Is my Dolmar 5100S worth the trouble ?

[Doorguru]

Does the carb have that round foam doughnut on the metering diaphragm cover?

Yes. Instead of trying to unglue it, I switched plates with the old carb..

 

[ballisticdoughnut]

Yes. Instead of trying to unglue it, I switched plates with the old carb..

Take a birds eye view picture of the carb with the air filter off, and the bottom of the air filter. I’ve got a pretty good idea as to what’s going on, just need those pictures to confirm.

 

[Doorguru]

Take a birds eye view picture of the carb with the air filter off, and the bottom of the air filter. I’ve got a pretty good idea as to what’s going on, just need those pictures to confirm.

The seller said he just bought the air filter.

It even stalls when installing it open like this, with the top off :

 

[ballisticdoughnut]

Exactly as I suspected. You’ve got two options here. Remove that doughnut or drill a 3/16” hole in the flat portion of the air filter that sits over the doughnut if that makes sense. The vent hole in the metering diaphragm cover is being blocked which is restricting the movement of the metering diaphragm. If you’ll notice, that tube inside the lower half of the air filter is blind. In other words, it’s not a through hole.

 

[Doorguru]

Thanks! That makes a lot of sense.. When I first got and was reading about the 5100, I saw a mention about a hole being needed/not needed in the filter or something like that. How they did away with the hole in newer models or vise versa. I didn't pay much attention to it.

Here is what I read:

"Another change was a air filter change (PN: 181173190). You can cut the little teat with the hole in it(bottom of the AF it goes in the center of the foam circle.) off old AF and put a screw in it. Which is basically what they did. Cut a slot in the foam circle that sits on top of the carb."

The only thing I am confused about.. Dolmar calls it a "seal", so maybe some models came with no foam donut and no hole or the ones that did have the donut had the hole drilled from the factory. (?)

When the seller mentioned that he bought a new filter, he also indicated that he never had it running since the air filter was replaced. Even before he replaced the filter he could not get it running. He even bought a new coil. It was probably just the carb all along.

So in theory, when the saw is running and I cover the foam center hole with my finger, the engine should stall. (?)

I will give a shot tomorrow. I don't want to wake the neighbors.

 

[ballisticdoughnut]

Yes if you cover that hole with your finger the engine will stall out. I had the same problem when I replaced the air filter on my 510.

 

[Doorguru]

It starts and runs now. I cut a notch in the donut. I'm surprised there isn't any info about starting issues because of this. It is mentioned that this should be done, but not the reasoning behind this "modification". I probably wouldn't have figured it out if not for your help and would have tore into it to test the seals. Thanks again !

Apparently the carb had problems too, as It consistently starts now, which it did not before replacing it.

 

[ballisticdoughnut]

Glad

It starts and runs now. I cut a notch in the donut. I'm surprised there isn't any info about starting issues because of this. It is mentioned that this should be done, but not the reasoning behind this "modification". I probably wouldn't have figured it out if not for your help and would have tore into it to test the seals. Thanks again !

Apparently the carb had problems too, as It consistently starts now, which it did not before replacing it.

Glad to hear it.

 

[mudfly]

I’ve been fighting a 5105 with similar issues. Well guess what, same issue. Pulled the air filter off and started first pull.

I had purchased it as a good running saw, but I fought getting it started and leaning out. Thought I had gotten taken. The air filter was on it when I got it, so not sure how it ran well as it was.

Thanks. Now I can maybe use a saw I was about ready to sell for parts/repair.

 

[ballisticdoughnut]

I’ve been fighting a 5105 with similar issues. Well guess what, same issue. Pulled the air filter off and started first pull.

I had purchased it as a good running saw, but I fought getting it started and leaning out. Thought I had gotten taken. The air filter was on it when I got it, so not sure how it ran well as it was.

Thanks. Now I can maybe use a saw I was about ready to sell for parts/repair.

They’re good saws, I’m sure many people have had the same air filter issue. Only reason I know about it is I had the same thing happen on my 510. New OEM filters for the 510, 5100, and 5105 are supposed to come with instructions and a new foam piece to replace that doughnut on the carb. Mine did anyway.

 

[Doorguru]

Just an update. My 5100S usually starts on two or three pulls after using the choke and it is still running strong to this day.