I have a stihl BT 121 Auger it has made me a boatload of money. It has a lot of hrs on it and has begun giving me 1 issue, flooding no matter what I do it is extremely hard to start. So I decided to put a new carburetor on it, it no longer floods but it is still hard to start. My questions are could this be a compression issue or a valve issue? is a rebuild in order? When it runs it runs very well but when it don't aint nothing gonna get her going. I have literally taken the pull cord cover off put a 1/2" socket attached to an impact gun just to get it to start and run. Does anyone have any suggestion on what I should do next?
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Stihl BT121 AUGER
- Thread starter eric331
- Start date
bertsmobile1
Lawn Royalty
Sounds very much like crankcase seals, Classic symptoms, impossible to start when left standing for a long while then once started runs very well.
And the flooding most likely caused one of the seals to pop.
So it is time to visit a workshop or do an all day repair for a 1st time DIY.
However you can really only confirm seals by doing a pressure & vacuum test on the engine.
To do this on a Stihl you need some special tools and blanking plates.
Go to You tube.
Search Crankcase pressure testing.
The upload for Joe Pace ( ex-Husqvarna dealer service school ) is the best one.
Before you start, pull the muffler and look at the piston.
If it has deep scratches that go right across the rings then the barrel & piston is also toast.
Blown seals cause lean running.
On a chain saw or brush cutter the operator notices the lack of balls but on an auger with the big reduction gearing it is no where near as obvious.
And the flooding most likely caused one of the seals to pop.
So it is time to visit a workshop or do an all day repair for a 1st time DIY.
However you can really only confirm seals by doing a pressure & vacuum test on the engine.
To do this on a Stihl you need some special tools and blanking plates.
Go to You tube.
Search Crankcase pressure testing.
The upload for Joe Pace ( ex-Husqvarna dealer service school ) is the best one.
Before you start, pull the muffler and look at the piston.
If it has deep scratches that go right across the rings then the barrel & piston is also toast.
Blown seals cause lean running.
On a chain saw or brush cutter the operator notices the lack of balls but on an auger with the big reduction gearing it is no where near as obvious.
Sounds very much like crankcase seals, Classic symptoms, impossible to start when left standing for a long while then once started runs very well.
And the flooding most likely caused one of the seals to pop.
So it is time to visit a workshop or do an all day repair for a 1st time DIY.
However you can really only confirm seals by doing a pressure & vacuum test on the engine.
To do this on a Stihl you need some special tools and blanking plates.
Go to You tube.
Search Crankcase pressure testing.
The upload for Joe Pace ( ex-Husqvarna dealer service school ) is the best one.
Before you start, pull the muffler and look at the piston.
If it has deep scratches that go right across the rings then the barrel & piston is also toast.
Blown seals cause lean running.
On a chain saw or brush cutter the operator notices the lack of balls but on an auger with the big reduction gearing it is no where near as obvious.
Well that sucks I guess its off to the shop any guess ballpark on cost?
bertsmobile1
Lawn Royalty
Well that sucks I guess its off to the shop any guess ballpark on cost?
I charge out scheduled rates ( warranty work ) and seals is 2.0 hours ( at whatever they charge ) + parts.
A small workshop ( without a massive glass fronted showroom ) will generally charge less than a franchise dealer cause they are free to use after market parts.
You know how it goes, Oregon gasket $ 1.50 Stihl gasket $ 4.95 ( same gasket different packaging ).
Pull the muffler off first and check the piston.
Do not tell the workshop you suspect the seals, let them do their diagnosis.
I have just finished doing an 034 that I was told the seals needed replacing so I replaced the seals.
The real problem was a leaking impulse line which caused the crank to fail pressure testing.
So a $ 50 job became a $ 200 job because I trusted the diagnosis of the Stihl Shop who told the owner than it needed new seals and that the seals are NLA.
And the NLA bit is true, Stihl no longer list the seals . The Stihl shop can not fit after market seals because it contraviens their franchise arangement where as I can fit freely available std seals.
I charge out scheduled rates ( warranty work ) and seals is 2.0 hours ( at whatever they charge ) + parts.
A small workshop ( without a massive glass fronted showroom ) will generally charge less than a franchise dealer cause they are free to use after market parts.
You know how it goes, Oregon gasket $ 1.50 Stihl gasket $ 4.95 ( same gasket different packaging ).
Pull the muffler off first and check the piston.
Do not tell the workshop you suspect the seals, let them do their diagnosis.
I have just finished doing an 034 that I was told the seals needed replacing so I replaced the seals.
The real problem was a leaking impulse line which caused the crank to fail pressure testing.
So a $ 50 job became a $ 200 job because I trusted the diagnosis of the Stihl Shop who told the owner than it needed new seals and that the seals are NLA.
And the NLA bit is true, Stihl no longer list the seals . The Stihl shop can not fit after market seals because it contraviens their franchise arangement where as I can fit freely available std seals.
Oh wait for a min the impulse line you are speaking of the fitting you are speaking of fits loosely on the new aftermarket because of a smooth type pipe on the aftermarket but I believe the OEM carb had a plastic barb type fitting which made it difficult to remove that impulse line. Do you see where I am going. I am just not sure from memory what I can do (Its 6am sunday) but I am also sure it was pretty loosely fitted. I am going to pull the muffler and check the piston as instructed but I am also going to figure out this impulse line and get back to you, cause if a leak can cause this I am also certaing there could be a leak there
bertsmobile1
Lawn Royalty
On your engine the impulse feed goes through the carb manifold then into the fuel pump in the carb.
