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Stihl 170 Chain Saw Carbon problem
#1
C
chzuck
C
chzuck
I must say I am less than pleased with my Stihl 170 chain saw. I bought one because of their supposedly great reputation. I didn't even run a gallon of fuel through the saw and the coil failed. Fortunately it was under warranty. I am probably just starting on my 3 gallon of fuel and the saw lost power. Turns out the spark arrestor screen was plugged with carbon. I am using Stihl Ultra oil. Is this normal for this saw?
#2
B
bertsmobile1
B
bertsmobile1
The saw is either running very very rich or you have mixed the fuel with way too much oil.
#3
C
chzuck
non-adjustable carburetor and oil is 1 bottle to 1 gallon of gas and air cleaner is clean. Probably will try different oil.
C
chzuck
The saw is either running very very rich or you have mixed the fuel with way too much oil.
non-adjustable carburetor and oil is 1 bottle to 1 gallon of gas and air cleaner is clean. Probably will try different oil.
#4
BlazNT
Some bottles are for 2 gallons of gas. For one gallon of gas it is like 6 oz.
BlazNT
non-adjustable carburetor and oil is 1 bottle to 1 gallon of gas and air cleaner is clean. Probably will try different oil.
Some bottles are for 2 gallons of gas. For one gallon of gas it is like 6 oz.
#5
C
chzuck
The bottles (2.6 oz) I have say makes 1 gallon.
C
chzuck
Some bottles are for 2 gallons of gas. For one gallon of gas it is like 6 oz.
The bottles (2.6 oz) I have say makes 1 gallon.
#6
BlazNT
BlazNT
Sorry I was still thinking of 40 to 1 for 2 gallon. 2.6 is for 50 to 1 and one gallon.
#7
B
bertsmobile1
B
bertsmobile1
As it is a new saw. take it back to the shop.
There could be a problem with the engine.
Chain saws spin very fast so a coil that only fires 3 out of 4 revs will not be noticed by the operator but make a big difference to the emissions.
The carb is adjustable, just not by the owner.
There could be a problem with the engine.
Chain saws spin very fast so a coil that only fires 3 out of 4 revs will not be noticed by the operator but make a big difference to the emissions.
The carb is adjustable, just not by the owner.
#8
C
chzuck
C
chzuck
Well, it is not brand new and under warranty anymore. I bought it in 2012.
I emailed Stihl about the issue and below is their reply.
Two stroke engines like the one in your MS170 use an ignition principle called "loop scavenging". This means that when the fuel is cycled through the four transfer ports of the cylinder from the bottom to the top of the combustion chamber, it begins to swirl in a widespread pattern to insure that as much of the fuel burns as possible when the unit fires the ignition spark.
Unfortunately, it doesn't matter how efficient the design of the engine is in the two-cycle format because a small amount of raw fuel is going to escape with the burnt exhaust gasses each time the engine fires. This raw gas/oil mix tends to collect on the fire arrestor screen of the muffler, and over time it will accumulate and cause an obstruction. When this happens, the obstruction will not allow the exhaust gasses to escape, causing them instead to bounce off and push back through the combustion chamber and, if the blockage is severe enough, out of the carburetor venturi onto the air filter.
The issue can be compounded if the engine is feathered or run at part throttle for extended periods of time. The fuel cannot burn efficiently when the engine is run in this manner, so the screen can clog much faster.
The best way to cure this problem, as you know, is to remove the screen from the muffler and check it for carbon build-up. If carbon is present, simply pass a wire brush over the screen from all sides until the debris is removed. Then re-install it back into the muffler and try your starting procedures once more.
I think I may try another brand oil when the Stihl Ultra is gone. Not sure if my Tanaka string trimmer has a screen, but I have had that for almost 20 years and have never had that kind of problem and it runs 25:1 mix. And I could remove the screen. None of my other, vintage saws have that fine of a screen and I only cut wood on my property with my saws.
I emailed Stihl about the issue and below is their reply.
Two stroke engines like the one in your MS170 use an ignition principle called "loop scavenging". This means that when the fuel is cycled through the four transfer ports of the cylinder from the bottom to the top of the combustion chamber, it begins to swirl in a widespread pattern to insure that as much of the fuel burns as possible when the unit fires the ignition spark.
