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Discussion Starter #1
Ariens 8/32 from 1975 here. Trying to get a better understanding of how to properly set the low speed fuel mixture. It has a new carb about 2 yrs ago. Runs solid under load and is a mule. With no load it surges so I think it needs adjustment somehow on the low speed fuel circuit. Is there a method for adjusting the main mixture and the low speed mixture on full load vs no load or how is this done properly?
 

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Ariens 8/32 from 1975 here. Trying to get a better understanding of how to properly set the low speed fuel mixture. It has a new carb about 2 yrs ago. Runs solid under load and is a mule. With no load it surges so I think it needs adjustment somehow on the low speed fuel circuit. Is there a method for adjusting the main mixture and the low speed mixture on full load vs no load or how is this done properly?
I would suggest YouTube videos. DonnyBoy (think that is his handle ) has good videos on adjusting mixture screws. Some may be on a chain saw, but for the most part, the process is the same.

Not rocket science once you watch the video. Basically, clockwise turning of the screw limits the fuel, which will make it run leaner, and the opposite does the opposite ! Kind of fun once you get the hang of it. You'll be looking for engines to work on !
 

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idle muxture screw 1 1/4 turns out base setting
high speed screw 1 1/2 turns out base setting
warm it up set hi speed mix screw turn in until it runs ruff then out till it runs ruff then set it in the middle
you can adjust slighty to your conditions warm= a lil less rich cold a lil more rich
idle mixture should be close
then adjust idle speed
 

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Set the basic setting. Screw the needle in all the way, not tight, just until it stops. Then 1-1/2 turns out. Same for the high speed adjustment under the carb.

Start and warm up the machine, at full throttle adjust the high speed mixture until rpms peak at their highest. Adjust slightly in and slightly out then settle in the middle.

I then raise the idle by turning in the idle screw to around 2400rpms. I use a hand held tach that just needs to be held close but by ear is fine.

Then adjust the mixture screw in or out until the engine rpms peak their highest. You should adjust the screw in and out and settle in the middle.

Then drop the idle to around 1800-2000 by screwing out the idle screw. (I think that’s spec)

To test the low speed mixture, idle the machine and move the throttle quickly back to full speed. If it doesn’t choke and ramps up in RPMs immediately then you’re good. A momentary stumble isn’t a problem.

If it chokes then make a 1/8 of a turn adjustment at a time until it accelerates properly.

In practice it take me under a minute.
 

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right i didnt say to raise idle 1st before adjusting as he might raise to high tuff to know by ear
i use a tach myself
better to use the slow to fast as a guide without the tach imo
as jt said make sure nothing is clogged or you will be doing all this again
 

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easy way, on warm engine, adjust high idle, wide open throttle, until it sounds good as too far in or out engine sounds like crap.
then lower throttle lever to just before kill switch is engaged, adjust low idle air screw, not the idle butterfly set screw, adjust until engine sounds good, then bring throtle lever back to wot and adjust the low idle air screw until engine sounds good.
on wot engine uses both low and high speed air mix screws.
this assumes carb is cleaned and has good fuel flow from tank.
 

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Discussion Starter #12
Thanks for all the info guys. I took out the low mixture screw and sprayed carb cleaner in there and let it sit for several minutes. Low mix screw is ~1.5 turns out and the main mix well that is easy to adjust at high speed to where it needs to be. This is not the OEM carb but a replacement that appears to be identical. It idles nice and smooth but I'll have to see tomorrow in the snow clearing if the high speed no load mix seems correct or not. I think I understand that surging at high speed no load is a signal of less than needed fuel through the low mix circuit.

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