Help with Old Stihl 028

[4Liberty]

Have read most of the posts and notice no one has mentioned the carb to cylinder boot. If memory is any good I know some Stihls used a metal ring in the carb end of the boot
If you don't have recommend you purchase a hand held vacuum/pressure pump, plug the exhaust and intake port and take a vacuum pressure test of the cylinder/crankcase. Take a compression test and should at bare minimum 100psi although more is better.
As for trouble shooting it sounds as if you have proved ignition, but have a fuel supply issue or a leak. The pressure/vaccum test would prove that. If a fuel issuel be sure the tank, filter, and supply line are clean and the fuel line free from cracks and breaks. And one last point be sure the pulse line is in good shape and is aligned at the carburetor.

I did several posts back.

 

[Bentrim]

I did several posts back.

Sorry somtimes just to lazy to read and remember what I have read.

 

[skysentinel]

I would definitely reattach the black ground wire. If this is an anti-vibration model, then the wire is to insure that the engine mount section is grounded to the handle frame. (My part labeling nomenclature may not be accurate, but I hope you'll know what I'm talking about)

Also, you won't be able to pull fuel through the tank vent hose. It is not designed for that.

I'm wondering if the engine would respond to a squirt of starter fluid into the carburetor? Also, when you try to start the engine, you'll need to make sure the carb air intake filter assembly is mounted properly, as the choke is mounted on it.

 

[Michael In Tennessee]

I have this exact saw. I also, right now, have the same problem. Won't run. I'll be working on it later today.

I have read this thread, probably don't remember all of it, so I might repeat stuff.

First, just some info specific to this saw.

No OEM parts available, so you are stuck with aftermarket.
The little yellow line, as already mentioned, is a vent. Its fine. Can't suck fuel through it, shouldn't blow into it.
The fuel pickup is a pre-molded line. If necessary, you can buy a replacement.
The pulse line is a pre-molded line. Ditto.
The intake boot is a pre-molded line. Ditto.

The saw has a 4 position run switch. Off, Run, high idle, and choke. The reason the butterfly is partly open when choked is that the saw is intended to start cold at high idle. The start procedure is to choke the saw when cold. Crank until it just fires. Move the switch to high idle and continue pulling to start. It should only take one or two pulls. Then, when you pull the throttle, it releases the high idle notch and the switch moves to run all by itself. When hot, just starting from run is usually sufficient.

First principles: You need spark, fuel, ignition, compression (and timing).
Timing is almost surely right, you can verify it if you tear down by checking the flywheel key.
You already checked compression. Even if the cylinder is scored, it should start.
You are not quite sure on fuel and spark.
Verify spark. Carb installed, air filter removed. Squirt some pre-mix into the carb. This will act like its choked. Does it fire and run for a few seconds? If so, spark is good. If not consider replacing the coil with a more modern one that doesn't require points. The points and condenser are obsolete, so don't even try to fix them. You can leave them in place or delete them. Doesn't matter. This coil fits... Amazon.com

A fuel issue could be bad fuel/air issue caused by a leaking/torn intake. Intake boots can be damaged by continuous use with bad rubber isolators. You can actually tear the boot in half. I've done it. In my case, it was because I threw the saw down to avoid a running saw meeting my face while I tripped. Don't do that. Inspect the intake boot. Hard to see, but worth a look.

If you have good spark, work on fuel. Either you have a carb issue or a fuel pickup issue. Fuel pickup issue can be two things. Either the fuel line is damaged/filter clogged or you are not getting sufficient pulse to run the carb pump. Inspect the fuel line. Remove it and look it over. If you remove it, you can blow in one end and plug the other to look for leaks.

If all good, inspect the pulse line. Make sure it is attached to the block. Make sure the carb plugs into it correctly. Look for cracks. Real hard to inspect further without disassembling a bunch of stuff.

Now we are down to case leaks (which is what I suspect I have a problem with). Can't really inspect the crank seals without tearing the saw half apart. remove the clutch assembly, remove flywheel. In my case, I didn't feel like testing, so I just replaced the crank seals. Saw started running fine. But now it doesn't. I suspect one or the other of the seals walked out of position. Only have a few hours on the saw since the seals were replaced. But, it could just be the 3rd party replacement seals were just junk. Don't know just yet.

I have not done a seal test because I didn't want to fabricate the needed carb and exhaust blank off plates. I guess I might need to do that. If so, I'll 3d print some plates. I'll cross that bridge when I need to.

