Stihl MS180C bogs down

[NeilH]

I've got a Stihl MS180C that will run like it should for a few minutes and then wants to bog down when the trigger is pressed. Doesn't happen everytime. Sometimes I can let it cool down for 1/2 hr or so and then start it back up and it works fine. Sometimes will start and immediately bogs down. Doesn't seem to be any rhyme or reason to it's behavior. I've had the carb off and cleaned it all up. Didn't put in a carb kit as the saw is only about 3 yrs old and the gaskets and diaphrams seem flexible and look great. Cleaned the screen, took out the needle valve etc and everything looks clean. Blew carb cleaner through the holes etc. I didn't touch the jets. I've done this 3 or 4 times and it always looks clean before I tear it apart. Always works fine for a time or two after doing all that. I can do this in my sleep!!

Is it time for a carb kit or is there something I'm missing? Filter is clean (fuel and air). Always starts like it should. Should I be looking at the jets?

Thanks in advance for any suggestions.
Neil

 

[Vintage Engine Repairs]

Bogging is a lean symptom, not enough fuel or too much air.
I’d suggest it’s as simple as needing a very basic service (fuel line, filter and carb kit). What you think is good could be fine on an adjustable carb where you can give it more fuel, but on an already lean set, non adjustable carb, the window for operation is tiny.

3 years on the original kit may not seem like much, but it takes very little to upset the ideal fuel mix. Do it, go oem parts and see.

Also, how good old your fuel?

 

[ZeroJunk]

That series of saws after they went to the non adjustable carb has to be the sorriest POS that any chainsaw manufacturer ever created.

 

[cookies]

There is a single air/fuel ratio screw on those carbs. In my experience the fuel pump flap diaphragm deforms creating a lean bog. I looked at a ms170 on wednesday that had the same issues and it was claimed to be 2 years old and only used to cut 3 trees up last year then put away.

 

[Oletrapper]

That series of saws after they went to the non adjustable carb has to be the sorriest POS that any chainsaw manufacturer ever created.

You can blame the tree huggers and the EPA for that and not the manufacturer. jmho OT

 

[Oletrapper]

Bogging is a lean symptom, not enough fuel or too much air.
I’d suggest it’s as simple as needing a very basic service (fuel line, filter and carb kit). What you think is good could be fine on an adjustable carb where you can give it more fuel, but on an already lean set, non adjustable carb, the window for operation is tiny.

3 years on the original kit may not seem like much, but it takes very little to upset the ideal fuel mix. Do it, go oem parts and see.

Also, how good old your fuel?

Here in the US, Ethanol fuel absolutely kills carbs on small engines. Get the oem parts as suggested and compare the new metering diaphragm with the one in it now. You will see the difference in how supple/soft the new one is compared to yours. OT

 

[stihltech]

Did you check the vent? As in apply vacuum to the tank and make sure it does not hold?

 

[cookies]

You can blame the tree huggers and the EPA for that and not the manufacturer. jmho OT

These saws are by design/price aimed at people that only have the ability to add fluids, run it and then be thrown away when cost to repair is half what a new one costs which seems to be figured right at a carb/fuelfilter/chain replacement at the dealer.

 

[GenXer]

I have an 017 that I got for free, it did the same thing. I put a cheap carb from farmertec.com on it and now works like it should. Muffler mod and now both the H&L adjustment on the carb, 20 dollar fix.

 

[a. palmer jr.]

Yeah, I was about to say that. I put a cheapo fully adjustable carb. on all the small Stihls I get in and it really helps. You may have to modify the air box a little to accommodate the screws but it's worth it..

 

[Captain Bruce]

I've got a Stihl MS180C that will run like it should for a few minutes and then wants to bog down when the trigger is pressed. Doesn't happen everytime. Sometimes I can let it cool down for 1/2 hr or so and then start it back up and it works fine. Sometimes will start and immediately bogs down. Doesn't seem to be any rhyme or reason to it's behavior. I've had the carb off and cleaned it all up. Didn't put in a carb kit as the saw is only about 3 yrs old and the gaskets and diaphrams seem flexible and look great. Cleaned the screen, took out the needle valve etc and everything looks clean. Blew carb cleaner through the holes etc. I didn't touch the jets. I've done this 3 or 4 times and it always looks clean before I tear it apart. Always works fine for a time or two after doing all that. I can do this in my sleep!!

Is it time for a carb kit or is there something I'm missing? Filter is clean (fuel and air). Always starts like it should. Should I be looking at the jets?

Thanks in advance for any suggestions.
Neil

Buy/install a $20 carb, and start the saw. If the problem is solved, toss the old carb, that you "think" is okay, and go back to trimming small branches......

 

[NeilH]

Buy/install a $20 carb, and start the saw. If the problem is solved, toss the old carb, that you "think" is okay, and go back to trimming small branches......

After I wrote the original post, I read it and came to the same decision!! LOL!!

 

[NeilH]

Bogging is a lean symptom, not enough fuel or too much air.
I’d suggest it’s as simple as needing a very basic service (fuel line, filter and carb kit). What you think is good could be fine on an adjustable carb where you can give it more fuel, but on an already lean set, non adjustable carb, the window for operation is tiny.

3 years on the original kit may not seem like much, but it takes very little to upset the ideal fuel mix. Do it, go oem parts and see.

Also, how good old your fuel?

Thanks for the suggestions. Fuel is new and non ethanol. Hurst me to say that, I'm a corn farmer, but I do accept how it can affect small engines.

 

[chipper1]

Thanks for the suggestions. Fuel is new and non ethanol. Hurst me to say that, I'm a corn farmer, but I do accept how it can affect small engines.

At least you're not a con farmer like Billy Gates. Sounds like his purchase of all that land is sure to make him more money now that they are wanting to push the ethanal minimum in road fuel up to 15% .

Get the new carb and you should be off to the races, but be sure to take a good look at the fuel and impulse lines first.
Thanks for all your hard work .

 

[Old2stroke]

An intermittent problem like you are describing is often due to a faulty nozzle check valve that likes to stick open. The critical part in the valve is a small rubbery round disc that gets distorted by alcohol in the fuel and sometimes just old age. Unfortunately, repair kits never include them and carb replacement is often the solution.

 

[ZeroJunk]

We buy OEM carburetors for these saws about 20 at a time. I can change one in a couple of minutes. I suppose I could put an adjustable carb on one and drill holes in the air box, but since these are customer saws who I never even see I can't really get in to that.
Plus, I have tried the adjustable carbs on some saws farmers bring to the house and getting the holes to line up in such a way that somebody down the road could easily put a screw driver on the needle was an issue since the top handle and the air box isn't really made for it to line up.