Help with Old Stihl 028

[UOFan]

Hi all,

I picked up an 028 for $10 at a scrapyard back in April, and been messing with it off and on since…still can’t get it to run. Been taking up space on my workbench and I figured I might get some help here.

Bottom line, something is messed up with the air/fuel delivery. I have spark, compression, and I can get it to run with ether for about 2 seconds so I think the magneto is fine. If I can get it to run it basically red lines itself, max RPM.

I have a new Chineseium carb, replacing the (also looked new) chineseium carb it had on at the scrapyard. I haven’t messed with the idle screws on this new one yet.

I have a few questions with pictures:

First, I replaced this cracked line, looks like a fuel tank vent but it doesn’t lead anywhere. Is this correct looking? Also, not sure what the broken ground wire is supposed to be/do. I have good spark.

Next, when I have choke on, the butterfly is slightly open, more so than when choke is OFF. Seems it should be the other way around, cutting down air when choke is on. Is this supposed to be this way?

Choke off:

Finally, when I flip the saw to off, this black wire makes contact with a metal bar. Is this essentially shorting the spark to ground, shutting it off? Just wondering for my own knowledge:

Here’s how the saw has looked the past 8 months…I appreciate any help! It’s a pretty cool saw, made in West Germany.

 

[dieselscout80]

One thing to consider is possibly that the base gasket/seal between the cylinder and the case may be leaking.

 

[UOFan]

One thing to consider is possibly that the base gasket/seal between the cylinder and the case may be leaking.

Any way to do that without a dedicated leak down tester? I’ve got a compression tester and vacuum tester.

 

[dieselscout80]

Any way to do that without a dedicated leak down tester? I’ve got a compression tester and vacuum tester.

I’m not sure I’m not a knowledgeable 2 cycle guy.

 

[WinterDeere]

paging @xyz123

 

[RandyT]

Let me give some assistance in the pictures. The replaced line is the tank vent. Second the 028 carb doesn't have a choke. That is the throttle plate in the carb when in the start position is held partially open. The choke on the 028 is in the air filter. So when the on/off/choke lever is put in the choke position is moves the flap in the air filter to the choke position and also pushed the throttle linkage to partially hold the throttle open for starting.

And on a saw that old there could be a very good chance that either the cylinder to crankcase seal is leaking or the crankshaft seals themselves have failed.

 

[UOFan]

Let me give some assistance in the pictures. The replaced line is the tank vent. Second the 028 carb doesn't have a choke. That is the throttle plate in the carb when in the start position is held partially open. The choke on the 028 is in the air filter. So when the on/off/choke lever is put in the choke position is moves the flap in the air filter to the choke position and also pushed the throttle linkage to partially hold the throttle open for starting.

And on a saw that old there could be a very good chance that either the cylinder to crankcase seal is leaking or the crankshaft seals themselves have failed.

Thanks for the detailed response. Could a clogged tank vent cause issue with starting? I can’t seem to suck fuel through the line when I try.

I’ll recheck compression today and post the numbers. I seem to remember I had good compression back in April when I bought it. Not really sure how to test the seals, could I just plug all the holes, push 10 PSI of compressed air into the spark plug hole, spray with soapy water and check for bubbles?

 

[xyz123]

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

 

[dodge man]

I have a friend with a similar saw and yes the choke is in the filter setup. Take a look and you’ll see how it works. It’s not that tough to break it down further and replace the seals. I’d also be curious what the piston and rings look like on the exhaust port side.

 

[RandyT]

Not really sure how to test the seals, could I just plug all the holes, push 10 PSI of compressed air into the spark plug hole, spray with soapy water and check for bubbles?

7 psi is the standard for pressurizing the crankcase to leak check the seals. Too much pressure can push out the crankshaft seals.

 

[WinterDeere]

It’s not that tough to break it down further and replace the seals.

I'm often blamed for scope creep, the "might as well, while I'm in here," problem. But the reality is that an ounce of prevention is always worth a pound of cure, and if he already has it torn down this far...

There are few things I hate more than finally getting something back together, and then finding a new problem I could've prevented, if I'd gone just one step further before backing out.

 

[Snobdds]

The choke set up in the filter is problematic. After years of use, the plastic deforms and it gets hard to make a good seal of the choke to get proper function.

Also, never start a saw with starting fluid or either. There is no oil in starting fluid and it will score your piston.

A tank vent breaks vacuum only. It doesn't vent anything. When fuel is used, air needs to replace the fuel to keep the vacuum going for fuel delivery.

I would stay away from chinese carbs. You will chase your tail with those things. It's far better to get an OEM carb and put a new kit in it.

 

[Eagle1]

The choke set up in the filter is problematic. After years of use, the plastic deforms and it gets hard to make a good seal of the choke to get proper function.

Also, never start a saw with starting fluid or either. There is no oil in starting fluid and it will score your piston.

A tank vent breaks vacuum only. It doesn't vent anything. When fuel is used, air needs to replace the fuel to keep the vacuum going for fuel delivery.

I would stay away from chinese carbs. You will chase your tail with those things. It's far better to get an OEM carb and put a new kit in it.

Which OEM carb is NOT made in China today? Example there are any number of Walbro carbs of the same part number by various factories with minor (or major) differences fit, finish and quality. For the MS361 I know of Famertec, old Stihl and new Stihl as well as a number of no name (or private label).
I get the idea of OEM parts but for the price you seldom get a better product since they come from the same place the as the NO name after market. YMMV
Your choice is the Stihl carb made in China by the Zama or the Zama carburator made in China or the no name carb made in the same factory in China. It not a global supply chain.

