Help with Old Stihl 028

[UOFan]

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.

I screw crap up all the time by over repairing, it causes headaches but I like learning. I’m in the middle of un-f***ing an ATV and pull behind spreader…both things I decided to rip apart because “they probably needed some grease or something”.

None of the stuff I work on is related to my income so no worries if equipment is down for a couple weeks while I figure it out, and I’ve got enough backups of key items (transportation, really) that it’s fine.

The saw for me is just another fun project, trying to get experience on all things mechanical so I can better teach my kids how to fix things when they get older. So I enjoy all the wisdom on this forum.

 

[dodge man]

On the screws there is probably a starting point for them. I don’t know how many turns to get them close but hopefully someone will chime in. They could be closed all the way. I don’t know how a carb is delivered.

 

[WinterDeere]

I don’t know how a carb is delivered.

Most seem to be delivered at or near the nominal starting point... unless someone prior has opened the box and turned them.

If you can't find specifics for your saw, try around 1 turn out on Hi and 1 to 1.5 turns out on Lo. Most are close enough to this setting to get it running, and then start tuning from there.

 

[RandyT]

Most carbs as previously said come close enough for initial start. And look at the saw next to the carb screw adjustment holes in the side of the saw. Most stihl will have a counterclockwise circle with a number printed next to it. Made be 3/4 or 1 or 1-1/4

 

[stevem5215]

About the carb quality, I've had more than one Chinese made carb that didn't function at all. And wouldn't start the equipment it was installed on. I usually had to do as already recommended to you which is to get a carb kit from someone else and rebuild and reclean the original carb. The only exception has been when the original carb is so far beyond repair and in that case the equipment I'm fixing is usually the same and is junked. Scored cylinders is a problem. They do sell Starting fluid with oil in the can to assist in starting 2 strokes. Look for it when buying that stuff. It'll say it on the can. It's the only starting fluid I buy.

 

[xyz123]

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.

 

[D'oh]

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.

 

[denchen]

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.

 

[ScipioUSA]

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.

 

[Pinecrest]

I have a Guy at ACE Hardware, all he does is maintain Stilh engines
for all the Lawn Service Companies ....he can look at one and tell you what is wrong and what it will co$t to Fix/ and when you get it back it Runs better than it ever did !

 

[dodge man]

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.

 

[4Liberty]

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.

 

[xyz123]

I have a Guy at ACE Hardware, all he does is maintain Stilh engines
for all the Lawn Service Companies ....he can look at one and tell you what is wrong and what it will co$t to Fix/ and when you get it back it Runs better than it ever did !

Your lucky and rare these days. Here ace stihl had a locals saw for almost a year.

Couldnt figure it out throwing parts at it and racking him up a big bill on a saw not worth 50-75 IMHO. Putting new carb, new flywheel, new coil etc etc.

I told him get your saw and let me check it. He did. I could tell what it was in seconds. Low psi and pulled muffler scored. Duh on them and shame on them.

Stihl even has a checklist they are suppose to follow.

 

[Tbone07]

1. Almost no point in troubleshooting anything else until you get a proper leak-down test done. Genuine Stihl or Chinesium carb, doesn't matter if you have a leak.
2. There are leak down tester kits out there for sale, or you can build your own through McMaster Carr like I did. Takes awhile to get proper fittings, but it's worth it. I use a bulb like you see on a blood pressure cuff. You cannot just blast air in there, could blow out the seals.
3. Chinesium carb definitely isn't preferable, but you should at least get it to run enough for you to know it's capable. Then again, it's a crap shoot with those cheap carbs
4. Compressions testers can be inaccurate, but they rarely read high. Yours probably ok, look through exhaust port check for scoring and general condition
5. $20 says the last owner threw an Amazon carb on and fooled with it awhile, then gave up because it was old and who cares?
6. Don't throw it away if you give up on it. Someone will take it for parts if nothing else. Like me

 

[4Liberty]

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

Still using the compression release?

 

[Snobdds]

1. Almost no point in troubleshooting anything else until you get a proper leak-down test done. Genuine Stihl or Chinesium carb, doesn't matter if you have a leak.
2. There are leak down tester kits out there for sale, or you can build your own through McMaster Carr like I did. Takes awhile to get proper fittings, but it's worth it. I use a bulb like you see on a blood pressure cuff. You cannot just blast air in there, could blow out the seals.
3. Chinesium carb definitely isn't preferable, but you should at least get it to run enough for you to know it's capable. Then again, it's a crap shoot with those cheap carbs
4. Compressions testers can be inaccurate, but they rarely read high. Yours probably ok, look through exhaust port check for scoring and general condition
5. $20 says the last owner threw an Amazon carb on and fooled with it awhile, then gave up because it was old and who cares?
6. Don't throw it away if you give up on it. Someone will take it for parts if nothing else. Like me

I think you mean a pressure/vacuum test. Two stroke motors need zero air leaks anywhere. If you don't have a pressure vacuum tester, use a can a brake cleaner. While the engine is runing, spray around the flywheel and clutch, if the motor dies...you have an air leak. If those pass, spray around the intake behind the carb, same thing, if it dies, then you have an air leak.

However, investing in a pressure/vacuum tester saves a lot of time and frustration. You can test fuel lines, impulse lines, and carbs with the tool.

Your #6 is very important...I would rather have a good used part than a new chinesium part.

 

[dodge man]

Still using the compression release?

That saw doesn’t have a compression release.

 

[danielk]

Still using the compression release?

My saw, a different stihl, has a compression release. Is there a problem with using these?

 

[WinterDeere]

My saw, a different stihl, has a compression release. Is there a problem with using these?

I have decomp valves on some of my saws, and it always seems to me that a saw that's been sitting on the shelf any period of time takes many more pulls of the cord to start, if the decomp valve is depressed. It's hard to set up a double-blind test on this, as I'm sure the number of pulls of the cord is going to vary on any saw that's been sitting awhile, even if you kept all controllable variables the same. But it seems to me I usually achieve a cold start in 3 pulls or less without decomp, versus a half dozen or more with decomp pressed.

I suspect this is because the decomp valve might reduce the amount of vacuum pulling fresh fuel up thru the carburetor, and so it might not affect fuel-injected saws nearly as badly.

Because none of my saws that have decomp valves are that difficult to pull start, I usually just don't bother pushing the decomp button.

 

[bgr]

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.