This is the seal kit I used. Only used the shaft seals. As cheap or about the same price as just the two seals. Amazon.com

Also, as mentioned, check the exhaust screen for blockage. I really doubt it, but you never know.

Regarding the missing ground. Won't affect the saw starting. However, it will affect the saw stopping. Might have to pull the plug wire if you get it started. Be aware and safe.

 

[Dale M]

One thing that you can check is the exhaust screen. A lot of times it will get plugged up and will cause the engine to choke off.

 

[RobertN]

Married With Small Engines does good diagnosis on 028

 

[Merck]

I've owned them and they have a cult like following. But I compared my 028 super I had to a 026 and 026 was for me over 028. So always just sold them off.

Without a proper vac pressure testing. If you can keep it running long enough you can take starter fluid spray and spray around seals, base gaskets etc. If you hit a spot where air leak it will shut off saw immediately.

Another for just seals is turn on side while running then turn to other side. If really bad seal it will shut off one way or another or just drop really bad idle or raise up.

Your china carb can be hit and miss too. 50/50 shot it is works on them sometimes.

All just WAG's over the net without having saw on bench. GL

View attachment 4692642

That is a fantastic saw if you can get it running. They haven't sold it in the US for probably 40 years maybe more. It was banned by the EPA or something like that. It was and may still be sold over seas.
That being said, I don't know how available parts will be. I owned one and wish I had it back. The selling point and stuff is straight from a Stihl dealer when I went to replace mine that in my ignorance I sold to a guy. I am not real good on small engines. Just trying to let you know what you have.

 

[MDchanic]

I have no real information here.
Just wanted to say I've got an 028 that I picked up somewhere, not running, I rebuilt the carb and installed new fuel lines (which, if I recall, were a bi__h to fish through the requisite holes), had it start and run well, used it for an hour or two, and then the darned thing wouldn't do more than sputter and try to run.

It made me angry, so I tossed it in a corner.
That was about four or five years ago.
I recently stumbled upon it, sitting in a puddle of bar oil, cleaned it, and put it in its case.

This thread has given me a bunch of ideas and things to check, so I may just dig it out and mess with it again. I really liked it when it worked, and I'd like to use it again.

Thanks for the advice and motivation!

– Eric

 

[xyz123]

That is a fantastic saw if you can get it running. They haven't sold it in the US for probably 40 years maybe more. It was banned by the EPA or something like that. It was and may still be sold over seas.
That being said, I don't know how available parts will be. I owned one and wish I had it back. The selling point and stuff is straight from a Stihl dealer when I went to replace mine that in my ignorance I sold to a guy. I am not real good on small engines. Just trying to let you know what you have.

I fixed and sold that 028 super long ago. I compared to my 026. 026 more to my liking. So off it went.

The 026 went later. Friend liked it.

Husky 353 346 was even better then them, so no issues selling 026's either. Just a tool and replaceable.

 

[aircommuter]

Crankcase leaks that don’t show with dirt and oil residue is common on these two cycle engines. There are types of two cycle engines that don’t incorporate the crankcase like these type do. While they are two cycle they have valves in the head and cam operated injectors. In order to solve a problem you have to understand the problem.

 

[UOFan]

Thank you to everyone for the last two pages of replies, tonight I am going to read them all and responsd.

I spent the last week heavily focused on getting this quad up and running, to good success.

I am going to get back on the chainsaw this week. Here’s the Yamaha 350 all fixed up:

 

[UOFan]

Just to add some context, when I got the saw from the scrapyard it had a brand new (cheap) carb on it, along with a brand-new (cheap) fuel line and air filter + air filter housing. The previous owner obviously was having issues as well.

This week i'll run through everything short of pressure testing - if that does nothing i'll get a pressure test kit and check those seals.

Another thing, i've been pull-starting it without the bar attached and the plastics off. This week i'll put the plastics back on during testing to limit the airflow through the filter a bit.

Would having the bar/chain attached have any impact? My intuition is no, but just asking to be certain.

From my old racing days. I just use oil squirt cans with mix. I used to have one with alky and one gas mix.
But now both just gas mix for shooting a bit in carb with throttle pulled. Sometimes through a plug hole.

View attachment 4708555

Thanks for this, i'll do this on all my 2-strokes instead of using standard starting fluid from now on.

That Green Coloured fuel line is suspect, check in the Tank, see if the line is Squishy/Gummy, while in there, replace the Foam Fuel Filter.

That's brand new el-cheapo line I put on, the old one was essentially destroyed. I just took the foam fuel filter off to eliminate another variable. Ill probably buy some name-brand fuel lines as another poster recommended.

