Dolmar 5100 trouble.

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Andyshine77

Andyshine77

Tree Freak
. AS Supporting Member.
Joined
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Location
Cincinnati, OH
As some of you know Ohio was hit by Ike pretty hard on the 14th, we had wind gusts up to 80 mph here in Cincinnati. I had 6 trees come down in my yard, and 17 in my neighbors. I maintain my neighbors property, as he's in his 80's. Needles to say I've been running a saw everyday after work since the 14th.

Today I had a large Ash top to deal with, so I decided to try and use my 5100, and like always it was a no go. Every time I pick up the thing I think to myself, why do I even bother. Let me give everyone a little background on my experience with the loved 5100.

In October of 06 I went to a local Dolmar dealer and bought a shinny new 5100. The minute I got home I fueled it up and went out to the wood pile to see what all the hype was about. To my disappointment it had almost no power and would not idle at all, and adjusting the carb did nothing. So off to the dealer I went. Dealer tested the saw and said it had a bad coil, he handed me a new saw and I headed home. When I got home I tested the saw out and it ran ok not great but ok. A week later I noticed it would rev up if you held the saw on it's side, then it would almost stall when u flipped it upright. After trying to fix the saw myself I gave up and sent it to the cutting edge. Scott and Steve determined the cause of problem, a small air leak between the carb and carb boot, the metal sealing ring fixed that problem. Sadly I noticed a new problem, It simply will not hold a tune. If you start the saw and set the L screw the saw will idle fine for as long as you want it to, but if you go WOT it will idle crazy fast, and if you re adjust, it will do the opposite. I've tried my best to fix this thing, I've checked everything, vacuum tested the carb, the seals are good, fuel lines, fuel filter, everything.

Here's a video of me trying to tune the carb. At this point I'm done wasting my time with this saw.

:cheers: Andy.

Here is the video.
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If I'm understanding you, you're saying when you set the L screw, it will idle fine but when you go to WOT it will not return to a correct idle but wants to rev or idle extremely high?

If so.....Is it possible the throttle cable is sticking/hanging up on it? Have you checked that?
 
I'm probably missing something here, but on my 5100, you set the idle with the S screw. The H screw is for setting top speed and the L screw is for setting acceleration.
Are you sure your not adjusting the wrong screw Andy ?
 
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Ok, I didn't watch the video before I posted the first time. It seems like it drops back down to the proper idle but then speeds up again. That may rule out the sticking cable.

This may sound crazy but is your chain tight? It looks like it's creeping, even when idled down. It seems that by keeping my chain good and tight on my 5100 it doesn't allow the crapola Zama carb to act possessed at idle. Almost like, if you give it an inch it wants a mile. The tight chain seems to keep/hold back the carb from wanting to do that little burst, after it throttles down.

Mine did some strange stuff like that and also wanted to not hit wot till about 1/2 way through the first cut. I tightened the chain up and leaned both the L & H screw slightly and she has run mint ever since.
 
I have the same exact problem with 5 new dolmar saws at my shop!!!!
The models are 460 X2 5100 X1 510 X2
Tech cannot even find the problem!!!!
Mabie we will get some answers now that I see more people having the same problems.:clap:
 
Well no problems of that sort here on the Dolmars, did have one Shindaiwa that had a similar problem. It was impossible to adjust the idle speed. After revving, it would drop waaay down, then speed up really fast. When adjusted to proper idle speed, it would shut right off when coming off a rev. When adjusted so it wouldn't shut off, it would return to a very fast idle. Replacing the carb solved that one...
 
Gota be an air leak somewhere... Or a bad carb.

Would a case seal cause that?
 
