Hot start troubles Dolmar 5105

maple man · July 02, 2015, 08:51:09 PM

I am using a Dolmar 5105 and a 110i for thinning and firewood harvesting in my woodlot. In temperatures above 70 degrees F both of these will run fine until I turn them off or they run out of fuel then can't be started unless I let them cool completely which takes as long as a half hour. I dont have any trouble except in summer heat. Any suggestions?

mad murdock · July 03, 2015, 02:34:32 AM

vapor lock. possibly a fuel additive could help reduce it. or try a higher than std octane gasoline, maybe trufuel?

ladylake · July 03, 2015, 05:33:04 AM

Try opening up the high jet some unless it's already rich, that will make it run cooler. Make sure the cooling fins are clean and under the recoil also. steve

maple man · July 03, 2015, 07:20:48 AM

I am using 50:1 91 octane gas with synthetic oil and a little marine stabil. What kind of additive would you suggest? Is trufuel the stuff they sell at the box stores for absurd prices? I have been thinking of getting some non-alcohol fuel sold for aviation. Could that help? I'm not much of a mechanic and don't own a tachometer so I'm reluctant to start adjusting the fuel mixture screws.

mad murdock · July 03, 2015, 07:54:52 AM

You can try 100LL Avgas. Same mix ratio with oil as any gas. I would agree with Ladylake, a tad bit enriched hi adjustment on the carb may help it run cooler to preclude vapor lock, if you dont feel comfortable tweaking a carb screw, try running a mix of 40:1 instead of 50:1 in the hot weather see what that does for you. Wont hurt a thing on the saw. Might smoke a touch more out the exhaust, which will help keep the bugs away.

kellysguy · July 03, 2015, 10:38:47 AM

I'd go 40:1 regardsless. Don't be scared of the carb, just do it a 1/4 turn at a time. Mark your screwdriver of whatever tool you are using as a reference. Put the tool in and engage it on the jet, mark the top of the tool facing up with a marker, turn the tool CCW 1/4 of a turn till the mark is at 9 o'clock. To make things easier on yourself do this while the saw isn't running. Turn it 1/4 at a time, then run the saw. If that adjustment makes it run worse, you know all you have to do is go back 1/4 turn in the other direction.

NOTE: If the saw won't start; turning the jets won't make it crank.

SawTroll · July 03, 2015, 07:04:11 PM

Find some non-ethanol fuel, unless you already use it.

celliott · July 03, 2015, 07:30:41 PM

Your saw's carburetor will have adjustment limiters on it. You can only turn the H and L speed jets so far. 1\4 and 3\4 turns, I believe (not totally sure, all my saws have the limiters "disabled"). Limits how lean, and rich you can adjust the carb.
Pretty sure the saw will still run alright within those adjustment limits. At the one end, it might be on the edge of too lean. Other end, probably barely too rich.
If I was you, I wouldn't be afraid to try adjusting it yourself. Just take your time, warm the saw up, and go a little bit at a time, test in the wood. Remember the amount of turns you take, and you can always put it back to where it was.

kellysguy · July 03, 2015, 07:32:40 PM

Take the cat muffler of and put the 5100 muffler on...so they say... ;)

maple man · July 03, 2015, 08:56:42 PM

Thanks for your help folks. I ran 40:1 fuel mix today and the saw started much better. I'll be trying the no ethanol fuel as well since I'm sure that's better for the saw anyway. Does the 40:1 actually run cooler or is it just less likely to vapor lock because of lower volatility? Just curious. The main thing is it works.

SawTroll · July 03, 2015, 09:24:25 PM

Quote from: maple man on July 03, 2015, 08:56:42 PM....
Does the 40:1 actually run cooler or is it just less likely to vapor lock because of lower volatility? Just curious. The main thing is it works.

I don't really know that - but it surely makes the saw run a bit leaner, as the extra oil displaces fuel in the fuel to air mix.

zandoval · July 04, 2015, 03:20:55 AM

Quote from: mad murdock on July 03, 2015, 07:54:52 AM
...try running a mix of 40:1 instead of 50:1 in the hot weather...