Unfortunately, it doesn't matter how efficient the design of the engine is in the two-cycle format because a small amount of raw fuel is going to escape with the burnt exhaust gasses each time the engine fires. This raw gas/oil mix tends to collect on the fire arrestor screen of the muffler, and over time it will accumulate and cause an obstruction. When this happens, the obstruction will not allow the exhaust gasses to escape, causing them instead to bounce off and push back through the combustion chamber and, if the blockage is severe enough, out of the carburetor venturi onto the air filter.
The issue can be compounded if the engine is feathered or run at part throttle for extended periods of time. The fuel cannot burn efficiently when the engine is run in this manner, so the screen can clog much faster.
The best way to cure this problem, as you know, is to remove the screen from the muffler and check it for carbon build-up. If carbon is present, simply pass a wire brush over the screen from all sides until the debris is removed. Then re-install it back into the muffler and try your starting procedures once more.
I think I may try another brand oil when the Stihl Ultra is gone. Not sure if my Tanaka string trimmer has a screen, but I have had that for almost 20 years and have never had that kind of problem and it runs 25:1 mix. And I could remove the screen. None of my other, vintage saws have that fine of a screen and I only cut wood on my property with my saws.
#9
B
bertsmobile1
B
bertsmobile1
OK,
I was under the impression it was a new saw.
Clean the screen and put it back.
If it is a problem then leave it off.
It is a spark arrestor so will not make much difference to the saw except a slight drop in back pressure.
A lot of owners toss them
The only big problem is the screen prevents mud pluggers nesting in the muffler so if you leave it off & mud pluggers are in your area tie a bag around the engine or store the saw in a box when not in use.
Still sounds like it is running rich or missing but you need some expensive gear to test it.
You can look the parts break down for your carb to find the hidden adjustments on the carb makers web sites not the Stihl one.
As it is out of warranty it will not matter that the tell tales are broken.
Just be ware of adjusting it too lean as slightly lean will over heat and wreck the bore in no time flat.
You already know the outcome of too rich.
I was under the impression it was a new saw.
Clean the screen and put it back.
If it is a problem then leave it off.
It is a spark arrestor so will not make much difference to the saw except a slight drop in back pressure.
A lot of owners toss them
The only big problem is the screen prevents mud pluggers nesting in the muffler so if you leave it off & mud pluggers are in your area tie a bag around the engine or store the saw in a box when not in use.
Still sounds like it is running rich or missing but you need some expensive gear to test it.
You can look the parts break down for your carb to find the hidden adjustments on the carb makers web sites not the Stihl one.
As it is out of warranty it will not matter that the tell tales are broken.
Just be ware of adjusting it too lean as slightly lean will over heat and wreck the bore in no time flat.
You already know the outcome of too rich.
#10
C
chzuck
C
chzuck
Thank you for the input. I was under the impression there were no adjustments like some of our newer lawn mower carburetors. You have a point about being too rich. It should not have clogged that screen in less than 3 gallon of gas.
#11
B
bertsmobile1
B
bertsmobile1
Depend how you are using it.
If you are using it with a blunt blade , labouring the engine with a wide open throttle while applying your whole body weight to try & make it cut then yes 3 gallons will be more than enough to clog the screen.
I can always tell when hubby has sent wifey down to me with his chain saw.
The teeth will be rounded off , the paint on the bar will be burned off and there will be a deep gouge in the blade adjacent to the spikes where he has been forcing a blunt blade to do " just one more cut".
OTOH a woman's saw will require nothing more than 2 strokes of a blunt file to return a chain to razor sharp and the bar will look like it was bought yesterday.:laughing:
If you are using it with a blunt blade , labouring the engine with a wide open throttle while applying your whole body weight to try & make it cut then yes 3 gallons will be more than enough to clog the screen.
I can always tell when hubby has sent wifey down to me with his chain saw.
The teeth will be rounded off , the paint on the bar will be burned off and there will be a deep gouge in the blade adjacent to the spikes where he has been forcing a blunt blade to do " just one more cut".
OTOH a woman's saw will require nothing more than 2 strokes of a blunt file to return a chain to razor sharp and the bar will look like it was bought yesterday.:laughing:
#12
C
chzuck
C
chzuck
I have been cutting long enough that when I start seeing saw dust instead of saw chips that it's time to sharpen the chain. My old Super 2 Homelite was a better saw in its day than this Stihl ever will be!
#13
M
Mad Mackie
M
Mad Mackie
Remove the screen and throw it away. Carefully clean the exhaust port.
