Hot weather chainsaw tuning??

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redhawk23

redhawk23

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southern wisconsin
Hi,
I have a new Makita 4300 (fomerly Dolmar 421) that only has a few hours on it. I was using it the other day in 70 degree temps and it wouldn't restart unless I let it cool down for a half hour or more. The saw is basically brand new: clean, sharp, fresh ethanol free gas. New. I have had this problem before with other saws but at higher outside temps, including a Husky 555, a Dolmar 421 and a Stihl 362 on hot days. Does the carb need to be tweaked? What is going on? Also, I have that little window closed off keeping the heat from the carburetor.
 
Ted Jenkins
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Apr 18, 2016
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Twin Peaks
Some facts about about warmer weather that do not really make sense. Warmer weather means less air to the engine or a richer mixture to the combustion chamber. However dissapating heat is also very important. The biggest tool one has to compensate for hotter conditions are carb adjustments. Running a richer fuel air ratio means less effeciency to the combustion chamber which produces less heat thus combating a hot saw. Merely adding more oil the the premix does what one thinks will not happen which makes for leaner fuel air mixture and thus more heat. The oil will cool the combustion process a little by being present but not much. Thanks
 
lone wolf
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Prowling The Pine Barrens
Hi,
I have a new Makita 4300 (fomerly Dolmar 421) that only has a few hours on it. I was using it the other day in 70 degree temps and it wouldn't restart unless I let it cool down for a half hour or more. The saw is basically brand new: clean, sharp, fresh ethanol free gas. New. I have had this problem before with other saws but at higher outside temps, including a Husky 555, a Dolmar 421 and a Stihl 362 on hot days. Does the carb need to be tweaked? What is going on? Also, I have that little window closed off keeping the heat from the carburetor.
Two words Winter Gas.
 
SteveSr

SteveSr

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Mar 3, 2003
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Raleigh, NC
Hi,
I have a new Makita 4300 (fomerly Dolmar 421) that only has a few hours on it. I was using it the other day in 70 degree temps and it wouldn't restart unless I let it cool down for a half hour or more. The saw is basically brand new: clean, sharp, fresh ethanol free gas. New. I have had this problem before with other saws but at higher outside temps, including a Husky 555, a Dolmar 421 and a Stihl 362 on hot days. Does the carb need to be tweaked? What is going on? Also, I have that little window closed off keeping the heat from the carburetor.
What you are experiencing is vapor lock likely caused by using a winter grade fuel. Heat can cause this or make it worse. Everything from changing the fuel source to enriching the mixture to letting it idle before shutting it off will likely help. There have been several threads on this forum recently eliciting such issues. Happens every spring.
 
lone wolf
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Oct 5, 2009
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61,155
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Prowling The Pine Barrens
What you are experiencing is vapor lock likely caused by using a winter grade fuel. Heat can cause this or make it worse. Everything from changing the fuel source to enriching the mixture to letting it idle before shutting it off will likely help. There have been several threads on this forum recently eliciting such issues. Happens every spring.
Wait till the temp goes up !
 
holeycow

holeycow

Dirt, Air, Water, Sun; Seeds.
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What do loggers do all day? Loggers work while homeowners play.
The Logger buys professional saws and the homeowner buys Makita 4300s and come on here and ask questions!
I guess you don'thave a clue about a Makita 4300. It's a very well constructed, mag case, adjustable oiler, open port saw that will run with and even outrun some decent 50cc saws. My Dolmar 420 is a beautiful little saw.
 

J D

ArboristSite Guru
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Apr 19, 2020
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NZ
Ok... Ignoring the last few posts & attempting to get back on topic...
Winter fuel won't be doing you any favors so avoid it if possible. Ideally run a little extra oil (40:1 quality synthetic) & tune a bit rich.
Don't up the oil without tuning it for the mix you intend to run. Tuning should ideally be done with a tacho & in your case (new saw, hot running) set to a few hundred rpm below max.
Madsen's has some good directions on tuning by ear. In a pinch you could probably just turn the H screw OUT 1/8 of a turn. Your adjustment screws may be tamper proof, may have limiters on them, making adjustments may void your warranty & if you get it wrong you may wreck your saw.
Good luck :)
 
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