Tech had me run a new saw to test the carb, after the carb was run in with the saw, I would remove it and put it on the faulty saw but the curplit still did not run correctily. I have pressure and vacuum tested all of these saws and installed that ring between the boot and carb which causes them to run worse:cry: :cry:
 
The carb. on a 5100 can be finicky at times. I've had many that are difficult to get into adjustment. When adjusting the carb on these saws, the first thing to do is remove the limiter caps, screw both screws in until they seat lightly, and back both out 1 1/4 turns. Many times you can't do a complete adjustment with the factory settings. (The saws are tuned in Germany on Aspen fuel, and when using US fuel, they need to run a bit richer.) Turn the idle adjustment screw (S) in 2-3 turns and start the saw. Back out the S screw until the RPM is approx. 3200. Turn the L screw in until the RPM's start to rise, and continue turning until you hear them start to die off. Turn the L screw back out a touch. Readjust the S screw to obtain an RPM of 2900 to 3100. Pull the throttle and the saw should jump to life. If it hesitates, the mixture is too lean, back the L screw back out a touch more, and repeat the process until the saw does not hesitate any more. Realize that on this particular carb., adjustments as little as 1/16 of a turn on the low side can make a huge difference. Now do a "dump test". Allow the saw to sit in the normal position for 30 seconds. Abruptly tip the nose of the bar down and listen for a change in RPM. If the saw stalls, the L screw is out to far and needs to be adjusted back in a touch. Repeat the process until a "dump test" can be performed without the saw stalling. Recheck the acceleration, it should still be quick. If not, back the L screw back out a touch etc., etc., etc. It may take a few times back and forth, but if the carb. is functioning properly it will come into adjustment. Now run the saw at top-no-load (TNL) RPM. (Note: the chain should be tightened to the point in which is just starts to droop of the bar, and should spin freely. An over tightened chain will not yield an accurate adjustment.) Pull the throttle and observe the TNL RPM. Given that this saw has an electronic rev limiter, it will not exceed 14,500-14,700 RPM. Back the H screw out until you see the RPM's start to drop (richening the mixture). I have found that these saws perform extremely well with the TNL RPM right around 14,000. Surprisingly enough the H screw will be 1 3/4 to 2 1/4 turns out at this point. (The limiter caps are factory set to a max of about 1 1/2 turns.) Release the throttle, allow the saw to come to idle, pull the throttle again and it should still have a quick response. Recheck the TNL RPM and adjust as necessary, by turning the H screw out to decrease and in to increase. Finally recheck the idle, and tweak as necessary. Shut the saw off, and reinstall the limiter caps, making sure they are in the approx. center of their travel - this way fine adjustments can be made later without removing the limiter caps again.

Desired RPM's: Idle: 2900-3100 and TLN: 14,000-14,200

A little theory for those that don't understand the importance of performing the adjustments in this order: While idling, the carburetor only allows fuel into the engine through the low speed circuit. During high speed operation, most fuel comes through the high speed circuit, but a small amount may potentially be coming from the low speed circuit as well. Therefore, adjusting the low speed side first is critical in obtaining an accurate high speed setting.
 
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DMShaver said:
...... (The saws are tuned in Germany on Aspen fuel, and when using US fuel, they need to run a bit richer.) .......
Click to expand...
blsnelling said:
Very well written detailed how-to Shaver!
Click to expand...

:agree2:

Maybe the Aspen fuel we allways use is the reason we never had any trouble.....:clap: :clap:

Only adjustment done so far is slightly out on the L, in an attempt to improve accelleration - it is a bit behind the 346xp and MS361 in that deparment.

The first 1/8 or so turn helped a tad, but even further out didn't add anything.......
 
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Y'all are going to laugh, but I solved this problem by getting a new Zama carb on Ebay for nine $9 dollars, and using two thin strips of aluminum can to help cinch in my carb screws. I used the Ebay carb to rebuild the 5100's carb. This saw has been modded, and I opened up the carb (make that opened up the muffler). It is an incredible little saw that starts easy, idles smooth and screams in a cut. My neighbor has been cutting with me. He's used to running an 038 and and 026, and he goes straight for the 5100 when we get to the woods, then brags about it on the way home. I'm sorry to hear that so many people are having problems with these. Wish I knew enough to help.
 
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DMShaver That was one of the best posts on carb tuning I have seen.:cheers:

However I and several others have tried adjusting the carb to no avail.. My guess is it still has an air leak at the carb boot. It also acts as if the carb is not large enough for the saw.

I'm going to make a new video that should give everyone a better idea of how the saw is behaving.

:cheers: Andy
 
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