Dolmar 5105S - what idle speed is everyone running?

[eugene89us]

Good morning, everyone. I noticed on these threads that most folks with Dolmar 5105S or similar saws, like PS-510 and PS-5100, all seem to be running at a higher RPM. My MS 261 Stihl runs at 2800 RPM per Stihl recommendation with high jet at 14,000 RPM.

I have read here that high-speed coil Dolmars can run up to 14,500, but they perform well running between 13,800 and 14,200. For sake of preserving the saw's life, I will probably tune the high jet to run around 13,800-13,900 RPM, that will give me plenty of room for error.

I also understand the process of adjusting L and S screws. For Stihl, the process is easy in my opinion. You raise the RPM with speed screw up to 3300 (500 RPM above recommended), move around the L screw until you find the highest RPM. After that, speed screw drops back down to 3300 RPM, and finally the L screw finishes by enriching the mix back down to recommended 2800 RPM. It sounds complex, but closely follows highly recommended Chainsaw tuning video by Steve's Small Engine channel. He raises speed screw until chain starts to move (which follows Stihl's recommendation to raise the speed first), then he find the sweet spot of highest RPM with L screw, and then he enrichens L screw until the speed JUST starts to drop, and finished with S screw to stop chain from spinning. That is very similar, I think. One is the tach method, the other is the ear method.

What I am not certain about is what should the final idle RPM be at? The manual for 5100 and 5105 says 2500 is the idle RPM. Most folks posting here run around 2900-3000 RPM idle. Is there a specific reason for tuning it to run that fast at idle?

 

[huskihl]

Slow enough that the chain doesn’t spin. The number doesn’t matter as long as it idles OK and there are no clutch spring or bearing issues

 

[eugene89us]

I am curious as to the average of what everyone runs. But I presume if I can make it start easily and run without stalling or flooding on drop test at 2500 RPM, that would be perfectly acceptable? I don't think I found a single thread on forums of anyone running these saws below 3000 rpm. I didn't know if there was a reason. After all, I don't think clutch activates until 3500-3600, therefore to avoid chain spin, you can run it decently high idle and still remain within safety margins.

 

[huskihl]

Don’t really think most are checking with a tach. If it starts, idles, stays running after a cut, and the chain doesn’t spin I think most consider that a win regardless of what the number says

 

[Brufab]

Don’t really think most are checking with a tach. If it starts, idles, stays running after a cut, and the chain doesn’t spin I think most consider that a win regardless of what the number says

+1

 

[eugene89us]

I am a man of science, I like hard and fast figures. But I noticed I can tune the chainsaw to run at 2500 rpm, except it would run quite rough. It would have quick throttle response and it would not die when suddenly inverted, but it was sounding hammery. When I raise RPM to around 2800, it runs pretty well. What I did is I followed Stihl guidance by raising S screw to 3300 RPM, then finding the fastest RPM with L screw, which I found to be around 3600 RPM. Then I reduced S screw down to 3300 RPM again, and then richened L screw down to 2800 RPM. Will test it out in the wood this afternoon. Wish me luck.

 

[Brufab]

Seems fast. But I'm no expert

 

[eugene89us]

My Stihl MS 261 runs at 2800 idle and 14,000 high. This Dolmar is meant to run 2500 idle and 14,500 fast. Of course, they burn out at 14,500 and run rougher at 2500. I decided to disregard the label on the saw - it is orange, so it must be Stihl. Hence 2800 for idle and 14,000 for high. Haha. I may regret this decision, but a famous saying, "He who does not risk, does not drink Champagne."

 

[huskihl]

I am a man of science, I like hard and fast figures. But I noticed I can tune the chainsaw to run at 2500 rpm, except it would run quite rough. It would have quick throttle response and it would not die when suddenly inverted, but it was sounding hammery. When I raise RPM to around 2800, it runs pretty well. What I did is I followed Stihl guidance by raising S screw to 3300 RPM, then finding the fastest RPM with L screw, which I found to be around 3600 RPM. Then I reduced S screw down to 3300 RPM again, and then richened L screw down to 2800 RPM. Will test it out in the wood this afternoon. Wish me luck.

Two-strokes don’t go by numbers though. It runs on what feels good that day depending on the fuel, oil, air temperature, humidity, elevation… they don’t do well with fixed numbers because the parameters around them are always changing

 

[eugene89us]

Well, I am not saying that you tune the saw once and done, I understand it may require a re-tune as time goes by. However, it is still good to have some kind of baseline. For my Stihl, I follow the official guidance on tuning and the saw runs impeccably. Once in a while with change in seasons it will start sounding different, so I repeat the procedure and it runs impeccably again. But I do not want to constantly tune a saw, I want it at least to stay as-is for the season. To me a saw sounds good if it runs smoothly. I hate seeing a saw that shakes all around as it sits idling. Dolmar at 2500 was shaking, when I returned to 2800, it was nice and smooth. Fine shake of course, but nothing coarse like I saw at recommended RPM