mm) using a degree wheel to achieve the desired BTDC firing position of the piston.

Seems like 30 degrees of flywheel advance is the general consensus. Just wondering if anyone has spent the time to measure specifically how much is required for the chip to fire at 25 degrees BTDC at 8000RPM..., (or what the timing advance would be at an attainable RPM with a drill using a timing light).

I'm at what seems to be around 30 degrees (or more) of f/w advance and still have a stutter at WOT that doesn't want to go away by leaning it out normally. Matter of fact there's a 'break point' where it sorta wants to be nice and then just takes off way too high and has to be dialed back. It'll idle all day long but isn't quite right there either.

Would really like to get this thing nailed down and am getting tired of removing and re-installing the damned recoil in a trial and error method.

Anyone have both points and electronic flywheels handy for some pics and measurements? Or maybe have Lakeside's pics stashed somewhere?

 

[a. palmer jr.]

I haven't had an 031 or any parts for 2 or 3 years now. I think I ended up just putting mine at 3/4" measured at the outer edge of the flywheel. I guess the right way is to measure the circumference and divide it by 360, that would give the measurement for one degree then add 22 of them to the tdc mark, before tdc, that is...better check my thinking, it's late...