# Stihl 028WB Chain Saw ? Starts but won?t run



## Captainlarry (Feb 14, 2011)

*Stihl 028WB Chain Saw – Starts but won’t run*

Stihl 028WB Chain Saw – Starts but won’t run - “Nozzle Check Valve“? 

Hello,

Can you please help diagnose this problem?

First the problem history:

Been cutting fine for 2 weekends. Then, after 30 minutes throw the chain off. The engine revs high for just a second. I shut down, re-fuel, re-oil, put the chain on. (Same fuel and oil as I’ve been running for weeks.) Saw fires, but won’t run.

I pulled the air filter and it’s a mess. I brush it off and reinstall - same performance. I try to run it without the filter – same performance. I splash fuel in the carburetor throat – runs a few second longer. Remove the plug and check spark – looks strong and blue.

I ordered a Tillotson HU40B carb kit. Replaced meter needle, pivot mechanism, diaphragms, gaskets. Removed/replaced Welch plug and filter screen after a thorough jet cleaning with carb cleaner, but not compressed air, oops. I re-set the H/L screws to factory 1 ¼ settings (I hope I did not crash these into their seats.) I did not mess with brass plug. 

I removed and inspected impulse tube and intake manifold. I can not find any defects, but I have not inspected with specialized leak finding techniques. No giant holes here.

Compression seems OK – same as ever, but I have not measured. Some old dried oil spun radially outward from crank bearings. I’m sure these need attention, but I don’t want to go there if I can help it. Running a new OEM spark plug now.

Reassembled the saw except bar and chain and basically have the same performance. With lots of pulling, fires and runs very slow and rough for a few seconds @ WOT only. A fine mist of fuel sprays out from carburetor throat. Oil/Fuel is coming out of muffler. I tweak the L screw closed some, then open some, also close H screw completely and can’t perceive a change in performance.

I think that covers most everything. Do I need to press-out the brass carburetor plug “Nozzle Check Valve“? Apparently that may influence idle. 

Help?

CaptainLarry


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## Kenskip1 (Feb 15, 2011)

Pull the muffler off and have a look at the piston.Sounds like an air leak,or a lean mixture of some type may have cooked your piston.Just curious, does your gas mix contain ethanol? Ken


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## pioneerguy600 (Feb 15, 2011)

Check/change in tank fuel filter, carb is not getting enough fuel.
Pioneerguy600


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## Fish (Feb 15, 2011)

Ignition......


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## JDNicol (Feb 15, 2011)

Captainlarry said:


> Some old dried oil spun radially outward from crank bearings. I’m sure these need attention, but I don’t want to go there if I can help it.



Please explain. 

+1 on taking the muffler off to check piston for scoring.


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## Captainlarry (Feb 15, 2011)

Thanks for the feedback guys. I’ve read so much of “your” stuff now, I feel like I’m talking with famous folks.

*Ken*, I’ve wanted to pull the muffler wondering if it was clogged and preventing good flow. I’ll pull it. Not sure I’ll be able to positively ID a “cooked piston”. I thought the piston looked OK on the intake manifold side. Yes, our fuel is said to be “up to 10% ethanol.” I did buy fresh “mid-grade” octane fuel for the re-build test.

*Pioneerguy*, I know I changed the fuel line not too long ago. I thought I would have changed the filter then too. I’ll investigate. Pretty sure I can suck good flow through the line…yuck! But you think it sounds lean and I’ve got fuel/oil coming out the muffler? BTW I run 40:1 with aftermarket 2 stroke oil.

*Fish*, Yeah, I’ve questioned ignition too. Ignition timing in particular. It seems to have good blue spark every time I check it. I could not make sense of the timing marks. Looks like the lines match up just ahead of TDC which makes sense. But the marks could have also been set to line-up right at TDC. My fear was the sudden acceleration after throwing the chain sheared the key partly. Seems like a far fetched theory. I’ll just remove the nut and see if the groves line-up. Otherwise I have not pulled the F/W or changed the points to electronic.

*Jonathan*, What I mean by “old dried oil” is that I figure I have some leaking of the old crank seals, don’t we all? I figured oil would migrate out from the seals and move radially with the air off the flywheel, no? I just did not want to do the work of changing these seals if I can avoid it.

