Author Topic: Messed with carb screws, now it won't start  (Read 746 times)

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Offline nl909

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Messed with carb screws, now it won't start
« on: May 19, 2016, 04:13:15 pm »
Howdy, I messed with the carb screws on a Poulan P3816, now it won't start.

I'm wondering how to adjust the screws back to default or such that it will start.

Is it best to turn all the screws IN and then slowly turn then out?

I tried turing the idle almost all the way IN because it seems like that makes it easier to start.

I'm assuming the H screw doesn't matter too much?

So really I'm wondering what to do about the L and IDLE screws.

Any ideas??

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Offline fossil

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Re: Messed with carb screws, now it won't start
« Reply #1 on: May 19, 2016, 05:09:38 pm »
The high screw is the most important as a lean adjustment on that screw will cause your piston to melt. Goodbye saw.

I think with that saw you should start around 2 turns out from lightly turned all the way in on both high and low screws.

Te idle speed screw which sets the idling speed can can be turned up a bit (clockwise).

Start the saw.
The idle mixture screw is set correctly if the saw rev's up quickly from idle when you squeeze the trigger. If it bogs down, Turn the screw out (counterclockwise) until it does. If it does rev up from the starting point of two turns, turn it in 1/8 turn at a time until it bogs when you squeeze the trigger. Open it up a bit so it rev's up quickly. That way your idle won't be too rich.

Set the idle speed screw down or up so it doesn't stall but it isn't going so fast that the chain is moving.

To set the high screw. Make sure the saw is warmed up.

Rev the saw to full throttle for a second. If it is screaming, turn the high mixture screw out until the exhaust note sounds like it's missing at full throttle. That is called four stroking. when the saw is reving free (not in a cut) you should just be on the edge of screaming and four stroking but you must be four stroking. Once the saw is under load (cutting wood)  the exhaust note will clean up and the four stroking will go away.

Once the saw is doing those things you are set to go.

Make sure you have fresh fuel mix in the saw. Don't use old fuel mix.

If you are still having trouble, you may have to get into new fuel lines, a filter and possbly a carb kit.
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Offline 67L36Driver

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Re: Messed with carb screws, now it won't start
« Reply #2 on: May 20, 2016, 09:10:23 am »
Hard to start/no start I've run into quit frequently.  Every time it's because I set the low side too lean.  Open it a half turn.
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Offline Revpop

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Re: Messed with carb screws, now it won't start
« Reply #3 on: May 20, 2016, 04:45:49 pm »
Two things to add:

1.  If you do not have a splined carb tool you will need to obtain one.  It is the only reliable way to adjust these carbs properly in regards to turn counting.
2.  Idle RPM's usually needs to be increased (clockwise) substantially on these chainsaws, especially when new and not fully broken in.  If the idle speed is set too low, it will usually die even if the L needle is properly adjusted at or near the sweet spot of the correct mixture setting.  Agree with the 2 turns out starting point, slightly more counterclockwise if near sea level.


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