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over heated saws??

Started by boss hoss, August 09, 2008, 09:40:54 PM

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boss hoss

we were clearing 400 yards -prox-of brush today -with 6 guys and 5 saws at 85 degees.
my question is-why is it that when the saw gets hot they won't fire?
i think it may be vapor lock-even though i let the pressure off the gas tank lid.
all advise is appreciated.
IT TAKES TORQUE TO TACKLE TREES-DOES YOUR SAW HAVE A GEARBOX?

timberfaller390

What brand of saw, how big, what kind of and how much oil, do they start after they cool down?
L.M. Reese Co. Land Management Contractors
Stihl MS390
John Deere 50G excavator
John Deere 5103
John Deere 440 ICD dozer

boss hoss

johnsred-3 poolys-and a homie.
40-1/50-1/16-1
what are you thinkin there?
yes-they always start when cold.
IT TAKES TORQUE TO TACKLE TREES-DOES YOUR SAW HAVE A GEARBOX?

mike_van

Saws were telling you 'it's too hot! save this job for fall!'   :D   I was going to say if none would run, maybe it's the gas? But, it looks like you had 3 different mixes.  Unless they all came from the same pump?  Cheap [ha ha] gas or premium?   
I was the smartest 16 year old I ever knew.

Al_Smith

 Sometimes,believe it or not ,the problem is the solid state ignition modual . I had and still have a Mac pm 610 that would do that even in 30 degree weather .

If I shut that thing down after a hot run without letting it cool a little ,you could wait up to a half an hour before the spark came back .Kind of frustrating to say the least .

timberfaller390

Quote from: Al_Smith on August 10, 2008, 07:53:25 AM
Sometimes,believe it or not ,the problem is the solid state ignition modual .
This is kinda what I was thinking
L.M. Reese Co. Land Management Contractors
Stihl MS390
John Deere 50G excavator
John Deere 5103
John Deere 440 ICD dozer

Kevin

It would be interesting to take one of the saws and install a modified muffler on it to allow some of the heat to escape just to see if it makes a difference.
Make sure the saws are clean and free of sawdust which will decrease over heating also.

Al_Smith

 I'm not saying that an overheated coil is definately the cause  but it could be .

In my case of years ago I found that having a little cool down period helped . I might also add that after investigating the problem it seems the cooling fins were a little packed with sawdust  from my neglect .When the thing was running the fan air blast kept the coil cool enough .Once however it got shut down hot the heat had no where to go .

Back in those days it was running tank after tank after full cutting white oak on those old  Macs with 20" bars .It's a wonder we didn't burn them up .We never did though ,they are still operating today . We pulled the muffler screens on them which pepped them up a bit .Made em a little loud though .

Dale Hatfield

I fought with this problem last spring  were were cutting a clear cut .  For a new highway. So no topping. Were we flat mowing trees down and having a great time doing it. But at refuel time  they would refused to restart. We would wait it out a few mins and everything would be fine. But Fuel rep and saw rep told me that it was a change in fuel blends from winter to summer.
Game Of Logging trainer,  College instructor of logging/Tree Care
Chainsaw Carver

boss hoss

advise well taken guys-i knew it had to be something-and now i have several answers thanks to you.
when you have several saws that won't fire after running well on a cold start-something was happening.
you guys rock-thanks.
boss hoss 8)
IT TAKES TORQUE TO TACKLE TREES-DOES YOUR SAW HAVE A GEARBOX?

mike_van

I could see a hot coil on one, maybe two saws - But not all five?  That's why I'd think fuel problem.
I was the smartest 16 year old I ever knew.

Kevin

If it happens again you can pull the plug and see if it's wet with gas and has a spark.
That will tell you if they are flooded, starving for fuel or aren't getting a spark when hot.

olyman

my oly will do the same thing on a warm day---after about 10 minutes of full bore run---and the fins are clean----and itll have pressure in the gas tank----!!!!!  so, im going to investigate further-----

boss hoss

but when you have a supposedly vented gas tank-how does all that pressure build up?
don't know----but would really like to.
IT TAKES TORQUE TO TACKLE TREES-DOES YOUR SAW HAVE A GEARBOX?

beenthere

boss hoss
Is the vent to allow air in, but not allow air out?

If I bring a warm saw in from the cold after sawing, I will get pressure build-up in the fuel tank. Thinking the vent might be to hold pressure in, as when the saw is running.

My thought was the vent was to avoid a vacuum in the tank.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

tyb525

It might be vapor lock-that happens to my saws, and sometimes our lawnmowers too. I think most vents prevent vacuum, but don't always release pressure buildup.
LT10G10, Stihl 038 Magnum, many woodworking tools. Currently a farm service applicator, trying to find time to saw!

Kevin

The air flow into the tank vent is inward.

joe_indi

Had a customer walk in yesterday with 4 saws (all Stihl MS460s) with something similar.
The symptoms were saws are difficult to start when they are hot.When they are running hot they seem to sound as if they are running out of fuel, even though there was fuel in the tanks.
The saws were using the same fuel from the same can.
The cause turned out to be partially blocked pickup bodies and nearly blocked strainers in the carb.
The reason  was narrowed down to bad fuel or container.
Saws ran fine after pickup body replacements and cleaning of the strainers (with fresh fuel from a new container)

Joe

olyman

joe--now thats what i like--a diff view of a problem--ill have to check that on the oly----i be original owner, and never have bad or dirty fuel---buttttttttttttt!!!!!!!

Beweller

My Stihl started to refuse to start when hot.  I took it to the dealer, who allowed (after a week) that there was nothing wrong.  Still didn't start.

Took it back to the dealer, after a week he said it was fixed.  Still (Stihl?) wouldn't start.

I changed the spark plug, it has run fine ever since (two years).
Beweller

boss hoss

we went back to the swamp today to continue the project-same problem.somehow it reminded me of the 2 stroke sled drags that i used to go to.
there they would use 2 stroke  ;) leaf blowers to cool the engine.
don't laugh but i may try this to see if it works.
will advise.
gotta do something-the project is almost over-wood to the burner for the future.
it's been a tough one for this old boy.
heat is good when you need it.
IT TAKES TORQUE TO TACKLE TREES-DOES YOUR SAW HAVE A GEARBOX?

Stihler075

I started carrying a portable air tank and/or small compressor with a blowgun to keep the saw cleaned off and haven't had any overheat probs since;).The only other time I experienced vapor-lock was with a VW Karmann Ghia 20-something years ago :-[.
Stihl 075,mfd 11/1977 and working everyday 31 years later:).
Be careful with advice;wise men don't need it and fools won't heed it.-me and someone else before

Stihlhead Lifer

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