Noob advice for 028 AV S rebuild

[ashbugwoody]

Ok, making some progress here. Work finally is leaving me alone so I can concentrate. Got the Jug back on and just did the drive side seal. Made the orange seal sleeve using a piece from a long nose funnel. The seal starts real easy on the taper and transitions to the crank smooth. Got to do the other side and test and, fingers crossed, I'm on the home stretch. Assuming all goes well, I plan to break this in doing firewood and then shop my running 028. It has 40 year old seals and the compression is starting to go down.

 

[ashbugwoody]

Got it back together but having some problems with fuel. Rebuilt the Walbro carb and it doesn't seem to be getting fuel. Is there a way to prime after rebuild?

 

[SteveSr]

Got it back together but having some problems with fuel. Rebuilt the Walbro carb and it doesn't seem to be getting fuel. Is there a way to prime after rebuild?

What did you do to the carb during the rebuild? Do you have the diaphragms and gaskets on in the correct order? These older carbs are pretty simple. Did you use compressed air on the carb?

No fuel could be caused by lack of impulse caused by a crankcase air leak. Did you pressure/vacuum test the crankcase after you put it back together?

 

[ashbugwoody]

What did you do to the carb during the rebuild? Do you have the diaphragms and gaskets on in the correct order? These older carbs are pretty simple. Did you use compressed air on the carb?

No fuel could be caused by lack of impulse caused by a crankcase air leak. Did you pressure/vacuum test the crankcase after you put it back together?

Yes, pressure checked the case after reassembly. Only leaks were in my test hose fittings. New impulse line also. Cleaned carb out with carb cleaner. Definitely got the diaphragms and gaskets in right. Pulled my arm off, dry plug every time.

 

[SteveSr]

Yes, pressure checked the case after reassembly. Only leaks were in my test hose fittings. New impulse line also. Cleaned carb out with carb cleaner. Definitely got the diaphragms and gaskets in right. Pulled my arm off, dry plug every time.

Was the carb rebuild kit Walbro OEM? I have seen AM kits with dodgy / incorrect diaphragms.

Pressure test the fuel inlet to the carb starting at the fuel pickup. It should hold 7-10 psi indefinitely.

Does your carb have a black (or worse white) plastic fuel elbow? I have seen these crack and leak. If it rotates at all it is cracked. These are replaceable assuming that you can find the part.

Also check to make sure that the choke flap is closing all the way.

 

[ashbugwoody]

Was the carb rebuild kit Walbro OEM? I have seen AM kits with dodgy / incorrect diaphragms.

Pressure test the fuel inlet to the carb starting at the fuel pickup. It should hold 7-10 psi indefinitely.

Does your carb have a black (or worse white) plastic fuel elbow? I have seen these crack and leak. If it rotates at all it is cracked. These are replaceable assuming that you can find the part.

Also check to make sure that the choke flap is closing all the way.

Thanks for the info. It was an AM kit. It had parts for many different carbs. I think I used the correct pieces. Also, I didn't screw with the spring, needle and pivot. It does have the black plastic elbow. I'll do the pressure test, probably submerge in a glass of gas and blow / look for bubbles. The choke flap looks good. Previous owner (before rebuild) said saw was running Ok and quit while cutting a limb. When I disassembled it, the impulse line was cracked halfway through. Also noted that the mixture screws were turned in way lean of the 1 1/2 initial settings. After rebuild, compression is strong and new seals everywhere don't leak. I'm betting I made a stupid mistake reassembling carb or that elbow is cracked. Do you know if a Walbro wt 16a is interchangeable with a wt 16b? just curious, I have the 16a.

 

[Mad Professor]

I just posted a thread on a replacement metal fuel inlet for Walbros

Metal fuel inlet



I'm having an issue with my 028S too. Rebuilt carb (WT-16B) with OEM kit. Needle assy was fine, didn't replace that. Did gaskets/diaphragms. Main problem was the screen was plugged up which I replaced. Ran like a champ for a while, but a little hard to start. But now seems to have an air leak. I suspect the plastic inlet elbow which came loose (crack?) while working on carb. I suspect leak made carb hard to prime, then bigger leak is leaning it.

I always buy the full OEM carb kits. Sometimes you need all the parts. In my case I needed the screen filter. They only cost $2-3 more, and you'll still have the extra parts if needed.

When you work on a carb, lay out all the parts in the order they came off. Some kits will have parts for similar carbs too. Match up the new parts with old.

OP, were sure screen was clean when you rebuilt carb? I had to pry mine out and replace it.

 

[ashbugwoody]

I just posted a thread on a replacement metal fuel inlet for Walbros

Metal fuel inlet

View attachment 871118

I'm having an issue with my 028S too. Rebuilt carb (WT-16B) with OEM kit. Needle assy was fine, didn't replace that. Did gaskets/diaphragms. Main problem was the screen was plugged up which I replaced. Ran like a champ for a while, but a little hard to start. But now seems to have an air leak. I suspect the plastic inlet elbow which came loose (crack?) while working on carb. I suspect leak made carb hard to prime, then bigger leak is leaning it.

I always buy the full OEM carb kits. Sometimes you need all the parts. In my case I needed the screen filter. They only cost $2-3 more, and you'll still have the extra parts if needed.

When you work on a carb, lay out all the parts in the order they came off. Some kits will have parts for similar carbs too. Match up the new parts with old.

Thanks, I'll let you know what happens when I submerge that thing and put pressure on. Good to know the elbow is replaceable.

