Author Topic: Vapor lock on a hot day.  (Read 555 times)

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Offline fossil

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Re: Vapor lock on a hot day.
« Reply #10 on: November 02, 2016, 08:57:00 pm »
Gas boils at temperatures from 95F to 400F. The tank vent is important as a vacuum in the tank will lower the boiling point considerably. Make sure the vent is letting air in and not out. When the cap is removed you can hear the hiss of air. The question is which way is it going. Not recommended to check with a match unless you have a willing friend handy.
Higher elevations just make the issue worse. Winter formulated gas does as well.

Cory, if you run the tank dry, fill it up, cap it and shake the saw for a bit. That will build pressure in the tank and get the gas up to the carb faster,

I also have some filters I bought from Carbtech that have check valves of some kind in them to keep the gas from draining back.
Tim
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Offline Al Smith

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Re: Vapor lock on a hot day.
« Reply #11 on: November 02, 2016, 09:06:45 pm »
Funny part about that hot weather .I had a cooler full of cold water and drank at least a half dozen during that day never peed once .
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Offline 3000 FPS

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Re: Vapor lock on a hot day.
« Reply #12 on: November 02, 2016, 10:49:42 pm »
Funny part about that hot weather .I had a cooler full of cold water and drank at least a half dozen during that day never peed once .

That is funny Al but I have to admit to the same experience.   Sweat it out instead.
PP 505, 475, 445.

Offline 3000 FPS

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Re: Vapor lock on a hot day.
« Reply #13 on: November 02, 2016, 10:54:20 pm »
Gas boils at temperatures from 95F to 400F. The tank vent is important as a vacuum in the tank will lower the coiling point considerably. Make sure the vent is letting air in and not out. When the cap is removed you can hear the hiss of air. The question is which way is it going. Not recommended to check with a match unless you have a willing friend handy.
Higher elevations just make the issue worse. Winter formulated gas does as well.

Cory, if you run the tank dry, fill it up, cap it and shake the saw for a bit. That will build pressure in the tank and get the gas up to the carb faster,

I also have some filters I bought from Carbtech that have check valves of some kind in them to keep the gas from draining back.

I think that in the future I will just ovoid cutting up that high in the mountains when I know it is going to be hot.   Some saws could be more inclined to have this problem than others but I think it will eventually happen to any saw when the right conditions are met.   

I like your tip Tim about shaking the saw to get pressure built up in it and driving fuel up to the carb.
PP 505, 475, 445.

Offline Eccentric

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Re: Vapor lock on a hot day.
« Reply #14 on: November 06, 2016, 05:03:00 pm »
Gas boils at temperatures from 95F to 400F. The tank vent is important as a vacuum in the tank will lower the boiling point considerably. Make sure the vent is letting air in and not out. When the cap is removed you can hear the hiss of air. The question is which way is it going. Not recommended to check with a match unless you have a willing friend handy.
Higher elevations just make the issue worse. Winter formulated gas does as well.

Cory, if you run the tank dry, fill it up, cap it and shake the saw for a bit. That will build pressure in the tank and get the gas up to the carb faster,

I also have some filters I bought from Carbtech that have check valves of some kind in them to keep the gas from draining back.

The OEM Poulan 5200/5400/8500 fuel filter is like that.  Is Carbtech the site with the cheap carb rebuild and DG kits?  I need to check out those filters....
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.

Offline Eccentric

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Re: Vapor lock on a hot day.
« Reply #15 on: November 06, 2016, 05:04:02 pm »
This is the site I was thinking of.


http://www.carbtech21.com/Default.asp
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.
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