I’m really surprised none of you guys chimed in on the “nozzle check valve” theory. What is that crazy thing supposed to do?

I did more research on AS last night and I realized I put the gasket on the wrong side of the metering diaphragm. I did not expect it to be different from the pump side. I also need to verify the height of the meter pivot mechanism (“inlet control lever”) tonight. These could influence fuel flow, which I’ve been suspecting is too rich right now.

Larry


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## Fish (Feb 15, 2011)

Yes, by all means rule out the fuel system. But don't screw up your carb in the process. Make sure there is no debris under the needle and it is sealing good,
and make sure that passage is clear.

But otherwise, I think the trouble is ignition related.


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## JDNicol (Feb 15, 2011)

You say that if you splash fuel down the carb it will run for a second longer than under normal starting conditions? This to me would imply it is not flooding/way rich.
I am assuming you have tried starting again having corrected the diaphragm/gasket order.

I would still be pulling the muffler, trust me you will know if it is fried or not. I have experienced your described symptoms before on saws that have scored pistons, often rings are held in by aluminium meaning charge can escape back down cylinder.They will fire but not run, if you dump fuel in carb they run for a few seconds on fast idle then die. 
Is the saw hard to get to fire or does it take roughly the same number of pulls as normal?

As for the crank seals, are you sure oil is leaking from them and not elsewhere?


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## Captainlarry (Feb 15, 2011)

Jonathan,

Yes, I understand your thinking that it is not rich because of my splashing fuel trick. I'll fix the gasket order tonight and try it again.

I'll pull the muffler too, if the bolts come free easy enough.

No, I'm not certain about the oil leaks. Maybe bar oil is finding it's way around. Right now I'm just looking to see the saw run.

Larry


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## Kenskip1 (Feb 15, 2011)

*028*

Larry, I also own a 028, and it is a great running saw. Oh buy the way,Welcome to the site!Many individuals here that will help you.They love pictures! Ken


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## Captainlarry (Feb 15, 2011)

Ok, I ruled out some things, I think.

(1) I switched the gasket/main diaphragm order and (2) set the inlet control lever so it is flush with the diaphragm floor. It was pretty high, so I bent it down a tad. A high lever would mean a rich setting, right? So it should be more lean now. I think that I see less (none) raw fuel coming out of the muffler now too.

(3) I pulled the muffler and had a 2-stroke dirt biker friend look at the piston. He thinks it looks fine. The rings move freely up/down. (4) He also confirmed I was getting good compression. (5) The muffler was not restricting flow.

*Fish*, I re-checked spark. (6) I really am getting a good spark with every piston cycle. I know spark changes under comression, but the saw will start pretty reliably - just won't run.

I re-checked fuel flow through the filter...Yuck. There has to be a better way. (7) It flows!

So I ruled out what, 7 things? I could not see if the key was sheared. Almost had the flywheel pulled off using a bicycle crank remover tool. It was the wrong thread pitch. I'll see if my dirt biker friend has a puller that fits.

So the saw will now only start with throttle closed. Runs for a few seconds - dies. If I feather the throttle it "baw-baws" and dies. The H/L screws are at 1 1/4 TO per OEM. Minor tweaks seem to have no influence. Little or no raw fuel at muffler. Fuel still sprays back at me when I open the throttle while pulling.

WHAT NEXT?

Captain Larry:msp_huh:


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## Kenskip1 (Feb 15, 2011)

Larry, I am afraid that you are beating a dead horse.When the saw raced at the beginning of your post, I have good reason to suspect that you may have melted your piston.As an owner of a 028 I find it hard to see the piston from the intake side. Not saying it cannot be done but the muffler side is easier. Now pull the muffler off and put a few drops of oil on the piston. Now slowly pull the rope and watch for bubbles.Your friend with the bikes may have not had a really good look.To cut through the lard and get to the ham get a compression tester or have it tested.I suspect that it will be in the 90-115 lb range.Buy the way, I hope that I am wrong.Ken


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## motoman.5150 (Feb 16, 2011)

I agree with Fish,just had same trouble with mine, electronic conversion, will most likely clear you up for $20 bucks, Atom module at Napa part number 7-01749, switch neg. and positive leads and you don't have to mess with timing, did 2 this week !!!!