Walbro carburetors are made in several global locations, with primary manufacturing in China, Japan, Mexico, and Thailand, alongside facilities in the United States, serving diverse engine markets, with some high-precision units often coming from Japan and high-volume production in China and Mexico

Zama carburetors are made in multiple locations, primarily in China (Huizhou) and the Philippines (Santo Tomas, Batangas), with significant R&D and headquarters in Japan (Iwate) and Hong Kong, and a US sales/engineering office in Tennessee. Zama is the world's largest manufacturer of diaphragm carburetors for outdoor power equipment

Stihl carburetors are primarily made by their subsidiary Zama in China (Huizhou) and the Philippines (Santo Tomas), with some older or specific models also originating from Japan, and occasionally even Ireland, though they are components within Stihl's global production network for quality assurance. While Stihl has German roots and US facilities, carburetors are a specialized part, often sourced from these dedicated Zama plants for cost-effectiveness and quality control, ensuring they meet Stihl's high standards.

 

[Snobdds]

Which OEM carb is NOT made in China today? Example there are any number of Walbro carbs of the same part number by various factories with minor (or major) differences fit, finish and quality. For the MS361 I know of Famertec, old Stihl and new Stihl as well as a number of no name (or private label).
I get the idea of OEM parts but for the price you seldom get a better product since they come from the same place the as the NO name after market. YMMV
Your choice is the Stihl carb made in China by the Zama or the Zama carburator made in China or the no name carb made in the same factory in China. It not a global supply chain.

Walbro carburetors are made in several global locations, with primary manufacturing in China, Japan, Mexico, and Thailand, alongside facilities in the United States, serving diverse engine markets, with some high-precision units often coming from Japan and high-volume production in China and Mexico

Zama carburetors are made in multiple locations, primarily in China (Huizhou) and the Philippines (Santo Tomas, Batangas), with significant R&D and headquarters in Japan (Iwate) and Hong Kong, and a US sales/engineering office in Tennessee. Zama is the world's largest manufacturer of diaphragm carburetors for outdoor power equipment

Stihl carburetors are primarily made by their subsidiary Zama in China (Huizhou) and the Philippines (Santo Tomas), with some older or specific models also originating from Japan, and occasionally even Ireland, though they are components within Stihl's global production network for quality assurance. While Stihl has German roots and US facilities, carburetors are a specialized part, often sourced from these dedicated Zama plants for cost-effectiveness and quality control, ensuring they meet Stihl's high standards.

AI responses should be banned.

The carb that came on that saw originally was not made in china.

I have no idea what point you're trying to make here...

 

[Eagle1]

AI responses should be banned.

The carb that came on that saw originally was not made in china.

I have no idea what point you're trying to make here...

Point is that trying to find a replacement that is NOT made in SE asia is difficult unless you have parts saw. I do not believe anyone is making old model parts in Germany these days.

 

[Snobdds]

Point is that trying to find a replacement that is NOT made in SE asia is difficult unless you have parts saw. I do not believe anyone is making old model parts in Germany these days.

Two seconds in Google. Spending $40 more than the china price will save tons of time and frustration. Plus it will run better.

GENUINE TILLOTSON CARBURETOR FOR STIHL 028 028AV HU-40d 1118 120 0600 | eBay

FOR STIHL 028 028AV. GENUINE TILLOTSON CARBURETOR. TILLOTSON PART NUMBER: HU-40D.

www.ebay.com

 

[WinterDeere]

I'm not sure where Stihl makes the OEM carbs that come on their BG-56 blowers, but I've had more than one, and they all fail in the same way after a few years. They work great for a few years, then begin to flood and hydrolock the engine, sometime around year 3.

Oddly enough, the Chinese replacements I buy for like $9 on Amazon don't exhibit that failure, but keeping them tuned after year 2 is a bit like chasing your tail.

Which is worse? I'm not sure, but the only total engine siezures I've ever experienced with those BG-56's were on OEM carbs, not the Chinese aftermarket ones. One was resolved by simply pulling the plug and pumping dry, the other was unrecoverable.

Like Eagle, I had assumed that even the OEM carb was cheap junk made in China.

 

[zzvyb6]

My Super has a primer bulb that got a tiny split in it from the flexible material getting stiff (like my knees). Look for air bubbles in the return line.

 

[UOFan]

Thanks guys for all the responses. I appreciate all the insight. Compression is between 135-140, so fine from my understanding.

I do understand that the choke is in the air filter element, but I figured the throttle plate (what I called the butterfly) wasn’t supposed to move…which I now know that’s fine. Checking that off the list.

Regarding the carb discussion, when I say Chinesium, I’m just meaning the no-name stuff off Amazon >$15. I will shell out money for Mikuni on my ATVs, but honestly I get away just fine with Amazon garbage on all my smaller stuff I’ve had to replace. I know they can be hit and miss, but I can’t justify $40 carb for a $10 45+ year old saw when I already have a fully functioning MS271. I will try to stick with this chineseium carb for now.

Thank you for whoever mentioned that about starting fluid potentially causing cylinder wall scoring. Would putting some 2 stroke oil down the spark plug port be acceptable to mitigate this, or should I just refrain from using ether on 2 strokes?

Finally, any secrets to getting this thing to run, even rough? Assuming it’s fuel related (I haven’t ruled that out yet) and I need to minimize ether use. It’s got a high and low speed screw, haven’t touched them yet.

 

[UOFan]

A tank vent breaks vacuum only. It doesn't vent anything. When fuel is used, air needs to replace the fuel to keep the vacuum going for fuel delivery.

So in this case, should I be able to suck fuel from the tank vent (with a full tank of full? Or blow some compressed air into the vent line, and have it exit the fuel tank?