It was an illustrative example .
On your engine you a fuel line and a return line.
The fuel supply line has thicker walls and goes on the barbed fitting.
The smooth fitting is the return line and is generally a smaller diameter tubing.
Diagnosing small 2 stroke hand helds over the web is near impossible, in fact it is hard enough when you have them in your hands.
Right now I have a K970 saw that has been in the shop for 5 months which is busting my balls and I have that, on the bench, pressure testers , compression testers , ignition analyser, even popped it on the silly scope to check the wave forms of the spark and I still can not get it to run properly so don't expect any one to work miracles on line.
Your engine is a vertically split one so the seals should just push in from either side.
However without seeing , hearing, feeling & smelling it working out what is wrong is a little difficult.
When the magnets in the flywheel get weak or the insulation on the ignition coil breaks down they can be a bugger to start as well as you don't get enough spark to fire at cranking speeds.
You did not give us much to work with but from what you stated, seals or impulse line would be the most likely.
You could check that the 2 bolts holding the carb in are tight cause they will cause it to run lean as well & be a bugger to start .
It was an illustrative example .
On your engine you a fuel line and a return line.
The fuel supply line has thicker walls and goes on the barbed fitting.
The smooth fitting is the return line and is generally a smaller diameter tubing.
Diagnosing small 2 stroke hand helds over the web is near impossible, in fact it is hard enough when you have them in your hands.
Right now I have a K970 saw that has been in the shop for 5 months which is busting my balls and I have that, on the bench, pressure testers , compression testers , ignition analyser, even popped it on the silly scope to check the wave forms of the spark and I still can not get it to run properly so don't expect any one to work miracles on line.
Your engine is a vertically split one so the seals should just push in from either side.
However without seeing , hearing, feeling & smelling it working out what is wrong is a little difficult.
When the magnets in the flywheel get weak or the insulation on the ignition coil breaks down they can be a bugger to start as well as you don't get enough spark to fire at cranking speeds.
You did not give us much to work with but from what you stated, seals or impulse line would be the most likely.
You could check that the 2 bolts holding the carb in are tight cause they will cause it to run lean as well & be a bugger to start .
On your engine the impulse feed goes through the carb manifold then into the fuel pump in the carb.
It was an illustrative example .
On your engine you a fuel line and a return line.
The fuel supply line has thicker walls and goes on the barbed fitting.
The smooth fitting is the return line and is generally a smaller diameter tubing.
Diagnosing small 2 stroke hand helds over the web is near impossible, in fact it is hard enough when you have them in your hands.
Right now I have a K970 saw that has been in the shop for 5 months which is busting my balls and I have that, on the bench, pressure testers , compression testers , ignition analyser, even popped it on the silly scope to check the wave forms of the spark and I still can not get it to run properly so don't expect any one to work miracles on line.
Your engine is a vertically split one so the seals should just push in from either side.
However without seeing , hearing, feeling & smelling it working out what is wrong is a little difficult.
When the magnets in the flywheel get weak or the insulation on the ignition coil breaks down they can be a bugger to start as well as you don't get enough spark to fire at cranking speeds.
You did not give us much to work with but from what you stated, seals or impulse line would be the most likely.
You could check that the 2 bolts holding the carb in are tight cause they will cause it to run lean as well & be a bugger to start .
First off let me thank you for the fresh perspective I never exspected a magic cure over the internet but what you said made me think 1) about the new after market carb I had to change the arm where the throttle cable connects because the end of the cable wouldn't slide all the way down into the aftermarket so I took the one off the OEM problem solved. The other was the barbed fitting on the OEM, the aftermarket did not have it only a smooth brass tube my guess if there's an air leak in addition to one at the seals then it would be here as the impulse line went on to easy not to leak a little. So my next step is to take the muffler off and inspect what I can see of the Piston. then put it all back together and take it to the shop and see what they can tell me. I just need to figure at what price point do I say enough is enough and just buy a new one $700. I truly want to get it fixed but I worry about it being a permanent fix
bertsmobile1
Lawn Royalty
The price point is of course up to you.
Just because something is advertised as OEM dose not mean it is ;-
1) the correct part
2) a quality part.
Most of this stiff comes out of 3rd world countries cause 1st world countries will not pay a fair price for consumer durables.
In mos cases the factories making them have no idea what the part fits, they have a set of drawings and usually a sample + and order from, say Stihl.
margins are very thin so when the QC team at Stihl reject a batch for whatever reason the factory on sells them to some one else, who sells them to some one else and finally they end up on Evilpay or Amazon.
Advertised as OEM which is quite truthful they just omit to note they are OEM rejects.
A factory could make 50 or more variations of exactly the same carb with the only difference being the ends of the throttle & choke controls.
Looks like you got one of them.
It could very well fit the 120 powerhead used on a different tool.
Just because something is advertised as OEM dose not mean it is ;-
1) the correct part
2) a quality part.
Most of this stiff comes out of 3rd world countries cause 1st world countries will not pay a fair price for consumer durables.
In mos cases the factories making them have no idea what the part fits, they have a set of drawings and usually a sample + and order from, say Stihl.
margins are very thin so when the QC team at Stihl reject a batch for whatever reason the factory on sells them to some one else, who sells them to some one else and finally they end up on Evilpay or Amazon.
Advertised as OEM which is quite truthful they just omit to note they are OEM rejects.
A factory could make 50 or more variations of exactly the same carb with the only difference being the ends of the throttle & choke controls.
Looks like you got one of them.
It could very well fit the 120 powerhead used on a different tool.