Guys running the brush trucks here in Central Texas run 40:1 in their 50:1 saws during the heat of the summer - They have told me that high heat and humidity greatly effect their saws... Especially when running 10% ETOH gas... They also added that out in west Texas they did not have to do this...

ladylake · July 04, 2015, 04:18:51 AM

Saws need to be tuned when switching from good gas to ethanol laces gas and vice versa. Ethanol makes them run leaner. Steve

kellysguy · July 04, 2015, 06:33:09 AM

Quote from: SawTroll on July 03, 2015, 09:24:25 PM

I don't really know that - but it surely makes the saw run a bit leaner, as the extra oil displaces fuel in the fuel to air mix.

Not nessicarily, you're just replacing some fuel with oil and the o2 level is still the same. Since the oil is combustible, it still needs and uses the O2 the "displaced" fuel would have needed. Given the fact that the oil has more BTU's in it and it burns at a higher temp, it actually will "richen" the mix while reducing overall combustion temperature by absorbing heat till gets to it's vaporization/flashpoint.

It's like Freon or evaporating water, if you will. I can't remember the name of the effect.

ladylake · July 04, 2015, 08:12:53 AM

I think with more oil the viscosity will be thicker and not run through the jets as fast but from 50 to 40 to 1 not a lot of difference. Steve

kellysguy · July 04, 2015, 08:50:27 AM

True but as long as the "thickening agent" is oxidizable and/or absorbs heat and CCT's are kept in an acceptable range, any reduction in flow is irrelevant. Excessive heat is the problem. As long as CCT are where they need to be, you can do whatever you want....within power and lubrication requirements of course.

SawTroll · July 04, 2015, 05:25:00 PM

Quote from: kellysguy on July 04, 2015, 06:33:09 AM
Not nessicarily, you're just replacing some fuel with oil and the o2 level is still the same. Since the oil is combustible, it still needs and uses the O2 the "displaced" fuel would have needed. Given the fact that the oil has more BTU's in it and it burns at a higher temp, it actually will "richen" the mix while reducing overall combustion temperature by absorbing heat till gets to it's vaporization/flashpoint.

It's like Freon or evaporating water, if you will. I can't remember the name of the effect.

I've never "heard" that thory before, and I'm quite sure I would have if it is correct - as this has been discussed a zillion times on different forums?

Anyway, retuning the carb will correct any issue, so the need to do that when changing the fuel mix really is the point!

kellysguy · July 04, 2015, 07:49:37 PM

Quote from: SawTroll on July 04, 2015, 05:25:00 PM
I've never "heard" that theory before, and I'm quite sure I would have if it is correct -

My mistake, I was unaware in the engineering fields I have been professionally involved in, that you were in fact the definitive authenticator of any and all factual information. The next time I am involved in any aerospace prototype rocket designs for NASA, oil rig, tanker and platform model design and testing for major oil companies or professionally building BMW or Ferrari race cars.... or even the next MENSA meeting; I'll be sure to let everyone know to contact you first for the validity of any information they may have.... ;)

Of course... myself nor non of my past, present or future engineering colleagues would be qualified to discuss something as advanced as the latent heat energy required to phase shift 2 stroke oil nor the thermodynamics of something so sophisticated....as a chainsaw... :

ladylake · July 05, 2015, 07:53:54 AM

It's hard for me to believe fuel mixed at 16 to 1 will flow as fast through a jet as fuel mixed at 50 to 1. Steve

kellysguy · July 05, 2015, 10:22:21 AM

Who said that it would? I never implied anything close to that nor do I see where anyone did either. What I said was due to the increase potential BTU content of the oil, any reduction of flow is irrelevant. That doesn't mean it doesn't slow down any, it means any minimal loss of velocity doesn't matter in overall BTU content. The only problem would be that replacing too much of HC's "A" with HC's "B" that require greater heat and pressure to burn efficiently into a system designed for "A" would result in loss of combustion and power.

What I just said was basically; you can put some diesel in gasoline and an engine will run fine, however; if you put too much it won't.