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## sefh3 (Feb 16, 2011)

Check the piston to make sure it's not toast. Take a picture and post the rings on the saw. Then check the flywheel key while your at it. If it's shot it throws off the timing of the saw.


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## Captainlarry (Feb 17, 2011)

Yes, We're beating a dead horse.

The piston is fine. I'm not pulling the muffler again. We saw bubbles the first time with the rich mixture oozing down the exaust port. And yes, I did see the piston through a larger window on the intake side after removing the intake mainfold. The rings are floating freely. I'm really sorry I did not take pictures to prove it. I'm not accustomed to photo documenting. 

So, now I'm sounding like a know-it-all snot. Sorry. :msp_sad: Don't mean to. I did what was suggested and my opinion and my very experienced biker friend both think the piston/compression looks fine/typical.

Won't get a chance to work on this until 2-21-11. I need to get this thing running before next weekend's planned cutting day. I'm planning to re-adjust the inlet control lever height because I'm afraid the setting height may need to account for back lash, though Tillotson did not explicitly mention it. The current setting would account for the new lean condition.

*Motoman*, thanks for the Napa lead.

Talk to you Monday.

LArry


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## Captainlarry (Mar 9, 2011)

*Conclusion - Ignition!*

clap:

Hey Guys,

I got the saw running Friday 2-25-11. Fish was right again. It was ignition. I did not understand the power of a powerful spark at the right timing. I knew before I started my thread I should listen close to Fish’s recommendation, if I was lucky enough to get one.
I’m going to post my version of the Electronic Ignition rebuild, though I did see a decent one out there. My version may help answer some of the questions that I still had.

Photo 1
View attachment 175595

Overview of my 20 year old Stihl 028 WB. Ignition system shown bottom-left with flywheel removed. Common flywheel tool 22mm x 1.5mm thread pitch. Thread it in to the threaded hub bore, then turn inner screw inward to POP! flywheel off. Some have said you can leave the flywheel on, and that’s fine, but I had the tool. I just figured I’d remove the friction and heat of the rocker arm, and I figured I could work better having all of the existing wire. 

Photo 2
View attachment 175591

The flywheel is apparently a single magnet although one might look at it and think it had two magnets. I believe I’m seeing two poles of the same magnet. I say all this because the instructions warn that the module does not work with two magnet systems. I further thought that two magnets would equate to two cylinders which the instructions also states as inadvisable. I also included the module instructions and my receipt.

Photo 3
View attachment 175593

The existing points and condenser system. 

Photo 4
ATTACH=CONFIG]175592[/ATTACH]
It’s ok to remove all that was under the flywheel. There is NO need to remove the coil. You may be able to pull the coil wire (yellow-black) and stop wire (black) through the rubber grommet without cutting them, but I cut them first to facilitate back-threading the wire from under the coil. 

Photo 5
View attachment 175594


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## Captainlarry (Mar 28, 2011)

Sorry the pictures did not come through in-line...Here is my final post to document the re-build.

View attachment 177846

Photo 6
I sealed the hole where the wires came through with hot glue (silicone would be better) to keep dirt away from the crank shaft seal.
View attachment 177847

Photo 7
The two wires are pulled out to a convenient location above the coil. I stripped off the insulation to facilitate soldering to the module lead.
View attachment 177848

Photo 8
The completed installation. I had to make a sheet metal bracket to hold the module. I drilled three holes. One for under the existing coil bolt, one for the module screw provided (hope it holds) and a third to fit over a stud on the coil to act as an anti-rotation feature. I did not want the thing to rotate into the flywheel. Also I fit the 45° side of the module up against the coil body to prevent its rotation too.

I believe I ended up with typical polarity +/+ and -/- in spite of what was suggested by AS. Perhaps I’m wrong. It’s really no big deal to test it out either way. Just leave enough room to reverse the spade connectors.

I put the ground wire under the coil bolt because it was thin enough not to cause poor thread engagement of my bolt. I then gooped the wires with hot glue to keep them from moving. (I hope it does not melt! Silicone would be better.)

The saw fired right up (after I remembered to tighten the flywheel! Duh!) I still have to tweak the mixture screws to get the idle under control. Runs fine WOT. That poor carb! I must have torn it down 6 times and it probably was fine all the time.

