Dolmar 5100 runs too fast

[Cazimere]

I was just out cutting with my 5100 and after a few cuts it would not idle down. The engine just wanted to keep racing.
Even set the switch to stop and it kept racing till i put the chain against a log to stop it. Any ideas ?

 

[smokinj]

Sounds like the saw is running very lean. There a lot of people running these 5100's I will let one of them chime in.

 

[wkpoor]

You have 2 problems there. 1st the stop switch grounds the coil and that must not be happening if it runs when you push down on the sw.
As for not idling down it could be, improper tune ie running lean on low side. Air leak mostly at cylinder base but could be crank seals too. Or sometimes, this just happened to my neighbors saw, a plugged vent hole on the carb that vents the needle control diaphragm. There is 2 different configurations for that vent hole. One is the air filter as small hole in the bottom that sits right over a piece of foam thats over the hole. Take a blow gun and make sure that is all clear and clean. The other is the filter has no hole and the filter is removed. 5100s are real sensitive about plugged air filters that in turn effect that vent hole. Thats why the new filter housings did away with the hole.

 

[wkpoor]

Many saw problems can be traced back to house keeping. Close the choke and give it a good blowing out daily, that can solve alot of problems.

 

[LLigetfa]

The saw was running too lean. Most likely you need to clean the carb.

As for it not shutting off, given the lean condition, it was just dieseling. No need to tear apart the switch.

 

[Cazimere]

Turns out my Dolmar did not like the same gas that all my other saws run fine on, which is regular gas with ethanol mixed at 40/1.
I just mixed a batch of 93 octane E-Free gas at 50/1 and it runs just fine.
Thanks for the ideas guys.

 

[oldspark]

Turns out my Dolmar did not like the same gas that all my other saws run fine on, which is regular gas with ethanol mixed at 40/1.
I just mixed a batch of 93 octane E-Free gas at 50/1 and it runs just fine.
Thanks for the ideas guys.

That's interesting, I hate the E stuff for chainsaws and have been running the 91 E free gas. Do you spose the saw is way to lean for the E gas?

 

[Cazimere]

Don't know. I got it new 8 years ago. It's still on the factory settings.

 

[othelloears]

Just saaw this post. i run a 5100s and had the same problem when I first got it. Would run up for a couple of seconds.

There was a recall on earlier models to fix a air leak around the carb if I remember. Dolmar will give you a recall kit. It mainly deals with tightening the screws to the carb I think (Its been 2 years)

 

[wkpoor]

I have found the screws loose too. And the early ones had a problem with the carb boot. But if there isn't a cylinder leak I would look at the little tiny filter between the filter and carb.

 

[oldspark]

He says it runs fine on the non e-gas, I took him at his word.

 

[wkpoor]

He says it runs fine on the non e-gas, I took him at his word.

He'll be back. Unless it was just a stroke of luck putting in a new tank of gas I don't believe fuel was the problem. Might have been the reason if it was stored with ethanol but not the problem otherwise. I'm sure I could dump in ethanol in my saws (not pp saws) but stock and they would run fine. Also I've owned alot of 5100s (4) and I know they run fine on any pump gas.

 

[DiscoInferno]

My "new" used 6401 did exactly the same thing, turned out the wizards at Home Depot hadn't noticed the spark plug was halfway unscrewed. Instead of fixing that, they had monkeyed with the carb and jacked the idle sky high. Thankfully I caught it early.

 

[oldspark]

Ok, it sounded like too simple a fix. :lol:

 

[blades]

can also be caused by air leak through crankshaft bearings

 

[wkpoor]

can also be caused by air leak through crankshaft bearings

Absolutely can be. Much harder to test for. Bar side is easier to do when running but flywheel side is all but impossible. So you would be down to a crank case pressure test with block off plates. Unless it is a real high time saw I would think its most likely something else when this comes up.

 

[Cazimere]

Just to be clear, the 40/1 mix with ethanol was not "bad" gas. It was less than 30 days old and i never let gas sit in a saw if i'm not going to be using it for more than a week or two.
Saw is still running fine with the 50/1 E-free mix, but i will check those carb screws this weekend before i start cutting just to be safe. Thanks : )

 

[Battenkiller]

Just to be clear, the 40/1 mix with ethanol was not "bad" gas. It was less than 30 days old and i never let gas sit in a saw if i'm not going to be using it for more than a week or two.
Saw is still running fine with the 50/1 E-free mix, but i will check those carb screws this weekend before i start cutting just to be safe. Thanks : )

I have a friend who is a Dolmar sponsored chainsaw carver. He insists on running his saws at 40:1 and has nothing but problems. I took four of his 420s to the local repair shop. All had signs of overheating and three had bad coils caused by the excess heat. He got all four saws back with the recommendation that he keep his saws cleaner and to run 50:1 synthetic as the saw is designed for. He is the stubbornest dude I know and is always right about everything, so I'm sure they will be back in the shop before too long. He never tunes his saws and thinks 40:1 and never running your tank dry are the answers to all saw problems.

