Dolmar 5100 trouble.

[cuttinscott]

I would put money on the chance that the sealer used around the welsh plugs in the zama carb is loose and floating inside the carb. This is a ethanol issue and zama has not cured it yet. It will cause the mixture to change a lot. Get used to it folks TODAY's E10 Fuel is our main issue. I wish we had a alternate carb from another source instead of zama but we don't at this time.


Scott

 

[SawTroll]

I would put money on the chance that the sealer used around the welsh plugs in the zama carb is loose and floating inside the carb. This is a ethanol issue and zama has not cured it yet. It will cause the mixture to change a lot. Get used to it folks TODAY's E10 Fuel is our main issue. I wish we had a alternate carb from another source instead of zama but we don't at this time.


Scott

I once hears that Zama carbs were just copies of Walbro ones, with the ventury adjusted up to the closest mm (as opposed to 1/64") - is that totally wrong???????

 

[SwampBuck]

I would put money on the chance that the sealer used around the welsh plugs in the zama carb is loose and floating inside the carb. This is a ethanol issue and zama has not cured it yet. It will cause the mixture to change a lot. Get used to it folks TODAY's E10 Fuel is our main issue. I wish we had a alternate carb from another source instead of zama but we don't at this time.


Scott

Good thinking Scott. I have an MS180 with a ZAMA Carb that showed similar behavior. After disassembling the carb numerous times, I finally applied a little clear nail polish over both of the welch plugs. Problem solved, and inexpensively. It's definitely worth a shot.

 

[Andyshine77]

Well I set a piece of oak on the log stand, setup the camera, started the saw up, and without any adjustment it ran almost perfectly.:dunno: Hopefully it won't act up again, I'm keeping my fingers crossed.

Andy.

Here's the video anyway.

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[DMShaver]

Good thinking Scott. I have an MS180 with a ZAMA Carb that showed similar behavior. After disassembling the carb numerous times, I finally applied a little clear nail polish over both of the welch plugs. Problem solved, and inexpensively. It's definitely worth a shot.

I always use nail polish over welch plugs after reinstalling them. It insures that they seal completely and the ethanol should not affect it.

 

[stckciv]

I always use nail polish over welch plugs after reinstalling them. It insures that they seal completely and the ethanol should not affect it.

Do you use the same color as you do when you paint your nails?



j/k I do the same. Nail polish works great on carbs. and have yet to have it fail due to gasoline.

 

[RiverRat2]

Very well written detailed how-to Shaver!

Yeah Did ya rep him?????


I did!!!!!!!

 

[Lignum]

Rep coming his way for that explanation.



Andy, are you having any better luck with it?

 

[Lakeside53]

. (The saws are tuned in Germany on Aspen fuel, and when using US fuel, they need to run a bit richer.) .

Are you sure?

I almost certain that saws for the USA aretested using an EPA approved "typical" fuel... If not, the emission test is invalid. Apsen isn't on the EPA radar.

Stihl uses a custom EPA approved E10 mix so saws do not run lean(er) when using street mix.

 

[SawTroll]

Great explanation DMShaver.

Rep.

Yes, I hit hom hard - two new golden ones!

 

[Poley4]

Yeah Did ya rep him?????


I did!!!!!!!

Absolutely!

 

[DMShaver]

Are you sure?

I almost certain that saws for the USA aretested using an EPA approved "typical" fuel... If not, the emission test is invalid. Apsen isn't on the EPA radar.

Stihl uses a custom EPA approved E10 mix so saws do not run lean(er) when using street mix.

I'm assuming that they are. When I open the fuel cap on a new Dolmar, it has the smell of the Aspen fuel. The weak white gas smell. I will make a phone call and find out for sure though.

 

[RedFir Down]

I realize this thread is over 12 years old, sorry to dig it up for those that care.
I have a 5100 I'm getting going and can't get it tuned right. It starts and idles great but once you go WOT and check it with a tach is where my concern begins... the saw will go from 12,300 to 14,400 with the slightest H screw adjustment, there is no in between.
The saw is low hour. Compression is good, I pressure / vac tested and found a small leak between the intake boot and the cylinder so I pull the cylinder and fixed that. Now it holds 8 psi steady for 5+ minutes. The fuel line, filter are new as well as an OEM carb kit.
Andre did you ever sort yours out? @Andyshine77

 

[Andyshine77]

Wow blast from the past. These saws have a revlimiter so when that kicks in it will cause the RPM to jump all over the place, if the saw runs fine otherwise, I bet that's what is going on. Just tune it a little under that and see if rpm more or less stabilize. Does the intake boot have a sealing ring where it mates with the carb? That normally just affects the saws idling characteristics.

 

[Jeff Lary]

I have no idea if " DMSHAVER" is still a member here or not but I thought that the carb adjustment write up was great, thank you! I have a 5105 I don't know if the 5100 and the 5105 share the same tune characteristic's or not but I saved his write up just in case . I can tell you my saw adjusts kind of the same way,.. I would say that 1/16 turn on the L or H will make tremendous changes in the saw. I have never seen anything so touchy.

 

[Jeff Lary]

Wow blast from the past. These saws have a revlimiter so when that kicks in it will cause the RPM to jump all over the place, if the saw runs fine otherwise, I bet that's what is going on. Just tune it a little under that and see if rpm more or less stabilize. Does the intake boot have a sealing ring where it mates with the carb? That normally just affects the saws idling characteristics.

Yes I have the 5105bought new a couple years ago (2018 or 2019 maybe) and when the limited coil begins it sounds funky like it is breaking up. I think someone said the coil shuts the electricity off thousands of times a second?

 

[RedFir Down]

Wow blast from the past. These saws have a revlimiter so when that kicks in it will cause the RPM to jump all over the place, if the saw runs fine otherwise, I bet that's what is going on. Just tune it a little under that and see if rpm more or less stabilize. Does the intake boot have a sealing ring where it mates with the carb? That normally just affects the saws idling characteristics.

I don't think I'm hitting the rev limiter because I get consistent numbers from my tack (stihl edt7), when I hit the limiter my tack goes crazy and reads random limited signal.
Like I said the saw will go from 12,300 to 14,400 with the slightest turn of the H screw.
I would like to tune the saw in the 13,500 area.
I have the metal intake ring and eliminated the goofy air compensator on the air filter.

 

[Andyshine77]

Well sounds like you've got the saw well sorted out otherwise. Only thing I can think of is a bad seat on the carb. I also had a 7900 that at had a leaking welsh plug that caused erratic tuning. Could also try swapping the coil, the early ones were known to fail, but because the saws is stable unless you touch the carb, I doubt it's the coil.

 

[Flydaho]

Great info on this thread! If you problem shows up again, I suggest replacing the carb with a Zama C1Q DM13B (can be had on ebay for $45 +/-). It seems to have fixed a lot of the carb issues on this particular saw.