Where did you learn to adjust a carburator?

[HuskStihl]

Who says I have???

 

[Big_Wood]

i learned from my dad back when i was 6 years old LOL was very easy with the old 2 series huskies. i admit i tuned a bit rich until i was about 10, then i got confident and lean them out to the edge ever since.IMO a guy really gets good at tuning by ear after he plays with a tach. tuning by ear then checking with a tach really opens a guys eyes. most people who think they know how to tune actually don't. i mean, they know the concept and how to make sure it's not lean but don't know how to put it where it's supposed to be. a rich saw is an unusable saw. alot of times my tune by ear was a few 100 RPM's leaner then spec and never had anything blow up.

 

[a. palmer jr.]

The Stihl saws I've been working on this year have it written on the air cleaner cover what to set the saw at on the H and L screws. That's a good starting point and usually not far off.

 

[pioneerguy600]

I was sitting on the lumber camp steps in the early 60`s surrounded by the likes of Pioneer 600 series, Homelite 600, 663 and the odd C7 with some Mac 1-40 and 1-41 saws. I did my first carb rebuild on a Tillotson HL which was the common chainsaw carb of that time and learned tuning from the chief sawyer who had been a faller but had his leg broke bad, they put him in the mill after that so he didn`t have to work on as much uneven ground. I certainly lost count of how many carb rebuilds I have done and no idea of how many saw I have tuned since. Some say that the newer saws can`t be heard fourstroking but even with my damaged hearing I can hear it and feel it loud n clear.

 

[Chris-PA]

And on a similar note.... I had never come across another type of small engine that has it's top end speed governed by the fuel mixture adjustment. Well, maybe trimmers, but I never encountered such in cycles, snowmobiles and small boat motors. I suppose it's because these all have other variables such as gearing, clutching, and prop pitch that limits them?

Your thoughts?

I guess when fuel is cheap and plentiful and you don't care about pollution or the health of the operator, then maybe a design that pukes raw fuel to limit rpm seems like a good idea. It's certainly simple and inexpensive.

All of these characteristics come from the elimination of air corrector jets on the main fuel circuit when they made these all position carbs. It's what makes them get seriously rich with just a little increase in air velocity ("4-stroking"), and ultimately so rich as to limit max rpm as you describe.

You certainly could design an all position carb that didn't do that, but I admit that would pose a problem - namely how do you set the mixture in the field without rich misfire as a signal? It's not different from anything else, like a lawn mower, but 2-strokes are more vulnerable to lean mixtures. I still think that could have been dealt with, but when they decided to fix the problem they just went with a feedback system (AT/MT), and that probably made sense.

 

[Ironworker]

This one is pretty simple, I believe he's a member here.

 

[user 122190]

His saws oiler sure works. Quite a slick he left on the garage floor.

Looks complex/confusing. My take away, run it till is screams (lean), back off till it stumbles a bit. Set the low so it idles.

This one is pretty simple, I believe he's a member here.

 

[Rx7man]

I guess when fuel is cheap and plentiful and you don't care about pollution or the health of the operator, then maybe a design that pukes raw fuel to limit rpm seems like a good idea. It's certainly simple and inexpensive.

All of these characteristics come from the elimination of air corrector jets on the main fuel circuit when they made these all position carbs. It's what makes them get seriously rich with just a little increase in air velocity ("4-stroking"), and ultimately so rich as to limit max rpm as you describe.

You certainly could design an all position carb that didn't do that, but I admit that would pose a problem - namely how do you set the mixture in the field without rich misfire as a signal? It's not different from anything else, like a lawn mower, but 2-strokes are more vulnerable to lean mixtures. I still think that could have been dealt with, but when they decided to fix the problem they just went with a feedback system (AT/MT), and that probably made sense.

Would it be possible to modify a Tilly carb for an air corrector jet?... I've got a few spares around I could trash in some attempts if I had any guidelines on it

 

[Andyshine77]

I'll add my video to the list.

 

[Chris-PA]

Would it be possible to modify a Tilly carb for an air corrector jet?... I've got a few spares around I could trash in some attempts if I had any guidelines on it

I'm sure it would be possible, but it would take some considerable development work, most of it trial and error. Not to mention that this would be an air passage into the main fuel well, so it likely would compromise the all-position nature of the carb. And then how would you set the mixture?

I considered it but decided not to bother. I would want to be paid for doing that kind of work, but it isn't my field.

 

[Snowchaser]

I grew up tuning sleds and saws too. If you go straight to tillotson, walbro, etc websites they have pretty cool breakdowns of what the carb is doing at given points in the throttle cycle. May not help tuning other than the main needle arm, but is still interesting.