I use 91-93 octane gasoline in all my small power equipment.
I have Stihl blowers, string trimmers and hedge trimmers, but I have Husqvarna chainsaws.
I use 91-93 octane gasoline in all my small power equipment.
I have Stihl blowers, string trimmers and hedge trimmers, but I have Husqvarna chainsaws.
#14
Boobala
Boobala
Why is it so hard for some folks to try using the synthetic 2 cycle oils, ???? I've been using OPTI-2 ( http://opti2-4.com/index.php?dispatch=categories.view&category_id=165 ) for about 15 years now , NEVER a problem ...... NO smoke , NO clogged exhaust and hardly any carbon build-up in the cylinder. I guess the mention of APPROX. 100 to 1 ratio scares the hell outa folks ... There are several good synthetics out there, you may just want to try it for a change to the better......... Boobala :thumbsup:
P.S. might want to see their EXTENDED warranty for using their 4 cycle oil in new engines
http://opti2-4.com/images/thumbnails/images/Double Engine Warranty information.pdf
P.S. might want to see their EXTENDED warranty for using their 4 cycle oil in new engines
http://opti2-4.com/images/thumbnails/images/Double Engine Warranty information.pdf
#15
C
chzuck
C
chzuck
I do use a full synthetic - Stihl Ultra. Thanks for the recommendation. My local hardware store is supposed to carry that according to the Opti website.Why is it so hard for some folks to try using the synthetic 2 cycle oils,
#16
J
Jack17
J
Jack17
MS170 is an excellent light duty saw. I've had it for over 15 years and gave it away when I bought MS251CE. I've never had any problems with spark screen getting clogged up with carbon but...and given that your carburetor adjustment and fuel mix is correct could in fact be just the nature of the beast! Good example is my Stihl blower. Brand new, one tank of gas went thru it and screen was all clogged up. Lost all RPMs, barely idling. Took the screen out, cleaned it, put it back in, another tank of gas thru it and same thing all over again. All in all, screen is permanently out of the muffler and and she runs like new. I also use Sthil synthetic 2-cycle oil not only because it is a good product but also because Stihl gives one extra year of factory warranty if you buy it together with equipment purchase.
BTW, like the other guys told you about keeping the chain sharp...keep it sharp! This newer tool Stihl sells to sharpen chains cost about $45 or so and it's worth every penny...trust me!
BTW, like the other guys told you about keeping the chain sharp...keep it sharp! This newer tool Stihl sells to sharpen chains cost about $45 or so and it's worth every penny...trust me!
#18
C
chzuck
Every thing I have seen says the carburetor is not adjustable.
C
chzuck
MS170 is an excellent light duty saw. I've had it for over 15 years and gave it away when I bought MS251CE. I've never had any problems with spark screen getting clogged up with carbon but...and given that your carburetor adjustment and fuel mix is correct could in fact be just the nature of the beast! Good example is my Stihl blower. Brand new, one tank of gas went thru it and screen was all clogged up. Lost all RPMs, barely idling. Took the screen out, cleaned it, put it back in, another tank of gas thru it and same thing all over again. All in all, screen is permanently out of the muffler and and she runs like new. I also use Sthil synthetic 2-cycle oil not only because it is a good product but also because Stihl gives one extra year of factory warranty if you buy it together with equipment purchase.
BTW, like the other guys told you about keeping the chain sharp...keep it sharp! This newer tool Stihl sells to sharpen chains cost about $45 or so and it's worth every penny...trust me!
Every thing I have seen says the carburetor is not adjustable.
#19
J
Jack17
J
Jack17
It looks like carb on MS170 is adjustable: Page 41
https://www.stihlusa.com/WebContent...TIHL-MS-170-180-Owners-Instruction-Manual.pdf
https://www.stihlusa.com/WebContent...TIHL-MS-170-180-Owners-Instruction-Manual.pdf
#20
J
Jack17
J
Jack17
Also, simple things that could contribute to carbon build up like...dirty air filter and idling for a long time.
#21
C
chzuck
https://youtu.be/gUyOpYa25cM
C
chzuck
That adjustment is for idle speed. If there are any other adjustments, they are well hid. I watched the YouTube video listed below and looked as he rotated the carb and did not see any adjustments other than idle speed.It looks like carb on MS170 is adjustable: Page 41
https://www.stihlusa.com/WebContent...TIHL-MS-170-180-Owners-Instruction-Manual.pdf
https://youtu.be/gUyOpYa25cM
#22
C
chzuck
Possibly too long idling. I am going to pay more attention this time and see how long it takes to clog up.