In either case, diesel or 2 stroke oil; you need the heat and pressure produced by the burning gasoline in order to burn the other component.

I think the problem is getting hung up on the idea of "lean" as an absence of gas instead of an absence of fuel, which is actually overall bTU content, but I di understand where you guys are coming from. While it is absolutely correct to "lean" a mixture of gas by increasing oil, that doesn't mean you have created automatically created a "lean" condition with excessive heat. I also didn't state the carb wouldn't have to be adjusted changing ratios either.

Oil has a higher potential BTU content per # than gasoline, which has higher BTU's than alcohol. This is why less power is produced ethanol then straight gas. This is also why a diesel produces more power than a gasoline engine, however; needs a completely different set of parameters to operate. The oil still needs O2 to burn though.

My earlier statement was purposely over simplified for clarity simply because there are many other factors at work that go far beyond the scope of this thread.

All I said when the question was posed to why does it run cooler and why does increasing the oil content overcome heat; is that the increased content of oil requires more heat to be absorbed in order for the oil to reach a combustible state. In order for matter to undergo a phase shift from solid to liquid or liquid to gas, heat is needed. This heat is taken from it's surroundings which has a cooling effect. (This is how your A/C works.) Oil requires more heat to undergo this shift than gas, this needed heat is removed from it's surroundings. Even if it doesn't fully undergo this shift, it still is absorbing heat. Oil in a 4 stroke can absorb up to 80% of the hear produced from combustion. Just because there are two cycles less doesn't mean the oil won't absorb heat. (Oil was used to keep ignition coils and transformers cool for a reason.) So even if the oil doesn't burn, it's going out the exhaust along with the heat it has collected.

I can see where it may have become confusing to some as I was talking about two different things at the same time.

So, "lean less gas" Absolutely. "Lean", less fuel or power potential, no.; BUT, it needs to be at the correct temp to achieve it.

A good point of study is Smokey Yunick's hot air engine. It will change the way you look at hot and lean.

I get that there are a lot of guys who don't care why, just turn the screw till it doesn't what you want it to; and there is absolutely nothing wrong with that.
(I'm actually in that camp now due to a brain injury from an accident last year.) That being said, I'm tired of talking about this.

clww · July 05, 2015, 11:14:43 AM

Quote from: kellysguy on July 05, 2015, 10:22:21 AM
A good point of study is Smokey Yunick's hot air engine. It will change the way you look at hot and lean.

"Best *DanG Garage In Town!" ;)

kellysguy · July 05, 2015, 11:20:28 AM

I "chased" that (Admin language edit) for 30 years trying to study his work. Finally the internet came about and I bought copies of the patents and studied the carp outta 'em. Finally, I came up with my own design unlike anything the automotive industry has EVER seen before...only to find out Bruce Crower designed the same EXACT thing four years earlier. I think I cried for a year...

JohnG28 · July 05, 2015, 03:28:07 PM

The idea of 2 stroke oil is to not burn, which is evident in the fact they don't blow up upon startup. The oil is not a replacement for gas. Sorry everyone isn't an aerospace engineer here but a lot of people do know their chainsaws as well as plenty more. :

ladylake · July 05, 2015, 05:01:28 PM

This thread is about making simple adjustments to the carb, not rocket science. Way too many products are over engineered. Steve

kellysguy · July 06, 2015, 05:56:56 PM

Quote from: JohnG28 on July 05, 2015, 03:28:07 PM
The idea of 2 stroke oil is to not burn, which is evident in the fact they don't blow up upon startup.

So.... I guess the reason it's formulated to be ashless was just a mistake.... :

It was designed to be a COMSUMABLE lubricate. It is in fact designed to burn which is why regular motor oil is no longer used in premixing...

You do see the blue smoke...right?!?!?

What do you think that is, magic blue wood fairies being cut open? :D

You obviously have no idea what I said regarding the gas vs oil vs fuel thing because you're completely off-base from what I stated, so I'm not going to waste my time trying to explain it further.

