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Why won't saws start when hot?!

Nutball

TreeHouser
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Apr 4, 2015
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Mt. Juliet, TN
This seems to be a pretty common issue at least in my experience. I used to rarely if ever run chainsaws in the hot summer because it is too hot to work. I do it more now and of course know others that do obviously because we all need work. Recently my echo 271t which would always start in two if not just one pull when warmed up now takes 5-10 pulls. Is it vapor lock, fuel nearly boiling in the lines or fizzing out when it enters the carb causing a lean mixture? For the first few pulls it doesn't fire at all, then sometimes it does that thing where you hit full throttle and it wants to die. I'll go to check to see if it ran out of gas to have the gas boil out all over. A guy I work with will give me a saw to fix complaining it doesn't run right and is hard to start. I usually have no trouble with it, and run it till it's hot without issues, give it back, and he says it runs great for 20min then doesn't start.

Do you guys who work in hot locations have this much trouble with starting hot saws? What is the solution? Do you know of any chainsaw models that tend to have this problem more than others, or is it pretty much with any? The only thing that comes to mind is trying 100% gas 93 octane, and add a little diesel to hopefully increase the boiling point.
 

woodworkingboy

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Aug 16, 2008
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Nippon
Saws that stop running or won't start when hot can be an ignition coil going bad. When hot and not starting you might pull the plug to check to see if you are getting a spark.
 

Skwerl2

Rodent Aviator
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May 25, 2017
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central Florida
Yes, it's vapor lock. Been dealing with it for 35 years here in central Florida. You can do a couple things to minimize the issue, mostly just being aware that it is an issue and avoiding triggering it.

First, I seem to have less issues with it when I use premium gas for my mix. It's 50 cents a gallon more than regular and if you burn 5 gallons of mix per week it's $2.50 per week. Most people use a hell of a lot less than that.

Next, avoid leaving your saws or gas in the sun. I have closed boxes on my truck. If you don't, keep your saws in the shade somewhere.

If your saw vapor locks, open the gas cap to relieve the pressure and then fill it up with cooler gas out of the gas can. If the saw has a primer then pump it until the primer ball is full of gas instead of air. When you start it you may need to play with the choke while hitting the throttle until you can suck enough gas into the engine to run right.
 

pantheraba

More biners!!!
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near Atlanta
Good description of how to handle that...thanks. I thought I was getting that same problem today on a job. On a whim I checked the air filter (on my MS 290) and it was pretty cruddy. Cleaned it but still would not run more than a few seconds.

I adjusted the L and H screws...ran them all the way in then back the proper amount. Saw started running perfectly. Maybe trash in a jet? Whatever it was that fixed the problem.
 

Nutball

TreeHouser
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Mt. Juliet, TN
Just what I want to hear, your 35 years of confirmation on this issue. You'd think that would be the first problem/solution in the trouble shoot list in the front of the manual to educate everyone, but we are all too smart to read a chainsaw manual because we might read something we already know.

I had a 015 I used to use, the metal crank case with heatsink fin internal design (structural supports) in the gas tank quickly boiled it. That thing never stayed tuned right, but on the bright side it had a continuously adjustable choke allowing you to always "tune" it just right on the fly.

I wonder if auto tune has vapor lock issues, probably does.
 

Al Smith

Mac Daddy
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Mar 6, 2005
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Northern Ohio
Another thing that might help is to give them a little cool down period before you shut them down .I've seldom had a problem with a hot start with a Stihl,McCullochs yes in hot weather .
You can hold the throttle open and drop start which would be easy on an 015 ,not so easy on an 066 .Do that one on the ground .
 

Nutball

TreeHouser
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Mt. Juliet, TN
Thing about the 015 is you can tune it lean, so you can now create over lean all the way to over rich conditions using the choke for whatever the conditions. If I have to do a full throttle start on a big one, I used to jam my foot in the handle and use big toe to press the trigger, but boots don't fit.
 

