Help... Stihl 028 AV Super

[Dale]

"There are two nipples on the carburetor. The fuel line hooks to one. The other nipple faces straight towards the cylinder, parallel to the carb mount bolts. As you slide the carb onto the bolts, this nipple engages the impulse hose."


Ahhhhhhhhhhhh !!! I was calling that an exhaust port. So, remove the handle and replace the hose and rubber boot if it shows wear... GOT IT. This hose ends up in the cankcase ? I'm assuming there is no filter on the other end of the impulse hose right ? Thanks.

 

[TonyM]

The other end of the impulse hose hooks on a nipple at the cylinder. There is no filter. It opens directly to the crankcase. Also, I've had two saws with the same intake boot design as the 028 that would not seal at the carburetor to intake boot junction. I used a little (very thin coating) of permatex on the carb to fix the problem.

 

[lostone]

Dale check your PM and get back with me.

 

[Al Smith]

Pictures

They say a picture is worth a thousand words.In one of the pictures ,my old greasy finger is pointing to the impulse line.As luck would have,I just disassembled the 038 yesterday,for repairs[ broken piston,ugh],thus the photo op.The other picture shows the fuel shut off lever,on a Tillotson,model HS carb,Walbro and Zama,are similar.Sorry about the fuzziness of the pictures .If anybody wants to fix them,have at it.

 

[lostone]

Well looks like Al has it covered, I had a photo for him also but looks like you beat me to it Al.

 

[Al Smith]

Go ahead and send it.The more,the merrier.Could show things in a diifferent perspective.

 

[Dale]

Purr'n now !!!

I changed the impulse line and the saw is running like a true champ, but I'm not so sure there was a problem with the old one. I didn't realize how much you had to remove in order to replace the line, and there has to be a trick that makes it easier to line up that rubber baffle to the exhaust port, SHEESH. I finally got it to seal well after about a 30 minute fight. The old line wasn't cracked, but I'll tell you what I found. When diconnecting the black coil wire, to break apart the saw, I found that the wire was bare for approximately 1/2". I'm wondering if it didn't cause a short that would knock the saw out. Well it was either the impulse, or the bare coil wire as I still had the problem after mixing a new batch of gas, a carb. tune-up, and new fuel line and filter. Hey I look at it as routine upkeep right ?

Hey Al, that line that you are pointing to in the pic looks nothing like the impulse line that I changed. The one I changed was thicker and ribbed black rubber.

Thanks for all the help fellas, looks like I'm ready for a new sprocket since the old one is showing wear, so that's next. I'm surprised to see Stihl reccommends changing the sprocket after every 2 chain replacements.

 

[lostone]

I believe Al's was a picture of an 038, is that right Al? that he was working on but it would give someone an idea of what and where it was to change it.

 

[Lakeside53]

There is a quick trick to feeding the the rubber carb boot (I think this is what you meant when you say "exhaust port"?) through the carb mount in the tank assy. Connect it to the cylinder first, wrap a couple of turns of string around the carb end of the boot, thread through the tank hole and pull gently... It will just pop nicely into place.

 

[Dale]

Good Tip

Lakeside,
Good tip. I utilized that method with fishing line while pulling the fuel line that I replaced up from the tank to attach to the carb., being careful of course not to cut into it.

I'll tell you what I was concerned with while doing the exhaust to carbureutor boot. The boot ever so slightly comes in contact with the carb mounting rods and creates 2 small impressions where they make contact. I had to keep twisting on the boot to line those "impressions" back up because I was fearful of an airleak if I didn't get them back to where they originally were.

 

[Lakeside53]

Lakeside,
Good tip. I utilized that method with fishing line while pulling the fuel line that I replaced up from the tank to attach to the carb., being careful of course not to cut into it.

I'll tell you what I was concerned with while doing the exhaust to carbureutor boot. The boot ever so slightly comes in contact with the carb mounting rods and creates 2 small impressions where they make contact. I had to keep twisting on the boot to line those "impressions" back up because I was fearful of an airleak if I didn't get them back to where they originally were.