With Humility and Gratitude,

Captain Larry


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## MnSam (Mar 29, 2011)

Thanks much for the info, great job. Another 028 brought back to life .


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## Captainlarry (Mar 29, 2011)

View attachment 177917
View attachment 177918
Here are the NAPA instructions and receipt for 7-01749.


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## diskjockey (Nov 17, 2011)

i had the same probs with my old 028wb also i followed your posts and came down to the same problem would start and run barely did everything like you did and installed a new electronic mod from napa and shes running like a horse now no problems yet thanks for posting all the info for other people


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## Fish (Nov 17, 2011)

Also to add to the thread, a used electronic coil off of an 029 or many other newer saws can be used, just cut the wire to the points, hook up
the kill wire, and bolt it on and go.


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## Erndawg (Sep 25, 2012)

*thank you for this thread!*

Just recently picked up a 028wb on creigslist because I wanted a more professional saw for firewood. Been using a disposable 14"poulan which has been fine for me for a while but when it comes to the big stuff, doesnt cut it. Anyway. got a great deal on it and it ran great at first! Went to go cut some wood on the side of the road that the tree crews have been clearing the powerlines and it died on me half way through the first piece of wood. I first turned to the filter/gas line and they seemed fine, it was seeming to get plenty of gas! spraying back out the rear of the carb. I checked spark and had one so maybe throw another plug in.... 
I quickly turned to google and wondered if anyone else had this same problem with this saw.... This is where I found my answer. twenty bucks later for a chip and put it in without pulling the flywheel off,,the thing started with about a half of a pull on the rope. I love that saw, runs great!

Thank you so much all for posting these helpful tips. big help!


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## h4052 (Oct 9, 2012)

*What did we do before the internet*

I am new member and am I ever glad I found this website. 

Thank you _Erndawg _for your posting. I bought the electronic ignition on ebay (STIHL 028WB IGNITION) for twenty bucks. Worked just as everyone said. I have spent a couple of hours working on the carb. wish i would have started with the electronic ignition.

Thank you everyone for your postings...Eric


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## Captainlarry (Jan 14, 2013)

*Happy to Help*

Glad this post has seen some traffic and was able to provide some help. It was nice, too, to see greatful comments from members. Makes it worth the effort.

Saw On


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## Erndawg (Jan 16, 2013)

I just wanted to update my posting, In my case I had a bad coil in the end. I thought it was the chip and I put in the chip twice, my saw worked but only for about 10 min, each time. I was instructed that I just needed to switch to an electronic coil. So for 40 dollars, the saw runs mint now. Thanks again.
Erndawg:bang:


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## Fish (Jan 16, 2013)

Erndawg said:


> I just wanted to update my posting, In my case I had a bad coil in the end. I thought it was the chip and I put in the chip twice, my saw worked but only for about 10 min, each time. I was instructed that I just needed to switch to an electronic coil. So for 40 dollars, the saw runs mint now. Thanks again.
> Erndawg:bang:



So who else instructed you to just needed to switch?


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## BIG JAKE (Jan 16, 2013)

*just to add to the older saw owners knowledge base...*

I've had more than a few 028's and they are good saws. Just remember that alcohol in gasoline will ruin the fuel line over time especially if you leave fuel in it all the time. I picked up a seized 028 a while back for 25 bucks that had very light use over it's life. Found the fuel line in the tank looked like it had been stretched out to the point where it wouldn't hardly flow fuel any more. This is what alcohol does to them-turns them into sticky gum. Anyway, the cylinder cleaned up fine and with a new meteor piston/rings and a new fuel line I had an almost new saw. Replace the fuel lines every so often on any saw especially the older ones. 12 dollars is cheap insurance.


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## Fish (Jan 16, 2013)

Fish said:


> So who else instructed you to just needed to switch?



Wow, this turd sunk quickly to the bottom of the Punch Bowl, eh?


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## Erndawg (Jan 17, 2013)

I first bought the electronic chip from "lil Red Barn". The first one they gave me did the trick, I thought but worked for only ten min. So they thought they had a bad batch, they sent another, the second one did the same thing, So I called and told them what the issue was and they figured I needed a new coil. For an additional 20 bucks, they sent a new coil and now it has run perfect for months..