As you mentioned earlier, some folks may know more than others.... so folks really should just stick to what they know best before they have a beef against someone else who knows more in a particular area, otherwise, all they'll do is make themselves look foolish ;)

"Even fools are thought wise if they keep silent" Proverb 17:28....... ;)

(I mean really; that is the definition of ignorance. Just how stupid would I make myself look trying to tell a logger how to log?! I guess Twain was right but for the life of me, I have no idea why you continue to try to argue with me. Less I digress...)

BTW, the whole purpose of my post (because that has been obviously missed) was that, "I read it on the internet so it must be true" isn't considered be an educated or valid reason to dismiss information.

Matter of fact, that statement is a running joke on MANY forum.

No one is trying to take anything away from anyone, however; just because someone has never heard anything explained like that before, doesn't automatically mean it the explanation is invalid. Others may have knowledge beyond their own personal experience.

THAT WAS THE POINT......

The OP posed the question, troll said he didn't know and I offered an explanation. I have no idea why people are having a problem with that. I would think that would be welcomed information but apparently not; lest I disturb someone's belief in the all-powerful blue wood fairy... :

Troll knows a lot about saws (obviously) and I am quite certain he knows a lot more than I in certain aspects of that area. I'm quite sure troll knows things I've never heard of before, but I'm certainly not ignorant nor arrogant enough to dismiss him just solely based on that fact.. ESPECIALLY if I can't offer a scientific argument otherwise..... ;) I certainly wouldn't EVER try to discount anyone's personal knowledge or experience and I would expect to have that courtesy returned in-kind......and you can bet your (admin language edit) that I won't hesitate to take someone to task when they don't... ;)

...and this certainly doesn't involve anyone else....

...and as I stated earlier, I have explained all I care to on this subject.

beenthere · July 06, 2015, 07:33:45 PM

Are you sure this time? ;D

JohnG28 · July 06, 2015, 08:49:37 PM

Well your arrogance for one sure lends to a lack of character. And I couldn't care less as to what your opinion or explanation is, I guess that's what I'm getting at. I too possess an engineering degree. I don't, however, believe that makes me the smartest or most knowledgeable person at all times. :

Your general demeanor alone discredits most of what you have to say IMO as well, but maybe that's me. :

I'd be surprised if that was the case though. :D

kellysguy · July 06, 2015, 09:09:43 PM

Quote from: JohnG28 on July 06, 2015, 08:49:37 PM
I too possess an engineering degree.

Once again you have been proven wrong and instead of posing an intelligent response, you use attack personally because you have lost. You have done that every single time.... and it's in conversations that don't even involve you... Yeah, you're obviously a man with a profound sense of character....

It is also clear you do not have a grasp of the definition of arrogance as you would see exactly where it lies in this thread.....but instead pick and choose the definition to suit whatever loosing stance you choose to take...

I can't even begin to imagine exactly what engineering discipline believes that two stroke oil doesn't burn but... is in fact turned into blue fairy farts... ...but you're an engineer..... :D

As I stated before, this isn't the first time I've had a problem with you. The only thing you have shown is you can't follow a train of thought or direction... BUT you enjoy the sound of your own voice. I've yet to see where you've had anything interesting or intelligent to add to a conversation, yet you always seem to find something non sequitur to say out of what has to be a constant need for attention.

We all hear you Mr. Engineer and you have our complete attention; blue fairy farts it is.... :D

Did I mention I'm a big fan of Twain? ;)

kellysguy · July 06, 2015, 09:11:37 PM

Quote from: beenthere on July 06, 2015, 07:33:45 PM
Are you sure this time? ;D

You remind me a lot of myself. I like you! ;D

346xp · July 06, 2015, 09:12:56 PM

Quote from: JohnG28 on July 06, 2015, 08:49:37 PM
Well your arrogance for one sure lends to a lack of character. And I couldn't care less as to what your opinion or explanation is, I guess that's what I'm getting at. I too possess an engineering degree. I don't, however, believe that makes me the smartest or most knowledgeable person at all times. : Your general demeanor alone discredits most of what you have to say IMO as well, but maybe that's me. : I'd be surprised if that was the case though. :D

X2 so true 8)

kellysguy · July 06, 2015, 09:23:57 PM

Quote from: 346xp on July 06, 2015, 09:12:56 PM

X2 so true 8)
[/quote]

Right, so being flippant and arrogant enough to say someone is wrong just because someone has never heard it before is ok.....but to respond to that flippant comment is wrong.....

