5100 idle?

[Marco]

Has the thaught of a slightly restricted fuel supply come up? You are running the saw at WOT and it maybe starving for fuel and racing at idle until the fuel supply can "catch up". I thaught air leak too, but then they usually never slow down. Just an idea because it was mentioned that the jet screws had to be backed out quite abit. Fuel tank vent maybe plugged.

 

[jokers]

Tim and I met up this afternoon and ran saws for a while. The 5100 was still acting up. After 5 minutes of steady running, it would hardly idle at all. The more you used it, the longer it would hang at 3-4K rpm before dropping to idle. The jet settings were much further out than I would have expected. 2 turns on the low speed jet and 2.5 on the main jet. The richer we went, the better it idled but throttle response suffered. Leaning it out less than 2 turns on the main jet and the saw would continue racing when the throttle was released. Leaning out the low end jet made everything worse as well.

I just got done pulling the carb for a quick basic check, blew out the jet orifices and double checked the metering valve height. Everything looked normal and I reassembled. Fired it up and nothing has changed. It's as if the carb is too dam small for the saw. All the linkage movement is smooth and unobstructed (repeating this for the people who want to suggest a sticky linkage problem again).

So as it stands now, we can choose between a racing idle or crappy throttle response. And the overall performance of the saw is pitiful compared to 3 different 346's from 2 builders. I'm pretty much convinced there is some blockage in an internal orifice somewhere. There is little difference between 2.5 turns and 4 turns on the main jet. About 5 turns and the saw dies instantly.

Perhaps the mods recently done to this saw have made it more thirsty and necessitated enlargement of a certain carb orifice that has yet to be done.

Russ

 

[stihltech]

hi anxiety

you are too lean on the low end. It may be a fuel issue, but I am betting on a VACUUM leak. A seal with the garter spring off. The onlt way to know is a pressure and vacuum test. Even if it checks out good, you now know that the bottom end is nice and tight.
Just how much porting was done on the cylinder.



Ask Ed.

 

[timistall]

I hope the problem turns out to be something simple. It's turned out to be an expensive new project(should of bought a stock 361) Maybe we should video a 5100 fed thru a chipper

 

[trimmmed]

Gotta be aggravating, I'm betting the shipping is adding up on that saw.

There was a gift horse siting back on post 15 . Nice offer by cuttinscot.

http://www.arboristsite.com/showpost.php?p=375581&postcount=15

 

[skwerl]

I found the problem today. Went and bought some aerosol carb cleaner. Fired up the saw and had it running at an idle. When I sprayed carb cleaner around the throttle shaft the saw would stall. So it is an air leak. Explains why the low end jet is 2-2.5 turns out in order to stay running.

Dave Neiger (who modded the saw) has been on the phone with me constantly through all this. I'm certainly appreciative of his time and advice. He said he would send another carb for it. I'm also glad I've been able to help Tim with his saw.

Looking forward to getting a good carb on this saw and running it next to the three 346's we have laying around.

 

[timistall]

Gotta be aggravating, I'm betting the shipping is adding up on that saw.

There was a gift horse siting back on post 15 . Nice offer by cuttinscot.

http://www.arboristsite.com/showpost.php?p=375581&postcount=15

Cuttinscott's offer was more than nice. The reason I didn't take it was the saw wasn't stock. 166, cuttinscott, and Dolmar Tech Mgr have all been helpful offering service. We still have high hopes for the 5100.

 

[McC]

My 5100 is completly stock. I cut a load of firewood today. The fast idle was almost undetectable. I richened the idle mixture 1/8 turn and it was completly gone. My saw is not going anywhere near a chipper.
Scott

 

[Dolmar_Tech_Mgr]

Glad the issue was resolved. Was there anything done to the carburetor or was it stock. If it is stock and no mods done to it I would like to get it back to send to the factory.

 

[skwerl]

I'm not sure if Big Dave modified the carb other than disabling the EPA adjustment stops. I'm waiting to hear back from him, not sure if he's talked to Tim today or not. The saw is sitting in my shop for the time being until we get the carb. Tim can send the old one wherever Dave wants.

 

[94TahoeLT]

I had the same issue with my Dolmar Ms-260C string trimmer.
running it at WOT then let off and it took about 4-5 seconds to go back to idle.
but it only took me a few minutes to figure it out. as the carb is exposed more.
The end of the cable was sticking on the butterfly pulley before it would close all the way.
I blew it off push it back in with my finger sprayed some K&N air filter oil on it as that is all I had with me.
It hasn't acted up since, that was about a month ago.

