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jeepwm69

Chainsaw carbs.....

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I consider myself pretty good with carb'd engines.  Not like there's anything real complicated about them, but these tiny carbs are giving me fits.

 

A friend gave me a Stihl MS180C, which from what I can determine, is considered a pile of crud homeowner grade saw.  Still though, it was free, so being the junker that I am, I took it.  He loaned it out, and it was run with the brake on, which melted the right side of the case and smoked the clutch.  Said it ran when he gave it to me, but needed the case replaced and he's not a DIY guy so wasn't worth paying the dealer to fix it vs buying another saw.

 

I ordered a replacement case and clutch from Huztl, which was pretty straightforward and the saw went back together without much trouble.  The tag from the repair estimate on it said 2015, so looks like it's been sitting for 4-5 years.   I took the carb apart, soaked it in Berryman's, blew out all the orifices, and put it back together.  The gaskets were pretty dried out looking, and I needed a new fuel line too, so I ordered a tune-up kit off of ebay that consisted of a replacement oil pump, oil line, fuel line, air filter, and carb, figuring I could use the fuel line and the rest would be spares.

 

Got it together early this morning.  Wouldn't fire off.  Shot of starter fluid, and it fired off till the fluid burned off.  Took carb back off, everything inside the carb still looked dry (no fuel).  Blew a shot of air into the fuel line to make sure it was clear, and fuel came back out from the pressure in the tank, so put carb back on.  Same thing.  Took carb back off, tried the ebay carb.  At this point the saw fired off and ran, but was idled WAY up, and when I hit the throttle it bogged down.  Took ebay carb back off, took gaskets and diaphram out of that one, put them in the original Zama/Stihl carb.  Nothing.  Not even a burp.  Took the stuff back off, put it back on the ebay carb, and reinstalled.  Nothing.  So at this point I have two carbs, and neither of them will even get this saw to burp at me.  It will fire off on starter fluid, so it's a fuel delivery problem.  The small jet in the body of the carb is clear.

 

I also had the exact same problem on Dad's old Homelite XL.  I messed with it for a bit, and then put it back up when I got my 346XP and haven't brought it back out to try again on it, but it pretty much did the same thing as this MS180.

 

There is a rubber boot/intake manifold that goes onto the actual engine, and the carb butts up against that rubber intake manifold, and then the air cleaner on the carb. 

 

These tiny carbs frustrate me!  Is this carb still gunked up or am I missing something?  The passages seem to be clear when I blew it out, and the ebay carb is new, so while I wasn't surprised that the saw didn't run right with it, I am surprised that I couldn't get it to run after putting the ebay carb back on

 

https://www.ebay.com/itm/Carburetor-Carb-for-Stihl-MS170-MS180-017-018-Chainsaw-Air-Filter-Fuel-Oil-Line/322531794697

Edited by retro
Wow! eBay loaded that link to the max!

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My old Poulan 14" is giving me problems,it sat in storage for about 10 years.It starts runs but will not idle when I let off the gas.I ordered a new carb have not installed yet.Also changed fuel lines and primer bulb.Hope to get it running soon.

 

Good Luck with yours.

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1 hour ago, toodeep said:

How good is the compression on it?

Ah crap.  I should have known you were gonna ask that. 

 

No idea.  Not sure where my compression gauge and adapters are either.  Haven't come across them during my shop cleaning.

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1 hour ago, Wheeler said:

Have u set the hi & low?

 

No adjustments on this one other that idle speed.

 

There is a sleeve in the intake manifold, which is pretty much just a little plastic ring.  I noticed it was cracked/ split.  What purpose does that serve?

 

part number 1 on page 8 of this parts list.

 

https://sawzillaparts.com/content/MS180.pdf

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If it’s cracked would it suck air? Looks like some kind of spacer??... I dunno on that one..

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Had a similar issue on a old Troy-Built weed eater once. Took the carb off and disassembled it and cleaned everything in mineral spirits and has worked fine for 2 years and counting. 

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Pull the plug and see if it will "pop" your finger off of the spark plug hole. If it does there should be enough compression to pull the fuel in.

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What about the filter down in the fuel tank? They get gummed up and that will stop your freshly cleaned carb from getting any fuel. Try running it with a bottle of fuel with a hole in the cap and a small line. Would confirm its fuel line filter in tank.

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Nosed around on the arborist forum.  I'd started a thread there back in 2017 about whether or not it was worth it to replace that plastic engine case.

 

Apparently these tiny carbs are pumped by an impulse hose, which in the case of this saw, is inside of that rubber intake boot.  There's a small hole on the engine side of the carb that needs to line up with that impulse hose, and that white spacer sits in the end of the impulse hose.  Some saws apparently have external impulse hoses, but this saw it's made into the boot/intake manifold, so I'm going to pull the carb back off, and see if that hose is clear all the way through.

 

I also ordered a carb kit that included another intake boot with that spacer/sleeve.

 

Just now, SlammedRanger said:

What about the filter down in the fuel tank? They get gummed up and that will stop your freshly cleaned carb from getting any fuel. Try running it with a bottle of fuel with a hole in the cap and a small line. Would confirm its fuel line filter in tank.

Filter is new.  Replaced it and the fuel line since the old fuel line tore when I took the saw apart.

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Odds are you've discovered the reason why it won't pump any fuel into the carb. That impulse line works off the crankcase vacuum & pressure pulses, so if it breaks or loses its seal the fuel pump diaphragm in the bottom of the carb stops working.

