Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Poulan => Topic started by: Drew_Uth on November 22, 2016, 02:37:29 pm
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So I have 5 micro series saws I have been rehabbing to gift and or sell, plus two to keep. Mostly 2.0 craftsman units, with two Daytons thrown in. I have a common issue with each one- carbs have been rebuilt with new gaskets, cleaned, new fuel lines, etc. While running them, when they idle for somewhere between 5-10 seconds, they load up and almost die. If you keep cutting and blipping the throttle constantly they run fantastic, but let it set idle for a few seconds and then whack the throttle again and they blubber, smoke and then clean out.
If I set the L any leaner, they have no throttle response and wont run right at all. In one unit, I put a longer metering lever spring in and that seemed to help a bit. I replaced the needles in each carb. Is my thought that the diaphragm pressure is exceeding the metering spring valid? Can you think of any other causes? I really don't think it is a mixture screw adjustment because they all run great otherwise. But it is baffleing that I have 4 runners and they all do the same thing!
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WAG Have you looked into the reeds under the carbs?
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If you blew them out with high pressure air you may have damaged the nozzle check valve. That will give you idling issues.
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I can't see this for all of them, but old clogged fuel filters? Idle may not pull enough gas through.
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Just a home owner that likes the older better made machines
Craftsman 3.7
Echo 290evl
Husqvarna 36
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New fuel filters
Have not looked super closely at the reeds...in my (dirtbike) experience, bad reeds prevent the engine from running at all, but maybe these are different because they have a fuel pump rather than relying on crankcase vacuum to draw fuel into the carb?
Regarding high pressure air, I did not. But the item you mention, where in the carb is it located/what purpose does it serve? I can jet a motocross or enduro bike to perfection but I am only about at about 60% understanding of how these tiny carbs work.
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I assume you have a WT carb on yours. The reed is located under the carb. You would have to remove the carb and the box it's mounted in to access the reed. Make sure it's flat and seated and that there is no crap or rust on the reed where it needs to seal against the plastic.
Here's some reading from Walbo.
WT manual
http://www.walbro.com/wp-content/uploads/2016/01/WTseries.pdf
General service manual. Good reading here on how they work and issues
https://app.box.com/s/vee4p32zuxpb2xnfvlm05wjaibsizekk
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You say if you set the L leaner. Where are you at on L from lightly seated?
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These saws have a LONG fuel line (something like 15") that snakes up and over inside the handle and then down to the carb. If the pump section of the carb isn't 100% and/or the impulse signal is weak............they'll run like you describe. You've rebuilt the carbs, so we can focus on the impulse signal. A leaking reed (grit under the reed, 'tired' reed that won't lay against the carb box surface, etc) can give a weak signal. Leaking crank seals will too.
Every Micro I've brought back into service has benefited from crank seal replacement. They're easy to get and cheap too. 530019059 from any Husky/Poulan parts source (including your local Husky dealer). Should be around $3-$4 each. Chicago Rawhide/SKF 4913 will also work, although they'll probably be more expensive than the OEM seals. Seals on these saws are SUPER easy and quick to change too. I harp on crank seals a lot..............but in my experience they're a "must replace" when rehabbing an old saw for work. They're rubber items with a finite life. They degrade over time just like fuel lines and carb diaphragms....
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Because both the H and L circuits of the carb feed from the same metering chamber, the barometric pressure of the metering chamber must be kept below atmospheric barometric pressure or the fuel stops flowing. The high speed nozzle which is fed by the H circuit, has a check valve contained somewhere in its system to prevent atmospheric barometric pressure from seeping past its check valve and back into the metering chamber. Some of these valves are screens that are wetted by fuel, and others are of a mechanical check valve style. The mechanical check valve style nozzle has been more problematic than the screen type. All of the screen type systems are serviceable, but the mechanical check valve types are not. The reason is some of the components are not sold by the carb manufacturer. I guess they want you to buy a new carb? Navigate over to Walbro's website and look up the carb. The parts listing will show which components are used. Before I bought any carbs or parts though I would go with what Eccentric posted and replace the seals and all of the fuel line.
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Thanks all for the excellent responses. I will order some crank seals and swap them out, it sounds like a good place to start and at that price its not like I am concerned about throwing "good seals" away. I will check the reed(s) as well.
They are all running Walbro carbs. Interesting detail- they aren't all identical. The first difference I noticed was that one or two had three screws for the diaphragm cover, while the other 2 had 4. Then I noticed one that had a much bigger venturi than the others. I have already given one saw to a BIL and lent one out, so I can't check those, but I have three carbs in my shop right now and two are of the smaller variety and one is larger. Naturally I put the larger one on the saw I plan on running the most ;D
Cut4Fun- I will have to get back to you on the L setting. I tune them to run the best, I rarely count turns; but I know that is the best way to have a discussion like this.
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So, I am having a lot of trouble getting the crank seals. I see them advertised for the $3-4 price, but they are all NLA. Two local Husky dealers in my area have basically told me GFY, they are of no help. Anyone have a source? At that price, I would by 6 seals. There are some on eBay at around $9 plus shipping...those are my last resort I guess.
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I'm in on a break from cutting deer. Post part # and I'll give a quick look before I go back out.