Never noticed one of his saws dieseling, though. I'd look a little deeper into things if that happened to one of my saws.

 

[wkpoor]

Just to be clear, the 40/1 mix with ethanol was not "bad" gas. It was less than 30 days old and i never let gas sit in a saw if i'm not going to be using it for more than a week or two.
Saw is still running fine with the 50/1 E-free mix, but i will check those carb screws this weekend before i start cutting just to be safe. Thanks : )

I have a friend who is a Dolmar sponsored chainsaw carver. He insists on running his saws at 40:1 and has nothing but problems. I took four of his 420s to the local repair shop. All had signs of overheating and three had bad coils caused by the excess heat. He got all four saws back with the recommendation that he keep his saws cleaner and to run 50:1 synthetic as the saw is designed for. He is the stubbornest dude I know and is always right about everything, so I'm sure they will be back in the shop before too long. He never tunes his saws and thinks 40:1 and never running your tank dry are the answers to all saw problems.

Never noticed one of his saws dieseling, though. I'd look a little deeper into things if that happened to one of my saws.

I respectfully dissagree that a richer oil mix is the source of a hot running saw. Lean air/fuel ratio will cause a hot running saw. I would like you to take that over to racesaws or arboristsite and see what they say. I have run 40:1 for yrs with no trouble.
First off do you know for sure his mix was really 40:1 and second how are they tuned?

 

[Cazimere]

Just to be clear, the 40/1 mix with ethanol was not "bad" gas. It was less than 30 days old and i never let gas sit in a saw if i'm not going to be using it for more than a week or two.
Saw is still running fine with the 50/1 E-free mix, but i will check those carb screws this weekend before i start cutting just to be safe. Thanks : )

I have a friend who is a Dolmar sponsored chainsaw carver. He insists on running his saws at 40:1 and has nothing but problems. I took four of his 420s to the local repair shop. All had signs of overheating and three had bad coils caused by the excess heat. He got all four saws back with the recommendation that he keep his saws cleaner and to run 50:1 synthetic as the saw is designed for. He is the stubbornest dude I know and is always right about everything, so I'm sure they will be back in the shop before too long. He never tunes his saws and thinks 40:1 and never running your tank dry are the answers to all saw problems.

Never noticed one of his saws dieseling, though. I'd look a little deeper into things if that happened to one of my saws.

I respectfully dissagree that a richer oil mix is the source of a hot running saw. Lean air/fuel ratio will cause a hot running saw. I would like you to take that over to racesaws or arboristsite and see what they say. I have run 40:1 for yrs with no trouble.
First off do you know for sure his mix was really 40:1 and second how are they tuned?

Already did. Read post #6.
(broken link removed)

 

[wkpoor]

Just to be clear, the 40/1 mix with ethanol was not "bad" gas. It was less than 30 days old and i never let gas sit in a saw if i'm not going to be using it for more than a week or two.
Saw is still running fine with the 50/1 E-free mix, but i will check those carb screws this weekend before i start cutting just to be safe. Thanks : )

I have a friend who is a Dolmar sponsored chainsaw carver. He insists on running his saws at 40:1 and has nothing but problems. I took four of his 420s to the local repair shop. All had signs of overheating and three had bad coils caused by the excess heat. He got all four saws back with the recommendation that he keep his saws cleaner and to run 50:1 synthetic as the saw is designed for. He is the stubbornest dude I know and is always right about everything, so I'm sure they will be back in the shop before too long. He never tunes his saws and thinks 40:1 and never running your tank dry are the answers to all saw problems.

Never noticed one of his saws dieseling, though. I'd look a little deeper into things if that happened to one of my saws.

I respectfully dissagree that a richer oil mix is the source of a hot running saw. Lean air/fuel ratio will cause a hot running saw. I would like you to take that over to racesaws or arboristsite and see what they say. I have run 40:1 for yrs with no trouble.
First off do you know for sure his mix was really 40:1 and second how are they tuned?

Already did. Read post #6.
(broken link removed)

Good for you Andyshine77 is a friend of mine and has been to all of my GTGs and knows his saws. We have talked 5100s for yrs. I see he was recommending higher octane gas( and I keep telling people the AvGas will lower your temps, but nobody will listen to me on here). One of my saws that has a bunch of time on it, my neighbor has it, didn't act up till it was run with 87 pump gas. If you have any trouble with that 5100 I would stay on the arboristsite and stick with Andy's recommendations or I'll steer you straight.

 

[oldspark]

Hey wkpoor I will listen to ya, I switched from non-E 87 to non-E91 but did not notice any difference but I did not want to run the new 361 on the 87.