C
chzuck
Also, simple things that could contribute to carbon build up like...dirty air filter and idling for a long time.
Possibly too long idling. I am going to pay more attention this time and see how long it takes to clog up.
#23
T
Tyy
T
Tyy
Your saw is running much to rich , these screens normally need cleaning perhaps once a yr . if you use your saw perhaps 100 hrs a yr. Most consumers never use their units than much . Amsoil Sabre is the best Premium Grade Synthetic oil made . Opti -2 or Stihl Ultra are also premium oil . Pull you spark plug and I would bet it is dark brown or black , indicating much to rich of oil ratio . 50:1 is more than adequate for your model . The carb is adjustable once you remove the limitor caps depending on which yr your saw is will determine which adjuster tool you will need , Pacman , splined hex ..etc ! These tools are onine for 2-3 bucks or you can slot yours with dremel and use a small slotted screwdriver to adjust you jets to lean out your high speed jet .
l
l
#24
C
chzuck
OK, I will say this again, this carburetor has only one adjustment - idle speed. I used and am using Stihl Ultra at the recommended amounts. I took a look at the carburetor and there are two empty cavities where the L & H adjustment needles would be. I contacted a Stihl rep and the only thing he said was maybe I allowed it to idle too much. So now I am shutting it off when not cutting. Now that it is out of warranty I plan to try other oils, such as Opti-2.
C
chzuck
Your saw is running much to rich , these screens normally need cleaning perhaps once a yr . if you use your saw perhaps 100 hrs a yr. Most consumers never use their units than much . Amsoil Sabre is the best Premium Grade Synthetic oil made . Opti -2 or Stihl Ultra are also premium oil . Pull you spark plug and I would bet it is dark brown or black , indicating much to rich of oil ratio . 50:1 is more than adequate for your model . The carb is adjustable once you remove the limitor caps depending on which yr your saw is will determine which adjuster tool you will need , Pacman , splined hex ..etc ! These tools are onine for 2-3 bucks or you can slot yours with dremel and use a small slotted screwdriver to adjust you jets to lean out your high speed jet .
l
OK, I will say this again, this carburetor has only one adjustment - idle speed. I used and am using Stihl Ultra at the recommended amounts. I took a look at the carburetor and there are two empty cavities where the L & H adjustment needles would be. I contacted a Stihl rep and the only thing he said was maybe I allowed it to idle too much. So now I am shutting it off when not cutting. Now that it is out of warranty I plan to try other oils, such as Opti-2.
#25
Boobala
Way to go... just be sure to use a bit more than 1 (one) ounce (oz.) per GALLON of gas....... I use approx 1.2 oz. of OPTI-2 per gallon , if your problem persists I would remove the spark arrestor screen (unless you're cutting in a thick patch of woods ............
http://opti2-4.com/index.php?dispatch=categories.view&category_id=165
Keep us informed, it might still be another issue...... Boobala ....:thumbsup:
P.S. I just LOVE the B/S your rep told you about lettig it idle too long...... I have let my running equipment idle for more than 10-15 min at a time ....... ( moving branches / equipment etc. ) and never a problem ........
Boobala
OK, I will say this again, this carburetor has only one adjustment - idle speed. I used and am using Stihl Ultra at the recommended amounts. I took a look at the carburetor and there are two empty cavities where the L & H adjustment needles would be. I contacted a Stihl rep and the only thing he said was maybe I allowed it to idle too much. So now I am shutting it off when not cutting. Now that it is out of warranty I plan to try other oils, such as Opti-2.
Way to go... just be sure to use a bit more than 1 (one) ounce (oz.) per GALLON of gas....... I use approx 1.2 oz. of OPTI-2 per gallon , if your problem persists I would remove the spark arrestor screen (unless you're cutting in a thick patch of woods ............
http://opti2-4.com/index.php?dispatch=categories.view&category_id=165
Keep us informed, it might still be another issue...... Boobala ....:thumbsup:
P.S. I just LOVE the B/S your rep told you about lettig it idle too long...... I have let my running equipment idle for more than 10-15 min at a time ....... ( moving branches / equipment etc. ) and never a problem ........
