Dolmar 5105 weirdness

[clinchscavalry]

Yesterday evening I pulled the 5105 out of my truck tool box, filled it up with gas and bar oil and tried to start it. I couldn't pull the rope at all! So I took the spark plug out and found the reason - the cylinder was full of gas! I dumped out most of the gas and pulled the rope several times to clear out the rest, blew off the spark plug and put it all back together. After just a few pulls (requiring no choke) it started, spit raw gas out the exhaust for a few seconds, smoked a little, then idled and ran just fine. I did some boring cuts with it which required it to run normally at least, and it performed as usual.

What would cause the cylinder to fill up with gas like that?

 

[Ozhoo]

Carb inlet needle is leaking.

How could any cut be BORING?

 

[clinchscavalry]

Carb inlet needle is leaking.

How could any cut be BORING?

Well, it was actually far from boring. I was standing on top of a large pine log about 7 or 8 ft. off the ground, straddling said log and trying to bore a hole straight down to the center so I could insert a stick of explosive in an attempt to split the log which was too big for the sawmill. Lighting the fuse took a while for some reason, and that wasn't boring either

So, could the needle just be stuck momentarily with a possibility of the saw not doing this on a regular basis?

 

[Sepia]

I got this from another site, but this is most likely the part you need to stop the fuel leaking past the inlet valve.

 

[clinchscavalry]

I got this from another site, but this is most likely the part you need to stop the fuel leaking past the inlet valve.
View attachment 579393

Thanks! I ran the saw a couple hours ago, and it seems to be running normally now. Maybe a little Seafoam in the gas might help, but, if not, I'll order that part.

 

[Poleman]

This seems to be some what of an issue with these saws.
Does your saw have foam pad between the diphram and air filter? I ask because I modded a carb on one and cut a small v in the foam so the diaphram could move easier. Now the top of the diphram will fill with chips/partials and cause the needle to stay open and fill the crank with fuel. I repositioned the foam to cover the vent hole again. This is the only 5105 I've had an issue with, the other 2 I didn't cut the v in and are fine. I now know the foam has more junction than to stabilize the air filter. It appears it acts as a filter for the diaphram vent.
Something to check.

 

[clinchscavalry]

This seems to be some what of an issue with these saws.
Does your saw have foam pad between the diphram and air filter? I ask because I modded a carb on one and cut a small v in the foam so the diaphram could move easier. Now the top of the diphram will fill with chips/partials and cause the needle to stay open and fill the crank with fuel. I repositioned the foam to cover the vent hole again. This is the only 5105 I've had an issue with, the other 2 I didn't cut the v in and are fine. I now know the foam has more junction than to stabilize the air filter. It appears it acts as a filter for the diaphram vent.
Something to check.

I'm not sure, but will check sometime this week before using it again this weekend. Thanks for the tip.

 

[Termite]

This seems to be some what of an issue with these saws.
Does your saw have foam pad between the diphram and air filter? I ask because I modded a carb on one and cut a small v in the foam so the diaphram could move easier. Now the top of the diphram will fill with chips/partials and cause the needle to stay open and fill the crank with fuel. I repositioned the foam to cover the vent hole again. This is the only 5105 I've had an issue with, the other 2 I didn't cut the v in and are fine. I now know the foam has more junction than to stabilize the air filter. It appears it acts as a filter for the diaphram vent.
Something to check.

I think every saw I have has the diaphragm open to atmosphere. It does not seem to be a problem.
I bought a 5100 years ago and the dealer cut the foam just as you described.

 

[Poleman]

I didn't think it would be an issue either but it appears it is. I learned the trick from a Dolmar Guru to get the diaphragm to pump better with no restrictions to help feed the little beast, along with some carb mods. With it being on the top of the carb and under the air cleaner I thought it would be rather free is a debris issue collecting on top of the diaphragm but it is, or on my saw it is.

 

[Andyshine77]

Sometimes the needle will stick open when the saws is sitting awhile, but loosen up with a little run time.

 

[fordf150]

Metering lever spring is to soft. Since the tank vent doesn't release fuel vapor/pressure to the atmosphere it builds enough pressure to blow fuel past the needle. Doesn't usually cause a huge issue but riding around in the tool box for any length of time is enough to let an excessive amount of fuel past.