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## Wood Doctor (Jan 17, 2013)

*Here's to the Fish...*



Fish said:


> Also to add to the thread, a used electronic coil off of an 029 or many other newer saws can be used, just cut the wire to the points, hook up the kill wire, and bolt it on and go.


Fish, I was going to echo your analysis but OP solved it anyway. I ran into this same problem with an 046 and more recently with an older 084. All I did was pull the ignition module out and clean both it and the whole area around the flywheel. That rejuventated the spark and the engines in both machines both started purring like kittens once again. Both run today, the 046 after two years of hard work since the repair and both are using the original IM.

So much trash and goop can build up around the coil that one has to wonder how more of them don't short out or shut down more often than they do.


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## bagman69 (Jan 17, 2013)

*028*

Wow what a great thread and some great information, I have an 028 av super and id its great to know what to do and what to look for if my saw peters out. Thanks guys.


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## Wood Doctor (Jan 17, 2013)

bagman69 said:


> Wow what a great thread and some great information, I have an 028 av super and id its great to know what to do and what to look for if my saw peters out. Thanks guys.



Note that this thread applies to both the 028 and just about any saw that Stihl makes. Many repair shops would proabably have replaced the coil (IM) automatically and sold you a part costing $100 and added another $50 for labor. Then they would added a new spark plug, replaced the fuel filter, thrown in another $20 for good measure, and you would have walked away after dropping about $200 or so.


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## tomdcoker (Jan 17, 2013)

Captainlarry said:


> Ok, I ruled out some things, I think.
> 
> (1) I switched the gasket/main diaphragm order and (2) set the inlet control lever so it is flush with the diaphragm floor. It was pretty high, so I bent it down a tad. A high lever would mean a rich setting, right? So it should be more lean now. I think that I see less (none) raw fuel coming out of the muffler now too.
> 
> ...



On checking the fuel flow. I use a dollar turkey baster for that. Tom


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## Captainlarry (Feb 5, 2021)

I thought to get on here and look around regarding my Jotul Firelight and a Granberg Saw Mill. And and I saw I had a recent PM looking for the photos on this old post. It has been a long time since I've been on. Things have changed. I'm now dubbed a lurker and good'old Fish is on Account Hold. I don't know where the photos went. I'll try to post them again.

Saw Overview 


Original Points and Condenser



Ignition Removed



NAPA Part



Housing wire hole sealed.



Saw ready for new ignition.


Module Installed



Hope this helps.
Now on to my original searches!


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## HarleyT (Feb 6, 2021)

The loss of the pics of the old posts was a great loss, and many great members left here one way or another.


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## Mad Professor (Feb 9, 2021)

HarleyT said:


> The loss of the pics of the old posts was a great loss, and many great members left here one way or another.


I rebuilt an old build that lost the pictures as I still had them stored. Maybe others could too?

We lost lots in the site crash.


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## Captainlarry (Mar 30, 2021)

I was not aware of this. Well, I'm glad to be back. And while I won't visit often, I'd like to have my"lurker" status removed.


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## pioneerguy600 (Mar 31, 2021)

Captainlarry said:


> I was not aware of this. Well, I'm glad to be back. And while I won't visit often, I'd like to have my"lurker" status removed.


 Post a few more times and that status should change automatically.


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## HarleyT (Mar 31, 2021)

pioneerguy600 said:


> Post a few more times and that status should change automatically.


Can I get my "A-Hole" status removed?


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## Mad Professor (Mar 31, 2021)

HarleyT said:


> Can I get my "A-Hole" status removed?


Have you seen the Proctologist?


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## pioneerguy600 (Mar 31, 2021)

HarleyT said:


> Can I get my "A-Hole" status removed?


 I thought you were proud of that!


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## HarleyT (Mar 31, 2021)

pioneerguy600 said:


> I thought you were proud of that!


Actually, it would be nice to have really. 

I think that I have earned it!!!


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## HarleyT (Mar 31, 2021)

Or maybe "Instine"..


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## pioneerguy600 (Mar 31, 2021)

HarleyT said:


> Or maybe "Instine"..


Remember ,Bruce Hopf?


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## HarleyT (Mar 31, 2021)

pioneerguy600 said:


> Remember ,Bruce Hopf?


Who could forget????


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