#26
Boobala
Boobala
Got curious, I really despise any non-adjustable equipment. Anyway I found this ...... you MUST read the ENTIRE description ..........scroll down the page ..... this may be the cheap way out , a little modification to access the screws is all that seems necessary ....... as Trump says...... " whadda ya got to lose "...... :thumbsup:
............https://www.amazon.com/STIHL-MS170-MS180-Carburetor-Chainsaw/dp/B00CMOBTDE
............https://www.amazon.com/STIHL-MS170-MS180-Carburetor-Chainsaw/dp/B00CMOBTDE
#27
C
chzuck
I do want to check with the techs at the dealer where I bought the saw, just have not taken the time to do that yet.
C
chzuck
That rep was probably an engineer and not a mechanic. I dealt with engineers for years where I worked.Way to go... just be sure to use a bit more than 1 (one) ounce (oz.) per GALLON of gas....... I use approx 1.2 oz. of OPTI-2 per gallon , if your problem persists I would remove the spark arrestor screen (unless you're cutting in a thick patch of woods ............
http://opti2-4.com/index.php?dispatch=categories.view&category_id=165
Keep us informed, it might still be another issue...... Boobala ....:thumbsup:
P.S. I just LOVE the B/S your rep told you about lettig it idle too long...... I have let my running equipment idle for more than 10-15 min at a time ....... ( moving branches / equipment etc. ) and never a problem ........
I do want to check with the techs at the dealer where I bought the saw, just have not taken the time to do that yet.
#28
T
Tyy
T
Tyy
Ok let me say this again , your carburator has High and Low Speed jets , they are hidden under the limitor caps otherwise know by mechanics as welch plugs .This was the model of Zama carb that Stihl used for a very short time back in 2011 . They are alluminium and must be drilled out carefully , then you would require a adjuster tool which is available via the dealer or online . Otherwise you could set the metering lever under the diaphragm a few thousands less to lean out the carb . Less complex solution invest $20.00 bucks on a fully adjustable Walbro Wt-215 carb online . The EPA guru, s do not want homeowners playing with these saws...duh ? Anyhow most Stihl that I tune regularly have a very lean setting requiring adjustment . As for your spark arrester screens get rid of them . Unless you cut within US Forestry areas lol . They will plug and cause overheating , stalling ..etc ! The MS 170 is a consumer , hobby saw not a professional grade unit , thus cheaper grade in many ways but a good saw for the average homeowner . I have ownered and still do 40 yr old Pioneers & new, Dolmar and Stihl and Husky Pro Saws. They are all getting more restrictive to maintain , between EPA Tuning and S**t Ethanol Fuel . I use nothing but Amsoil Sabre now rated for 50:1 to 100:1 oil Ratios , I never find carbon within my cylinder heads or spark plugs . However I will not bad mouth Opti 2 or Stihl Ultra when used properly . Anyhow if you can't figure the carb out just bring to a area small engine mechanic worth his reputation who will tune your carb properly , Hell with the Stihl Dealer Bullshit . If it was in my shop it would have been out the door within the hour ripping wood chips the size of nickles ! P.S. Nothing wrong with the Old Homelites of the 60's before Poulan bought them out lol .
#29
C
chzuck
Sure wish you could post a photo of exactly where those welch plugs are. Since I cleaned the sceen my saw is ripping wood chips the size of nickles.
C
chzuck
Ok let me say this again , your carburator has High and Low Speed jets , they are hidden under the limitor caps otherwise know by mechanics as welch plugs .This was the model of Zama carb that Stihl used for a very short time back in 2011 . They are alluminium and must be drilled out carefully , then you would require a adjuster tool which is available via the dealer or online . Otherwise you could set the metering lever under the diaphragm a few thousands less to lean out the carb . Less complex solution invest $20.00 bucks on a fully adjustable Walbro Wt-215 carb online . The EPA guru, s do not want homeowners playing with these saws...duh ? Anyhow most Stihl that I tune regularly have a very lean setting requiring adjustment . As for your spark arrester screens get rid of them . Unless you cut within US Forestry areas lol . They will plug and cause overheating , stalling ..etc ! The MS 170 is a consumer , hobby saw not a professional grade unit , thus cheaper grade in many ways but a good saw for the average homeowner . I have ownered and still do 40 yr old Pioneers & new, Dolmar and Stihl and Husky Pro Saws. They are all getting more restrictive to maintain , between EPA Tuning and S**t Ethanol Fuel . I use nothing but Amsoil Sabre now rated for 50:1 to 100:1 oil Ratios , I never find carbon within my cylinder heads or spark plugs . However I will not bad mouth Opti 2 or Stihl Ultra when used properly . Anyhow if you can't figure the carb out just bring to a area small engine mechanic worth his reputation who will tune your carb properly , Hell with the Stihl Dealer Bullshit . If it was in my shop it would have been out the door within the hour ripping wood chips the size of nickles ! P.S. Nothing wrong with the Old Homelites of the 60's before Poulan bought them out lol .