Kinda funny how it's ok for some folks but not for others....and you claim to know the definition of character....

Says a lot about you both more than it ever will of me....and the fact I have to point that out only proves it all the more....

Such a shame.

I actually have respect for troll, both for his knowledge base and the fact he didn't try to defend what he did. The fact you both defend that behavior clearly shows you have no idea of what character truly is. At least he's man enough to know right from wrong.

But that doesn't matter, right? One of your buddies is sore because I proved him wrong so just pile on when it doesn't even involve either of you.....

.....yeah, you have character alright..... :

NOTE: Just because you are a charater ...doesn't mean you have character...

Hilltop366 · July 06, 2015, 11:00:31 PM

Quote from: maple man on July 03, 2015, 08:56:42 PM
Thanks for your help folks. I ran 40:1 fuel mix today and the saw started much better. I'll be trying the no ethanol fuel as well since I'm sure that's better for the saw anyway. Does the 40:1 actually run cooler or is it just less likely to vapor lock because of lower volatility? Just curious. The main thing is it works.

Maple man welcome to the forum, glad you got your saw working better.

Trying to follow along on the science of all of this and I think I got some of it but it gets hard to follow with some of the acronyms that are used and when words like rich and lean mixture are used without adding "fuel/air" or "fuel/oil" after it to be able to tell what is being talked about. Perhaps these things would have saved some confusion and saved this thread from taking a turn for the worst.

Hilltop366

luvmexfood · July 07, 2015, 06:57:45 AM

Quote from: maple man on July 02, 2015, 08:51:09 PM
I am using a Dolmar 5105 and a 110i for thinning and firewood harvesting in my woodlot. In temperatures above 70 degrees F both of these will run fine until I turn them off or they run out of fuel then can't be started unless I let them cool completely which takes as long as a half hour. I dont have any trouble except in summer heat. Any suggestions?

Let's try to help the original poster solve his saw problem and not have a pee pee contest about who is right and who is wrong.

WDH · July 07, 2015, 07:24:45 AM

Kellysguy,

It is time for you to change your tone and demeanor. This is not a contest where someone wins and someone loses as has been pointed out. I respectfully ask that you step back and think about how you are interacting in this case.

JohnG28 · July 07, 2015, 03:55:43 PM

:D :D Guess it's not just me! Sorry to the OP, didn't mean to hijack your thread. Welcome to the forum!

346xp · July 10, 2015, 08:42:13 AM

Quote from: WDH on July 07, 2015, 07:24:45 AM
Kellysguy,

It is time for you to change your tone and demeanor. This is not a contest where someone wins and someone loses as has been pointed out. I respectfully ask that you step back and think about how you are interacting in this case.

Good idea thank you 8) 8)

Hogeye265 · March 14, 2017, 11:38:26 PM

The cat muffler is the main problem we notice on the 5105. The muffler off a 5100 or a 510 is the same mount. Try it and I think you'll see for yourself how much it makes a difference.

ehp · March 16, 2017, 04:02:51 PM

set the carb richer on the 5105, those saws have a very tight crankcase volume so a lot of heat is made in the crankcase , run the 5105 for almost its tank bucking up firewood , when you go to shut that saw off take top cover off and put your ear up to the air filter then shut the saw off, you will hear what ever gas is in the crankcase boiling for a couple seconds , that's how tight in volume those crankcases are .

5000+ · March 20, 2017, 03:18:29 PM

Most likely cause is winter grade fuel used on a warm day. No easy cure, but anything you can do to lower the engines temp is a plus. Even letting the saw idle for a couple of minutes before shutting off may help. Also making sure the flywheel area and engineand cylinder are clean.