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530019059
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530019059
The main place that sells them OrderTree.com shows them NLA again too. So till they restock like that have in past if we get lucky. Going to have to find NOS or bite the bullet and pay the shipping.
(http://www.ereplacementparts.com/images/part_p_620858_3863108786.gif)
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@Drew_Uth How many you need? I found 5 at $6 apiece plus shipping will be $3 for all of them. Then shipping to you if we split the order.
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Well I wanted 6 but I will settle for 2 to get one up and running 100% and confirm that they fix the issue. Shipping to 08215 for me.
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Well I wanted 6 but I will settle for 2 to get one up and running 100% and confirm that they fix the issue. Shipping to 08215 for me.
I dont have them in hand. That is what I can get them for shipped to me. 5x $6 + $3 = $$33 for 5 to my door.
I can show you so you can buy them all and bypass me. ?
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Sure, if you can let me know your source that would be great. I will likely just order 4. Thanks!
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Sure, if you can let me know your source that would be great. I will likely just order 4. Thanks!
PM sent.
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Because both the H and L circuits of the carb feed from the same metering chamber, the barometric pressure of the metering chamber must be kept below atmospheric barometric pressure or the fuel stops flowing. The high speed nozzle which is fed by the H circuit, has a check valve contained somewhere in its system to prevent atmospheric barometric pressure from seeping past its check valve and back into the metering chamber. Some of these valves are screens that are wetted by fuel, and others are of a mechanical check valve style. The mechanical check valve style nozzle has been more problematic than the screen type. All of the screen type systems are serviceable, but the mechanical check valve types are not. The reason is some of the components are not sold by the carb manufacturer. I guess they want you to buy a new carb? Navigate over to Walbro's website and look up the carb. The parts listing will show which components are used. Before I bought any carbs or parts though I would go with what Eccentric posted and replace the seals and all of the fuel line.
Good info. The HDA164 carbs come to mind when talking about problematic mechanical check valves.
When I worked for Sears Service in the early 1990's, a Poulan rep came by the shop one day. One of the topics he covered while talking with us was the WA/WT Walbro carbs used on basically all of the Poulan manufactured 2-stroke machines that Sears sold. I remember him admonishing us to NOT blow out the carb bodies with high pressure compressed air, as the non serviceable mechanical check valves in those carbs can easily be damaged that way.
We also discussed the large number of WA/WT series carbs that we were having unsuccessful rebuilds with. The failure rate was high enough that we were replacing carbs on warranty work instead or kitting them (and were attempting to talk non-warranty customers into replacing the carbs rather than rebuilding). Our list cost for the carbs was about 2X the price of the kits. The book labor charge for replacing the carb was 1/2 the book cost for rebuilding the carbs. For the customers, it was basically a wash..............and we could bang out the job while they waited.
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So, I am having a lot of trouble getting the crank seals. I see them advertised for the $3-4 price, but they are all NLA. Two local Husky dealers in my area have basically told me GFY, they are of no help. Anyone have a source? At that price, I would by 6 seals. There are some on eBay at around $9 plus shipping...those are my last resort I guess.
They've gone NLA before. They've always came back in stock after a while however. Hopefully, that'll happen soon. The seals used on the 2700-3600/3450/2750/etc saws have also gone NLA a couple times, and have thankfully came back. Those seem to be more of an oddball than the seals used on the Micros, with no known easy industrial matchup, unlike these 530019059 seals that can be replaced with an SKF4913. You can get the SKF 4913 from bearing houses and auto parts outlets.
Homelite 94638 and 07025 are also seals that can be used. They were used in the E-Z/Super E-Z/XL-1/etc and XL/XL2/Super2/240/etc families. I have replaced the Homelite seals (in Homelite saws) with 530019059 seals in the past, as they were the easiest and cheapest to get. Lately I have seen a bunch of the Homelite seals on eBay, sometimes for reasonable prices. That's a change, as they were $$$ previously. That's why I went with the Poulan seals.
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So, I am having a lot of trouble getting the crank seals. I see them advertised for the $3-4 price, but they are all NLA. Two local Husky dealers in my area have basically told me GFY, they are of no help. Anyone have a source? At that price, I would by 6 seals. There are some on eBay at around $9 plus shipping...those are my last resort I guess.
They've gone NLA before. They've always came back in stock after a while however. Hopefully, that'll happen soon. The seals used on the 2700-3600/3450/2750/etc saws have also gone NLA a couple times, and have thankfully came back. Those seem to be more of an oddball than the seals used on the Micros, with no known easy industrial matchup, unlike these 530019059 seals that can be replaced with an SKF4913. You can get the SKF 4913 from bearing houses and auto parts outlets.
Homelite 94638 and 07025 are also seals that can be used. They were used in the E-Z/Super E-Z/XL-1/etc and XL/XL2/Super2/240/etc families. I have replaced the Homelite seals (in Homelite saws) with 530019059 seals in the past, as they were the easiest and cheapest to get. Lately I have seen a bunch of the Homelite seals on eBay, sometimes for reasonable prices. That's a change, as they were $$$ previously. That's why I went with the Poulan seals.
Thanks for the info. We had wonder about a replacement SKF
@Drew_Uth