Sure wish you could post a photo of exactly where those welch plugs are. Since I cleaned the sceen my saw is ripping wood chips the size of nickles.
#30
T
Tyy
T
Tyy
Hey , just got back from my Brotherinlaws , he was repairing a Stihl 017 (former MS 170) he installed a new Quankun carb fully adjustable from Amazon for $12.99 with 6 day delivery . So there you go no drilling or welch plug replacement and gluing required.
P.S. as for the location of welch plugs would be within the two holes you reported under the idle adjusting screw location . I would strongly suggest you remove the mesh exhaust screen once you replace the carb , you will notice significant power increase and fuel conservation . All the best , drop me a line if require tuning advice !
P.S. as for the location of welch plugs would be within the two holes you reported under the idle adjusting screw location . I would strongly suggest you remove the mesh exhaust screen once you replace the carb , you will notice significant power increase and fuel conservation . All the best , drop me a line if require tuning advice !
#31
C
chzuck
C
chzuck
Sorry to say, but those two holes are blank holes with no welch caps. There is an L & H in the casting at those holes. After your email, I removed the air box and took a good look and there just are not any plugs in those holes on my saw. Purchased it in July 2012. Right now the saw is running great. If it ain't broke, don't fix it.
#32
stevestd
I had a similar problem with both a Shindaiwa brush cutter and hedge trimmer about 8 years ago (both with the same engine). I removed the spark arrester, but the exhaust was also blocked/restricted which caused all sorts of problems such as engine difficult to start, ran rough and low on power. Cleaned the exhaust, stopped using ethanol fuel and replaced it with Shell V-Power 98 octane. Have not had one problem since.
stevestd
Ok let me say this again , your carburator has High and Low Speed jets , they are hidden under the limitor caps otherwise know by mechanics as welch plugs .This was the model of Zama carb that Stihl used for a very short time back in 2011 . They are alluminium and must be drilled out carefully , then you would require a adjuster tool which is available via the dealer or online . Otherwise you could set the metering lever under the diaphragm a few thousands less to lean out the carb . Less complex solution invest $20.00 bucks on a fully adjustable Walbro Wt-215 carb online . The EPA guru, s do not want homeowners playing with these saws...duh ? Anyhow most Stihl that I tune regularly have a very lean setting requiring adjustment . As for your spark arrester screens get rid of them . Unless you cut within US Forestry areas lol . They will plug and cause overheating , stalling ..etc ! The MS 170 is a consumer , hobby saw not a professional grade unit , thus cheaper grade in many ways but a good saw for the average homeowner . I have ownered and still do 40 yr old Pioneers & new, Dolmar and Stihl and Husky Pro Saws. They are all getting more restrictive to maintain , between EPA Tuning and S**t Ethanol Fuel . I use nothing but Amsoil Sabre now rated for 50:1 to 100:1 oil Ratios , I never find carbon within my cylinder heads or spark plugs . However I will not bad mouth Opti 2 or Stihl Ultra when used properly . Anyhow if you can't figure the carb out just bring to a area small engine mechanic worth his reputation who will tune your carb properly , Hell with the Stihl Dealer Bullshit . If it was in my shop it would have been out the door within the hour ripping wood chips the size of nickles ! P.S. Nothing wrong with the Old Homelites of the 60's before Poulan bought them out lol .
I had a similar problem with both a Shindaiwa brush cutter and hedge trimmer about 8 years ago (both with the same engine). I removed the spark arrester, but the exhaust was also blocked/restricted which caused all sorts of problems such as engine difficult to start, ran rough and low on power. Cleaned the exhaust, stopped using ethanol fuel and replaced it with Shell V-Power 98 octane. Have not had one problem since.