I would check, then double check the fuel pick up pipe. The slightest of crack or pin prick hole, and you would draw in air instead of fuel. Make sure the pipe is compatible with your fuel. Many new fuels have stuff that makes lots of pipe go brittle. I had a chainsaw a couple of months ago, that everyone and their dog have had a go at, turned out it was a pin hole where the pipe passed through into the fuel tank entrance rubber olive. Even after I had found it, it was a job to see.

Good thought, i'll do that. Haven't thought of a pin-hole leak in that line. It was essentially brand-new (the line) when I got it at the scrapyard. I have another one from a carb kit.

How does the piston look if you pull the muffler off? I would pressure/vac test the saw before you go crazy. That way you can figure out if you have a massive air leak that you are trying to work around.

Also, do you know if it still has points? A common upgrade was to clip the points wire and use the "Universal" coil instead. One less thing to fiddle with.

I haven't checked - going to do this tonight. It does still have points, at least from what I remember when I took it mostly apart in May.

One reason myself and someone else said take a look at the piston is you can get bad scoring. This was a MS250 I rebuilt. I’m still not sure what happened to it, probably straight gas but maybe an air leak. It’s not a great picture but it’s looking in the exhaust port and you can see how the piston and rings are scored in the lower left of the picture.
View attachment 4721416

I appreciate the picture, i'm going to do this tonight.

Sounds like it’s leaking air somewhere. How’s the rubber hose that the carb mounts to? Are the clamps tight? If it’s leaking there it will do exactly what you described, as well as the cylinder base gasket or seals. A loose clamp or the rubber boot are much easier to fix. At any rate none of it is really difficult. If you get around to doing seals be extra careful with the flywheel nut. They must be exact torque and it’s inch pounds. Too loose sheared keys too tight and you’ll twist off the end of the crank. Ask me how I know . They are really easy to work on don’t be scared. If you do the base gasket I haven’t put one back in yet. I used gasket eliminator you gain compression.

It does seem like an air leak somewhere, what is this rubber boot you're talking about? Between the carb and the head there is a single (thin) gasket, no rubber boot. I'll try to take a photo tonight.

Been a while since I have worked on my saw, but isn't there a crankcase vacuum hose to the carb to supply the pressure pulses to operate the fuel pump on the bottom of the carb. I remember not getting fuel because I had not found a bad hose.
I also remember a lot of new chinese carbs which did not work and now look for OEM carbs.
The emission control carbs on the new saws don't rebuild well, but the old carbs rebuild OK with a good kit.

I will check this tonight.

"If I can get it to run it basically red lines itself, max RPM." this sounds like an air leak from the base gasket or crank seals. If you have checked eveything else you could take it to a saw shop and have them do a pressure test on the crankcase.
That is still a very popular saw, check out youtube videos on teardown and repair of this saw. I rebuilt one recently that I got from a neighbor. Pretty much all the rebuild parts are available aftermarket . Once you understand how to work on them its pretty easy to completely go through one and have a great running saw.

After I exhaust all other options this week, i'll probably go get a pressure test kit. I am relatively determined to fix this saw.

Have read most of the posts and notice no one has mentioned the carb to cylinder boot. If memory is any good I know some Stihls used a metal ring in the carb end of the boot
If you don't have recommend you purchase a hand held vacuum/pressure pump, plug the exhaust and intake port and take a vacuum pressure test of the cylinder/crankcase. Take a compression test and should at bare minimum 100psi although more is better.
As for trouble shooting it sounds as if you have proved ignition, but have a fuel supply issue or a leak. The pressure/vaccum test would prove that. If a fuel issuel be sure the tank, filter, and supply line are clean and the fuel line free from cracks and breaks. And one last point be sure the pulse line is in good shape and is aligned at the carburetor.

Where is this boot? I only have a gasket between the carb and the head, that's how I got it at the scrapyard....would be interesting if it was simply missing a component. Compression is good, between 135-140 psi. Ill check out that pulse line.

 

[UOFan]

Alright, I found AN issue tonight. While checking the carb to cylinder boot (I found it) I noticed the vacuum/return line that the carb fits into was severed. I’ll post a picture below. Someone mentioned this in a post too. From what I’ve read here (trying to remeber) this line creates vacuum that helps the carb pick up fuel.

Also, cylinder was scored vertically, just a bit. Picture is having trouble uploading but I could see three or four vertical lines.