The trick to geting the carb boot on correctly is to line it up on the cylinder first. Don't twist the boot more then very slightly after it's clamped to the cylinder. I can't remember the 028 specifically (and it's too ???? cold out in the workshop to look right now!), but most Stihl Cylinders have a mark or tab cast onto the exact bottom of the intake, and the boot has a similar mark or tab. Line these up and the mount screws will fit nicely into the "dents".

I use a soft non-fluffy twine. Fishing line probably isn't the best.

 

[Al Smith]

Yes,that was an 038 Mag,in the picture.It might not have been the original impulse line,and as I recall,most of the Stihls I've worked on had that segmented type hose.I work on several over the year that have had some very interesting repairs done to them,before they come my way. A set of long medical forceps,work real good for changing those pesky impulse lines.They sell pretty cheap,on e-bay.It'a bit of a challage to get my fat fingers,into some of those spaces.Glad you got the saw running.

 

[Dale]

Thanks Al,
The saw is running, but I haven't tried it under load yet, so I have my doubts whether the carb. is tuned yet.

Do you have any tips on tuning the carb. on an 028 ? I was told start at 1 turn out on the H/L screws and go from there.

 

[mjw]

lets get back to the basics.get yourself a can of carb cleaner.NOT A CAN OF STARTING FLUID!!!!!!!!!!!!!!!!i cant tell you how many saws and small 4 atv motors because of starting fluid.starting fluid will remove the oil off your cylinder.just try it on a peice of metal with oil on starting fluid will clean it right up.well enough about starting fluid lets get to the problem.take the carb cleaner squirt some in your carb and try to start it if it starts your problem would be a fuel problem.carb or fuel lines.if it will not start it is probally an ignition problem.take your spark plug out and check for spark NOTE [BEFORE YOU CHECK FOR SPARK MAKE SURE THAT THERE IS NO MORE FUEL OUT OF THE SPARK PLUG HOLE]

 

[Wayne Busch]

Just found the site and have been browsing around, you all seem to be extremely knowledgable and rabid chainsaw fanatics. Boy can I use some help with my 028 Super.

A little background. I'm a weekend warrior, and probably only cut 2-3 cords per year, but I am very careful and courteous when it comes to TLC for my saw. I bought the saw used for $170 in 1991 and boy do I LOVE IT. Well my pullcord broke, so I buy a new one, and notice the tension spring (for the pullcord) is a bit rusted and worn so I replace it also. Now mind you, up until this point the saw has been running like a top (for 14 years now). Well I yank on the new cord and after a bit longer than normal, it starts, runs for 10 seconds or so, and dies out. I choke it, throw it on start and it does the same thing, runs a bit then dies out. OK, I figure it's been a while since I cleaned the carb, so I get a kit and redo it (gaskets, needle, spring), I also replaced the fuel hose as it had some wear cracks, and fuel filter. Fille er up with gas and SAME THING. Now I was told to close noth the H and L screws on the carb, and then back them off 1 full turn. I did that, and it won't start at all now. I've seen mention of some kind of ignition coil, could this be a problem ? Oh, I also replaced the spark plug. I may try to mix a new batch of fuel since it may be "bad" for some reason, but I really doubt that is it. Well do you fellas have any suggestions ????? I am really frustrated, and I just love this saw to death.... it's always been one heck of a dependable worker for me. Thank you.

The early model 028 came with points and condenser. Later models some where around 1985 came with electronic ignition. Two things I would look at. Take to a GOOD stihl dealer and have the crankcase vaccum and preasure tested. It should hold .4bar either way. This will check for any leakage from seals, gaskets etc. The have the ignition system checked with a JST 5000 meter. This will show the reserve voltage your coil will produce. If it is low <15k volts (point type) or <17-20K volts (electronic) and higher than have the reading under compression, then the coil is bad.

If I had to make a guess and assuming that carb, fuel and compression is acceptable AND the saw is point ignition. I would say a new ignition module part # 0000 400 1300 is in order.

I would strongly advise going to electronic if this is the fault. Part is about $100.00 though.

Wayne

 

[Fish]

If you get around to it, remove the carb again, take it apart agian, remove the needle
and try to look through the hole, with the other side of the carb disassembled. It is
possibly obstructed.

 

[stihltech]

module

Those aftermarket modules will replace the points nicely on an 028, iit is the first saw I remember putting them on. But, I don't ever remember seeing a super model with points.