Dolmar 5100s problem

Well guys I had a strange problem with the 5100S I bought a little over a year ago.

It worked great last fall, This fall I had asked my dealer to order the metal ring insert which is intended to help with sealing problems between the carb and the boot as I checked mine and it didn't have one. A while later I had tried the saw with fresh 91 octane fuel and fresh stihl two strike oil (40:1) and it appeared to run lean at WOT in fact it would almost die right out. I decide to wait for the metal insert ring as I figured that may be the problem.

Well a couple months later still no metal insert ring at the dealer (he received only a couple and they went to other saws in the shop and no rings had been received since). I was getting impatient so I decided to order one from Cuttinscott who was able to send me one immediately (thanks Scott)
After installing the insert, there was no improvement in the operation. The saw will start and idle normally and accelerate quickly but after a few seconds of WOT, it seems to go lean in that it starts to rev faster for a second or two then drops off. (Similiar to running out of fuel) If I keep the throttle open it will often stall. If I baby the throttle the instant it begins to rev higher, I can keep it runnning at about 2/3rd top speed.


Things I tried:
Tried another plug (plug had very light brown colour,almost too light) the fuel mixture has been run in another of my saws so I am confident it is OK, I removed the plastic limiters on the mixture screws and adjusted the HS richer, checked the fuel filter (looked clean and could blow air through), air filter is clean checked the fuel hose for leaks/splits/cracks in the carb area as well as in the tank, put a tye wrap on the fuel line which connects to the carb as it didn't seem to be really tight, removed and reinstalled the carb a few times to ensure everything is mating properly and the mounting screws are tight, removed the top of the carb (metering area) and was able to blow through the high speed orifice with a rubber tube sealed over the hole with my mouth and there didn't seem to be any restrictions, the bar and chain is almost like new and lubed properly and rotates by hand very easily,
as well I tried loosening the chain etc., removed and cleaned the fuel tank air vent filter and I could blow through the vent by mouth with a rubber tube sealed over the vent hole, checked compression more than 180psi. I was stumped (no pum intended) To me it really seemed like a (lack of) fuel problem.

Now for the really odd part. As I was trying to cut a limb, I decided to cut from underneath, (using the top of the bar) and low and behold the problem went away. I immediately began cutting from the top (using the bottom of the bar) and the problem came back, as well when not even in the cut the problem persisted. Tried cutting underneath, problem went away for the duration of the cut.

I took the saw home, did some checks and found what I believe was the problem.

What do you think is my problem??????

Well when you're cutting down (using the bottom of the bar) you're pushing down on the handle. When you're going up, you're pulling up on the handle. Maybe a tight hose or seal somewhere that was coming apart when pushing down but not when cutting up?

+1... check your boot... etc.

I'd just do a quick pressure test. Is it under warranty? if so, make your dealer do it..

Yes I've seen a similar thing on a Homelite 360/330 can't remember exactly, but with broken A/V mounts it allowed the handle to lift too far, popping the seal on the carb boot.

Sure sounds like a crack in the boot or not installed right. Or a pinched or cracked fuel line. Steve

You are all pretty close. I mounted the bar in a vise and noted the movement (due to antivibration mounting) between the fuel tank
assembly and the carb housing when exerting a force similar to when cutting using the top of the bar.

I got in with a pen light and noticed the fuel line was being pinched in this area. When I disassembled, I noticed that the fuel line appears to be
extra long in this area. It is a special line in that it has a sealing gromet/mount at the area where the line enters the tank, plus two more gromets
towards the carb. The one gromet closest to the carb would go on the inside of the housing where the carb is located (to block out any dirt etc.)
but I can't seem to figure out the function of the other (middle) gromet or if it is intended to mount somewhere or keep the line from moving. As I mentioned
the line seems to be longer than necessary and after re-assembling, I noticed it tends to kink due to the excessive length.

Here is a diagram of the line. See page 2, item 12 which is the fuel line.
http://www.mwe.net/dolmar_pdf/995700048.pdf

Sorry I don't have a digital camera at the moment, but the line seems to kink along the half closest to the tank gromet.

Has anyone else experienced this problem with the Dolmars?

Would anyone have any photos of their saw showing this area or have any idea of the proper routing/mounting of the fuel line between the tank and
the carb housing?

thanks

Is the line twisted or just kinked? Haven't seen any do this. I have a new fuel line in stock if you need one.

Steve

should have bought a Husqvarna xp

Every manufacturer make some mistakes now and then, I believe - mostly on mondays. On the Husky made saws, the serial number tell you about when in the week they are made - avoid the xxxx000xx ones.... :taped:

LOL sawtroll. I thought it was Fridays. I had a 359 E-tech in a while ago. Owner's complaint: It would start OK cold, but was real hard to start warm. He took it back to the dealer he bought it from, they told him that's how those saw are made. Finally it got so bad, it would shut off after 15 or so minutes of use and wouldn't restart for a while. It sure seemed like gas tank vacuum - tried a new fuel tank vent, made no difference. So I decided to rebuild the carburetor, and discovered the problem. The spring underneath the metering lever was doubled over. Put a new spring in, and the saw ran great. Started great. I believe that spring was like that since new. The owner was sure it must've been assembled on a friday afternoon. His comment? Those Swedes couldn't wait for their Friday night beer...
Anyways I'm sure those carbs are assembled elsewhere - don't blame the Swedes

Thanks 166 for the photos. They both look the same as to what I have. Looking at the bottom photo, the bottom half of the fuel line on mine seems to kink when assembled. When you put yours back together you will notice that there is much more fuel line than needed in that space and my line bends around sharply and appears to kink. I am able to see it when I look in the crack between the tank and carb housing from the rear of the saw towards the bar side. I can also see the kink, it if I flip the saw upside down and viewing near the chain oil adjusting screw and looking on an angle towards the hose. (You need a small pen light) If you look at your bottom photo, near the bottom of the hose in behind it there is a lip jutting out. That is where mine was originally being pinched.

I may just give it a try, perhaps the kink isn't as bad as it looks. I'll let you know how things go.

Fuel lines often look "kinked" but work well. It's why they are molded and not ordinary hose.


If you want to prove if this is the problem connect a 3 foot hose from a coffee can or whatever, and run the saw with the can hung high.

Lakeside53 said:

Fuel lines often look "kinked" but work well. It's why they are molded and not ordinary hose.

If you want to prove if this is the problem connect a 3 foot hose from a coffee can or whatever, and run the saw with the can hung high.

Click to expand...

A Dolmar IV? Wow... chainsaw triage.

bearings

I had a brother in-law that had a lot of problems with his 5100. It ended up being crank bearings went bad. I know its not a normal problem but they do go bad.

ummmmmm

441_Stihl said:

should have bought a Husqvarna xp

Click to expand...

What's wrong with 441_Stihl telling someone they shoulda bought a husky???

hehehehehe

eh?

I got a chance to run the saw today and figured I would update you guys on the results. As Lakeside suggested, it seems the perceived kink does not affect the operation of the saw on WOT.

So to recap, the fuel line was found to be pinched. (when undercutting with the saw, the slight movement between the fuel tank and the carb housing assembly was enough to relieve the pinch and allow the saw to operate normally under WOT.) After resolving the pinch problem I noticed the line appeared to be somewhat kinked, but apparently not enough to cause any further problems.

Needless to say I am once again a happy camper and would like to thank everyone for their help!!