Looks like I have to take most of the saw apart to replace this broken line:

 

[ScipioUSA]

Alright, I found AN issue tonight. While checking the carb to cylinder boot (I found it) I noticed the vacuum/return line that the carb fits into was severed. I’ll post a picture below. Someone mentioned this in a post too. From what I’ve read here (trying to remeber) this line creates vacuum that helps the carb pick up fuel.

Also, cylinder was scored vertically, just a bit. Picture is having trouble uploading but I could see three or four vertical lines.

Looks like I have to take most of the saw apart to replace this broken line:

View attachment 4779705

That's your impulse or "pulse" line. That's both an air leak and a problem for moving fuel into the saw.

You can replace it a lot easier with a set of forceps. You can also pull the mounts and see about separating the handle from the main body to give yourself room to work. Don't be surprised if you have a bad mount or two, the bar oil gets them shot pretty quickly.

You mentioned you still have points. I would strongly suggest getting the Stihl "Universal" coil and slipping you point wires instead of fooling with them. Gap the replacement coil to the flywheel with a business card and call it good.

Depending on the level of scoring you have, it may or may not be an issue. I ran a few of my saws for years with some carbon scoring before it became an issue.

But glad you found the main problem to start!

 

[RobertN]

Alright, I found AN issue tonight. While checking the carb to cylinder boot (I found it) I noticed the vacuum/return line that the carb fits into was severed. I’ll post a picture below. Someone mentioned this in a post too. From what I’ve read here (trying to remeber) this line creates vacuum that helps the carb pick up fuel.

Also, cylinder was scored vertically, just a bit. Picture is having trouble uploading but I could see three or four vertical lines.

Looks like I have to take most of the saw apart to replace this broken line:

Check out those Married with Small Engine videos . Erica gets in to the nitty gritty on that.

That Impulse line leaking before it broke could have caused lean condition that cause the scoring you're seeing.

 

[dodge man]

The cylinder is scored or the piston? I posted the picture earlier of the badly scored piston and rings. I ran the saw for a while with that damage. When cutting it ran fine but it wouldn’t idle. When I took it apart the cylinder was scored badly also. That saw had a lining in the cylinder called nikasol(sp?), like a hard chrome. I ended up getting a new piston, rings, jug(cylinder) and a few other parts for about $100. Taking the saw apart and putting it back together doesn’t take all that many hours but cleaning all the old saw dust and oil off everything takes time.

A picture of the bad piston and most of the parts cleaned up.

 

[WinterDeere]

Taking the saw apart and putting it back together doesn’t take all that many hours but cleaning all the old saw dust and oil off everything takes time.

A big compressor with a fat air hose and nozzle at 100 psi can make quick work of the cleaning job, if you don't mind wearing all of the blowback on your face and clothes. This is how I clean my saws a few times per year, and especially at end of each season. Wear good safety glasses, or goggles!

 

[dodge man]

A big compressor with a fat air hose and nozzle at 100 psi can make quick work of the cleaning job, if you don't mind wearing all of the blowback on your face and clothes. This is how I clean my saws a few times per year, and especially at end of each season. Wear good safety glasses, or goggles!

I do that also. When you start taking one apart you realize how much sawdust and oil accumulate in places that don’t blow off. The saw dust mixes with the bar oil and just stick in crevices.

 

[UOFan]

Thank you guys for the replies - I will be getting the impulse line tomorrow and starting work tomorrow evening. I will be watching those videos to get a feel for it, YouTube is such a good resource.

I may upgrade the points ignition in the future, but I just need to get it cutting first.

Dodgeman I mis-typed, it is the piston that is scored, thank you for the correction.

I have a big old 1960s SB air compressor that I use often…I always were eyepro because yes, blasting off the oil/sawdust mixture caked on the saw seems to just always find its way into your face.

 

[WinterDeere]

I do that also. When you start taking one apart you realize how much sawdust and oil accumulate in places that don’t blow off. The saw dust mixes with the bar oil and just stick in crevices.

All too true, especially with standard air gun nozzles, which are nearly always have a little 1/8" NPT tip.

But I have one air nozzle with a 3/8" diameter ID bore straight thru the tip, and no side vents. Likely not OSHA-approved, but when run that on 1/2" line with 3/8" fittings, it'll damn near blow the paint off the saw. The little thing has recoil!

I find that particular nozzle can literally suck oily sawdust out of blind crevaces, by creating a vortex of low pressure (venturi effect) around the area at which that nozzle is directed. I'm sure you'll still find areas to wipe down, in a full disassembly, but not much!