 

[pallis]

I hunted for this thread a while back. The first real day on the job with my 5100 it got to where it wouldn't idle down. When I got the saw home, I discovered the carb screws were loose, as was suggested to me by "166." I also discovered that the fuel line had a bit of an air leak at the carb. I ended up pulling the carb, checking the purge line, cleaning the carb and fixing the air leak, and the saw has run great until a couple of days ago. It raced at idle again. Rather than fool with it, I set it aside and got my 372 out. Once it warmed up, it did the same thing. I retuned it, and it ran fine, so I retuned the 5100, and it ran fine. I have no idea what happened. The last time I ran both saws they were at the same altitude, about 8000 feet. My 7900 that my son was using ran fine, same fuel, last tuned at the same altitude. ...That was the good part of the day. My son had sharpened the chains with the new $29.00 grinder from Harbor Freight. They looked good, but didn't cut worth a crap. I had to sit on a steep slope and file the chains, holding them far enough away to see without my reading glasses. All that done, we finally got a good load of firewood. I'm still trying to figure out what made the saws speed up at idle. ...I should add that the 5100 isn't exactly out of the box stock, but I have no idea what has been done to it, and as long as it cuts as well as it does, I'm not going to pull it apart to look.

 

[Chainsaw Master]

I found the problem today. Went and bought some aerosol carb cleaner. Fired up the saw and had it running at an idle. When I sprayed carb cleaner around the throttle shaft the saw would stall. So it is an air leak. Explains why the low end jet is 2-2.5 turns out in order to stay running.

Dave Neiger (who modded the saw) has been on the phone with me constantly through all this. I'm certainly appreciative of his time and advice. He said he would send another carb for it. I'm also glad I've been able to help Tim with his saw.

Looking forward to getting a good carb on this saw and running it next to the three 346's we have laying around.

My 5100 started this high idle crap today.......is this the most likely problem? It also seems to be over reving.......almost to high.....Its still under warrenty should I take it back or look fix it myself??

 

[begleytree]

under warranty=take it in
-Ralph

 

[166]

My 5100 started this high idle crap today.......is this the most likely problem? It also seems to be over reving.......almost to high.....Its still under warrenty should I take it back or look fix it myself??

Take a T27 Torx wrench & check the tightness of the 2 bolts on the carb. You will probably get 1/2 - 3/4 of a turn on each. That should take care of your problem.

Steve

 

[Chainsaw Master]

Take a T27 Torx wrench & check the tightness of the 2 bolts on the carb. You will probably get 1/2 - 3/4 of a turn on each. That should take care of your problem.

Steve

I tightned the bolts, both took about a 1/2 turn, started it up, it sounded good, untill it got hot, then started the high reving again. I turned on the high jet , what little the limiter caps would let me, and it made no difference at all. It seems to be sucking air some where..........
thanks for answering

 

[166]

I tightned the bolts, both took about a 1/2 turn, started it up, it sounded good, untill it got hot, then started the high reving again. I turned on the high jet , what little the limiter caps would let me, and it made no difference at all. It seems to be sucking air some where..........
thanks for answering

Spray some carburetor cleaner around the throttle shaft to test for an air leak. I have not seen this personally on a 5100 but I have seen a couple on 7900's. I think this was the problem with timistall's 5100.

Did you buy this saw from a local dealer or through this site?

Steve

 

[Mikey von]

I hope my new saw does not have this problem! Good luck getting it fixed. Let us know how it goes.

Michael

 

[sugarbush]

I tightned the bolts, both took about a 1/2 turn, started it up, it sounded good, untill it got hot, then started the high reving again. I turned on the high jet , what little the limiter caps would let me, and it made no difference at all. It seems to be sucking air some where..........
thanks for answering

Are you stihl running that 91 bar? if so did you have it checked with a tack?

 

[Chainsaw Master]

Are you stihl running that 91 bar? if so did you have it checked with a tack?

Yup still running the 91 bar, they set it up at the dealer, so I figured they put a tack on it. .....Sprayed some carburetor cleaner around the throttle shaft while idling, and it stalled, 3 different times, so I'm gonna take it back to the shop. Its a 40 mi. drive tho....