#33
T
Tyy
T
Tyy
Ethanol fuel will not cause exhaust system blockage , excessive oil or over rich fuel mixture only causes that condition . Ethanol will however cause all kinds of carburation restrictions with these small engine units . If you use premium grade synthetic oils Amsoil ..etc they have fuel conditioner within the oil which protects the fuel from water entrainment and separation during storage . Otherwise , some form of fuel treatment is required , such as within small engine 4 cycle units . Some people like Stabile or Seafoam , I utilize Startron fuel conditioner when ever I must use Ethanol fuel in 4 cycle engines , good for 2 yrs of fuel storage . As for the Stihl 170 still have not heard the condition of the spark plug colouration . I agree if units is running fine now don't mess with it if it returns to previous condition you know a easy solution . I believe the carb is one of the chineese clone carbs that Stihl used for a quick epa compliance with fixed jets which ran rich from the factory during break in and stayed that way , causing the required screen cleaning or removal , do to excessive carbon fouling from the over rich condition .
#34
B
bertsmobile1
B
bertsmobile1
FWIW, I have been swapping out these cast in fixed jet carbs with older adjustable ones.
Ryobi has been using non adjustable carbs for decades down here.
I inherited a truck load of "dead" lawn hornets with the business.
An old bloke from the local mens shed put me onto this and since then I have offloaded around 100 trimmers.
The fixed idle circuit blocks up so they get hard to start .
New carbs are way too expensive and you need to get exactly the right one but with an adjustable carb the only worry is to get a carb for the same size engine or slightly bigger and I also inherited a 5 gallon drum full of old carbs ( Bert never threw anything out ).
So I would be inclined to try that with your chainsaw.
Also wash it out before you start.
Blue smoke oils work by coming out of solution under pressure ( much like squeezing water out of a sponge ) and condensing in the sump.
The bearings only require a drop or two of oil and I have found some with several ounces of oil in & under the bearings.
Back in the "old" days blue smokers were fitted with draining plugs to facititate draining the engine oil which never mixed properly with the gas .
Now fitting an adjustable "non EPA complient " carb is most likely illegal so you do it at your own risk.
Other than that just keep in reducing the oil till the screen stops clogging.
I run my lawnmowers at 50:1 using Stens oil in place of 25:1 with absolutely no problems lubrication wise.
The same 50:1 goes in my Stihl gear against the 40:1 recommended mix, again no problems.
Now if the gear was run 8 hours/ day continious in death valley it might overheat, but I take the care to keep my cooling fins & crankcases clean.
Ryobi has been using non adjustable carbs for decades down here.
I inherited a truck load of "dead" lawn hornets with the business.
An old bloke from the local mens shed put me onto this and since then I have offloaded around 100 trimmers.
The fixed idle circuit blocks up so they get hard to start .
New carbs are way too expensive and you need to get exactly the right one but with an adjustable carb the only worry is to get a carb for the same size engine or slightly bigger and I also inherited a 5 gallon drum full of old carbs ( Bert never threw anything out ).
So I would be inclined to try that with your chainsaw.
Also wash it out before you start.
Blue smoke oils work by coming out of solution under pressure ( much like squeezing water out of a sponge ) and condensing in the sump.
The bearings only require a drop or two of oil and I have found some with several ounces of oil in & under the bearings.
Back in the "old" days blue smokers were fitted with draining plugs to facititate draining the engine oil which never mixed properly with the gas .
Now fitting an adjustable "non EPA complient " carb is most likely illegal so you do it at your own risk.
Other than that just keep in reducing the oil till the screen stops clogging.
I run my lawnmowers at 50:1 using Stens oil in place of 25:1 with absolutely no problems lubrication wise.
The same 50:1 goes in my Stihl gear against the 40:1 recommended mix, again no problems.
Now if the gear was run 8 hours/ day continious in death valley it might overheat, but I take the care to keep my cooling fins & crankcases clean.
#35
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Bert , I currently have both a MS 260 and a MS 361 both early 2000 vintage , both Pro Grade , unfortunately the newer 361 much like the current 261 are epa lean fully adjustable carbs . I had to remove the welch plugs and actually rejet the 361 . I have also rejetted every Echo product that has came in the door due to the high elevations here . Unfortunately Stihl moved from Keihien carbs to Zama's in the 90's , not bad carbs until the epa regs came out . Today most carbs are Chineese Clones junk but cheap to replace . I remember back when we used Sae. 30 for premix @ 16:1 on the Old Macs and Pioneers lol . Lots of Carbon fouling back then and routine Head and Cylinder decarbonizing one or twice a yr . Also all my saws have muffler screens removed , since only cut within private property , better chance of having the MNR show up during Kangaro Season then finding me cutting fire wood up here in the Great White North !