 

[SteveSr]

Thanks for the info. It was an AM kit. It had parts for many different carbs. I think I used the correct pieces. Also, I didn't screw with the spring, needle and pivot. It does have the black plastic elbow. I'll do the pressure test, probably submerge in a glass of gas and blow / look for bubbles. The choke flap looks good. Previous owner (before rebuild) said saw was running Ok and quit while cutting a limb. When I disassembled it, the impulse line was cracked halfway through. Also noted that the mixture screws were turned in way lean of the 1 1/2 initial settings. After rebuild, compression is strong and new seals everywhere don't leak. I'm betting I made a stupid mistake reassembling carb or that elbow is cracked. Do you know if a Walbro wt 16a is interchangeable with a wt 16b? just curious, I have the 16a.

I have seen bad AM kits. You also need to compare (overlay) the pieces that came out with the ones going back in to make sure that they match up. If still no joy get an OEM kit.

As I recall the Walbro letter designations only refer to minor changes that shouldn't affect function.

 

[ashbugwoody]

Have officially got a runner. The fuel problem was a bad fuel line. The shop that supplied much of the OH materials sent a replacement fuel line that was too long. I still don't like it because it hits the throttle linkage. When asked about it, they told me "its the line we use on all of our rebuilds". Yeah, well its not correct and its too long. Since I have a hard head, I tried to reuse the hose I had without checking it. Stupid move. Replaced that line and ran it for a few seconds with the bar off. Way too rich and a little boggy but wants to run. Returned the mix screws to 1 1/4 (H and L). Previously they were set to 3/4 - H and 1 - L. no wonder it burned lean.
Tomorrow I'll put the bar and chain on and check oiler. I didn't screw with that, so it will probably work.

Any break in advice, don't want to screw it up now. Also, thanks for the unbelievable help. Maybe there will be a junk 038 on my table next.

 

[CausticUC]

You dont buy your fuel line in bulk?

 

[SteveSr]

Have officially got a runner. The fuel problem was a bad fuel line. The shop that supplied much of the OH materials sent a replacement fuel line that was too long. I still don't like it because it hits the throttle linkage. When asked about it, they told me "its the line we use on all of our rebuilds". Yeah, well its not correct and its too long. Since I have a hard head, I tried to reuse the hose I had without checking it. Stupid move. Replaced that line and ran it for a few seconds with the bar off. Way too rich and a little boggy but wants to run. Returned the mix screws to 1 1/4 (H and L). Previously they were set to 3/4 - H and 1 - L. no wonder it burned lean.
Tomorrow I'll put the bar and chain on and check oiler. I didn't screw with that, so it will probably work.

Any break in advice, don't want to screw it up now. Also, thanks for the unbelievable help. Maybe there will be a junk 038 on my table next.

If that is an AM fuel line watch out! They tend to kink where it bends at the carb and will likely turn to mush in short order. This can cost you another P&C when it runs lean again.

You may be able to update the fuel hose to the new curved variety but you would need access to enlarge the hole in the tank from 8mm to 10mm. Someone else here might be able to tell you which one to use.

 

[Mad Professor]

You dont buy your fuel line in bulk?

It's a molded line, built not to kink, with a built in grommet to fit the hole in the fuel tank. It has to snake from right side under the carb/linkage to left side of carb.

Would be hard to make generic line work well.

 

[ashbugwoody]

You dont buy your fuel line in bulk?

No, this is my first go around. I have learned some of the mistakes I want to avoid in the future thought.

 

[ashbugwoody]

If that is an AM fuel line watch out! They tend to kink where it bends at the carb and will likely turn to mush in short order. This can cost you another P&C when it runs lean again.

You may be able to update the fuel hose to the new curved variety but you would need access to enlarge the hole in the tank from 8mm to 10mm. Someone else here might be able to tell you which one to use.

Of course it is AM. And of course, the shop selling it shows the correct hose then sends the long "Z" shaped hose. I'm trying to source the correct hose now. Luckily, I got the impulse line elsewhere and it is real OEM. The AM impulse lines are a joke.

 

[ashbugwoody]

It's a molded line, built not to kink, with a built in grommet to fit the hole in the fuel tank. It has to snake from right side under the carb/linkage to left side of carb.

Would be hard to make generic line work well.

View attachment 871215

Yep, that is the correct short hose. If you can tell me where to get a few I am looking. I'm only running the AM junk as a band aid.

 

[ashbugwoody]

Here is the AM hose supplied by the shop. Not the same dimension as OEM and not near the same material or quality. None the less, shop claims, we use it all the time. Don't make it right.

 

[Mad Professor]

Of course it is AM. And of course, the shop selling it shows the correct hose then sends the long "Z" shaped hose. I'm trying to source the correct hose now. Luckily, I got the impulse line elsewhere and it is real OEM. The AM impulse lines are a joke.

Get OEM, ~ $9. I've also had good luck with Stens (on a 038) if you go AM, not sure that they have it for 028?

 

[SteveSr]

Yep, that is the correct short hose. If you can tell me where to get a few I am looking. I'm only running the AM junk as a band aid.

That OEM hose is not optimum as it generally doesn't hit the bottom of the tank or reach the sides when the saw is turned on either side. Stihl upgraded it to the "S" shape quite a while ago. That is why I am thinking that one of the newer OEM "S" shaped hoses may be a better upgrade. You need to find one with a tank that is about as tall as the one on the 028. I am thinking that the OEM 026/MS260 is probably too short. Might try the 029/MS290 or the 036/MS360. Is there clearance on your 028 tank to get a 15/32" drill bit in to enlarge the hole in the tank AND not get in the way of the carb or linkage?

 

[SteveSr]

Here is the AM hose supplied by the shop. Not the same dimension as OEM and not near the same material or quality. None the less, shop claims, we use it all the time. Don't make it right.View attachment 871216

It works long enough for the customer to go away...