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i would like ta know how you solve this problem. fuel lines are not fuel lines anymore. made in china,don't ya know, fuel lines are hard to find made correctly.

if you add lime to the "Coronna-virus'' you are immune. just dont forget the salt...

on a more serious note. check the coil. i could get nothing out of the diagrams. i dont know if i blocked something, just didn't see any number's

 

 

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Since the clutch end of the crank got hot it might have destroyed the crankshaft seal. May not be anything wrong with the carb or the pulse line. If a crank seal blows on a two-stroke motor the crankcase won’t hold pressure, the motor won't start or run.

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Wonder if that might have been the problem?  Impulse line as it was when I removed the engine from the case, and new intake manifold as it should fit on the engine.

 

 

manifold1.jpg

manifold.jpg

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Those look OK to me.

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32 minutes ago, retro said:

Those look OK to me.

 

 

That top pic shows the impulse tube which was smashed flat when I got the crankcase installed in the housing.

 

No wonder I wasn't getting any gas.

 

Got an OEM Stihl oil line today.  The original was looking a little wet and the aftermarket one I had on hand didn't pop into the tank tightly, so I figured it would leak everywhere and I'd have to do it all over again.

 

Have a carb kit on the way, so will put that in the original Stihl carb and hopefully get it to fire up.

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Its likely the impulse line. If the fuel lines needed replacing chances are the impulse line too, I've worked on acouple crap poulan saws that I find at the dump. Same problem every time. Old cracked fuel and impulse lines.

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On 1/30/2020 at 2:50 PM, TRX Student said:

Its likely the impulse line. If the fuel lines needed replacing chances are the impulse line too, I've worked on acouple crap poulan saws that I find at the dump. Same problem every time. Old cracked fuel and impulse lines.

Also just in case anyone hasn't mentioned it sometimes the muffler spark arrestor gets gummed up with carbon crap and doesn't let the saw flow air out the exhaust correctly.... seen it happen before.... but if you got it running again,Good!!!! I've had my share with chainsaws!!!! Also if the diaphragm is kinda hard where the little round metal thingy is then chances are is not good.... good luck!!!!

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impulse line. never heard of it till now. dumber than a box of rocks E is. What is the impulse line?

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14 hours ago, Orville538 said:

Also just in case anyone hasn't mentioned it sometimes the muffler spark arrestor gets gummed up with carbon crap and doesn't let the saw flow air out the exhaust correctly.... seen it happen before.... but if you got it running again,Good!!!! I've had my share with chainsaws!!!! Also if the diaphragm is kinda hard where the little round metal thingy is then chances are is not good.... good luck!!!!

 

Yeah I checked that, and it was clean.  I don't think this thing was used a lot before the borrower melted the case running it with the brake on.

11 hours ago, LedFTed said:

impulse line. never heard of it till now. dumber than a box of rocks E is. What is the impulse line?

Me either, if it makes you feel better. 

 

It's a line from the cylinder to the carb (pictured above, little nipple inside the intake boot) that sucks gas into the carb as the engine rolls over.

 

Got it put back together this morning and it fired off and ran good, and that was with the cheap Ebay carb too! (I ordered a rebuild kit for the original Stihl carb that is coming in the mail today or tomorrow).

 

There's a little plate between the cylinder and carb that I'm guessing is a heat deflector.  It was keeping me from getting the top cover on, and I ran out of time this morning.  Will get that sorted in the morning and get the bar and chain put back on and see how she cuts.

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1 minute ago, jeepwm69 said:

 

Yeah I checked that, and it was clean.  I don't think this thing was used a lot before the borrower melted the case running it with the brake on.

Me either, if it makes you feel better. 

 

It's a line from the cylinder to the carb (pictured above, little nipple inside the intake boot) that sucks gas into the carb as the engine rolls over.

 

Got it put back together this morning and it fired off and ran good, and that was with the cheap Ebay carb too! (I ordered a rebuild kit for the original Stihl carb that is coming in the mail today or tomorrow).

 

There's a little plate between the cylinder and carb that I'm guessing is a heat deflector.  It was keeping me from getting the top cover on, and I ran out of time this morning.  Will get that sorted in the morning and get the bar and chain put back on and see how she cuts.

WIN

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Well it's a cheapy saw, but I have about $60 in it, and that's with me having an extra carb, rebuild kit, air filters, and intake manifold, so hopefully I can keep it going for awhile with the stuff I have on hand.

 

Most importantly, I know my way around it now.

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With what I've experienced, the stihls are worth it, even if they are the smaller ones. The pro husqs are too, but the poulans and cheapy husqs are not. In the end, some times just fixing something is worth it all.

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On 2/3/2020 at 10:26 AM, jeepwm69 said:

 

Yeah I checked that, and it was clean.  I don't think this thing was used a lot before the borrower melted the case running it with the brake on.

Me either, if it makes you feel better. 

 

It's a line from the cylinder to the carb (pictured above, little nipple inside the intake boot) that sucks gas into the carb as the engine rolls over.

 

Got it put back together this morning and it fired off and ran good, and that was with the cheap Ebay carb too! (I ordered a rebuild kit for the original Stihl carb that is coming in the mail today or tomorrow).

 

There's a little plate between the cylinder and carb that I'm guessing is a heat deflector.  It was keeping me from getting the top cover on, and I ran out of time this morning.  Will get that sorted in the morning and get the bar and chain put back on and see how she cuts.

Helps outs sum. i will always fill dumb. when i know everything, i will be dumb.

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