#36
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startrite
Sounds like the carburetor is running too rich. Unfortunately the carburetor on your saw is non-adjustable. The good news is you can buy a new one on eBay for around $15.00. Since the saw is out of warranty, I would use Amsoil Saber mixed at 80 to 1. I have a Stihl MS291 and use this oil at the 80 to 1 ratio and use this same mix with all of my 2-stroke equipment regardless of the manufacturers mix requirements. Amsoil claims that Amsoil Saber can be mixed all the way up to 100 to 1 and still have plenty of wear protection. I wasn't willing to go that far with it but I have yet to replace the spark plug or clean the spark arrester on any of them. They all run cleaner with little or no smoke and seem to have more power without any carbon buildup. Hope this helps.
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startrite
Well, it is not brand new and under warranty anymore. I bought it in 2012.
I emailed Stihl about the issue and below is their reply.
Two stroke engines like the one in your MS170 use an ignition principle called "loop scavenging". This means that when the fuel is cycled through the four transfer ports of the cylinder from the bottom to the top of the combustion chamber, it begins to swirl in a widespread pattern to insure that as much of the fuel burns as possible when the unit fires the ignition spark.
Unfortunately, it doesn't matter how efficient the design of the engine is in the two-cycle format because a small amount of raw fuel is going to escape with the burnt exhaust gasses each time the engine fires. This raw gas/oil mix tends to collect on the fire arrestor screen of the muffler, and over time it will accumulate and cause an obstruction. When this happens, the obstruction will not allow the exhaust gasses to escape, causing them instead to bounce off and push back through the combustion chamber and, if the blockage is severe enough, out of the carburetor venturi onto the air filter.
The issue can be compounded if the engine is feathered or run at part throttle for extended periods of time. The fuel cannot burn efficiently when the engine is run in this manner, so the screen can clog much faster.
The best way to cure this problem, as you know, is to remove the screen from the muffler and check it for carbon build-up. If carbon is present, simply pass a wire brush over the screen from all sides until the debris is removed. Then re-install it back into the muffler and try your starting procedures once more.
I think I may try another brand oil when the Stihl Ultra is gone. Not sure if my Tanaka string trimmer has a screen, but I have had that for almost 20 years and have never had that kind of problem and it runs 25:1 mix. And I could remove the screen. None of my other, vintage saws have that fine of a screen and I only cut wood on my property with my saws.
Sounds like the carburetor is running too rich. Unfortunately the carburetor on your saw is non-adjustable. The good news is you can buy a new one on eBay for around $15.00. Since the saw is out of warranty, I would use Amsoil Saber mixed at 80 to 1. I have a Stihl MS291 and use this oil at the 80 to 1 ratio and use this same mix with all of my 2-stroke equipment regardless of the manufacturers mix requirements. Amsoil claims that Amsoil Saber can be mixed all the way up to 100 to 1 and still have plenty of wear protection. I wasn't willing to go that far with it but I have yet to replace the spark plug or clean the spark arrester on any of them. They all run cleaner with little or no smoke and seem to have more power without any carbon buildup. Hope this helps.
#37
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Fully adjustable carbs available at half that price , Amsoil in my opinion is the very Best Oil for all 2-stroke applications designed to be used between 50-100:1 Ratio,s!
T
Tyy
Sounds like the carburetor is running too rich. Unfortunately the carburetor on your saw is non-adjustable. The good news is you can buy a new one on eBay for around $15.00. Since the saw is out of warranty, I would use Amsoil Saber mixed at 80 to 1. I have a Stihl MS291 and use this oil at the 80 to 1 ratio and use this same mix with all of my 2-stroke equipment regardless of the manufacturers mix requirements. Amsoil claims that Amsoil Saber can be mixed all the way up to 100 to 1 and still have plenty of wear protection. I wasn't willing to go that far with it but I have yet to replace the spark plug or clean the spark arrester on any of them. They all run cleaner with little or no smoke and seem to have more power without any carbon buildup. Hope this helps.
Fully adjustable carbs available at half that price , Amsoil in my opinion is the very Best Oil for all 2-stroke applications designed to be used between 50-100:1 Ratio,s!