Nutball

TreeHouser
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Mt. Juliet, TN
I do the toe thing if I need full throttle, so one hand can hold the saw down while the other pulls. I forget about propping the bar on a log.

Well look at that, my saw is ready for a full throttle start in my picture there
 

SeanKroll

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Oct 13, 2016
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Olympia, WA
If only we could always remember everything we ever learned, at the right time.

Recently, there was some tree trick that I said to myself, I will have to remember that. Should have written it down. Can't even think what it was about!
 

Raj

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Oct 26, 2013
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Brantford, Ontario
Bump.

40C heat has been keeping my 088's from starting. It seems to flood. Seems to have good spark when I test it.
 

Nutball

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Apr 4, 2015
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Mt. Juliet, TN
Tank pressure might force fuel in the engine if that's possible. I had one go lean from vapor lock in the lines today.

And consider the extra low density air from the outside heat + heat from the saw's hot covers. That might cause a rich tune.
 

Burnham

Woods walker
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Mar 7, 2005
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Western Oregon
Super easy to flood when the temps get stooped hot out, ime. In hotter than the hinges of hell conditions, don't choke. Might take a few more pulls to start "cold", but can avoid the flooding.

If the saw is already warm, the only thing I know that has helped me in real hot weather has been to pull the air filter cover and filter off, wipe away any crud you can, then start. If you get her to fire and idle, screw the filter and cover in place and have a go.

Conditions like that, I would let the damn thing idle for inordinate amounts of time versus shut it down and then restart...even go so far as to risk refueling while idling.
 

Al Smith

Mac Daddy
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Northern Ohio
I have one saw,a Husqvarna 2100 that came from some island of the coast of Washington state .I suspect it's been modified to some extent although I've never been inside it to check .At any rate it cuts better than the average of that saw model but it is so easy to flood .On a cold start it's one pull with the choke on and no more else it will flood .I has a large bore Tillotson model HS carb that might have been tweaked .Once it's started for the day it fires up easy,no choke .Believe me that one you don't want to flood,no decomp .
 

Raj

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Brantford, Ontario
Both 088s started no problem this morning. Cooled off to 24C. I think going forward the 088s are going in a bag into the A/C for the ride to the job.
 

Nutball

TreeHouser
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Mt. Juliet, TN
Maybe keep the gas in quart oil bottles in a cooler of ice. Fill up the air conditioned saw with ice cold gas just before you fire them up.

Ice cold bar oil could help cool down the crank case after a run, so the heat doesn't transfer to the gas tank and carb as much.
 

SeanKroll

Treehouser
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Oct 13, 2016
Messages
6,979
Location
Olympia, WA
Both 088s started no problem this morning. Cooled off to 24C. I think going forward the 088s are going in a bag into the A/C for the ride to the job.
A second-hand cooler in the bed, with the cold gas and oil sounds like you're stacking things in your favor.


Any concern over the coil going out?


I wonder about running an oscillating sprinkler over the work, cooling the air, area, and knocking down dust.
A pop-up canopy is great. Has a solar reflector layer in mine. Used it for the largest stump I've ever ground, a massive redwood, splitting wood, neighborhood picnic biz table cover, etc.

https://www.google.com/shopping/product/1047084542340692120?lsf=seller:8638497,store:12041571914110755148&prds=oid:4864544222464604241&q=big+5+sporting+goods+pop+up+canopy&hl=en&ei=WyZBXdacBoHt-gTxq6K4CA&utm_campaign=Elite_Nexus_B_LIA_Desktop-Tablet&utm_source=google&utm_medium=pla&lsft=gclid:CjwKCAjw1f_pBRAEEiwApp0JKJaxR6xsvf2SiTuhsAA65V3COaNiW3oO8abDVmX4Vp_VK5kjcdpfQRoCtkYQAvD_BwE
this has a sidewall, even.

They start at $40 or so. A lightweight tarp can be 'binder-clipped' to the canopy for walls. Probably a carabiner would do, as well.

About two more months of heat.
 
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