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Post by Brennan on May 5, 2020 1:56:05 GMT -5
Well I've got 3 saws now that have these blasted carburetors and all three suffer from major spitback issues. Now if it was only one of my saws doing this id put it down to old saw issue but 3 is starting to show a pattern, and I think it has to do with the tool on the end of the screwdriver. I've always tuned these with 1 1/2 turns out on each screw, adjust low for best acceleration and high listening for the 4 stroke noise, but I've never been able to get the high rpm noise I was looking for without going into the less than 1 turn on high territory, which coming from walbro land is a scary proposition. However after reading some literature and other forum posts people are saying as much as half turn off of seat is the place to be (!), someone who maybe has a few more years experience can set the record straight here hopefully.
For reference the problem saws are: Homelite sxl-925 With a HS151b high side 1/2 (!) turn out when acquired, Skil 1616 type 1 with a HU18a high side 2 turns out when acquired, Stihl 045 superII with a hs211a high side 1 1/4 out when acquired.
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Post by Hoggwood on May 5, 2020 3:10:55 GMT -5
Well I've got 3 saws now that have these blasted carburetors and all three suffer from major spitback issues. Now if it was only one of my saws doing this id put it down to old saw issue but 3 is starting to show a pattern, and I think it has to do with the tool on the end of the screwdriver. I've always tuned these with 1 1/2 turns out on each screw, adjust low for best acceleration and high listening for the 4 stroke noise, but I've never been able to get the high rpm noise I was looking for without going into the less than 1 turn on high territory, which coming from walbro land is a scary proposition. However after reading some literature and other forum posts people are saying as much as half turn off of seat is the place to be (!), someone who maybe has a few more years experience can set the record straight here hopefully. For reference the problem saws are: Homelite sxl-925 With a HS151b high side 1/2 (!) turn out when acquired, Skil 1616 type 1 with a HU18a high side 2 turns out when acquired, Stihl 045 superII with a hs211a high side 1 1/4 out when acquired. With regard to the HS-151, it is a semi-fixed on the main nozzle. I have a variation on one of my 922's (HS-163/4?...got to check). They were designed to moderate fuel in an attempt (likely) to keep them from burning up. I have run into the same carb on 77cc Pioneers. I tend to block the high speed governors on most of mine as well (just a preference). That being said, I run mine on the happy rich side still at about 3/8 out. In the memo for that carb, it was suggested that one might even have the need to set or barely open that H. I can dig out the memo tomorrow. I would advise making certain your saw has good seals and is nice and tight if you go the route of blocking the governor and setting that needle low. That semi-fixed jet coupled with the high speed governor likely saved thousands of them from burning up and/or masking air leak symptoms somewhat.
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Post by sweepleader on May 5, 2020 8:41:34 GMT -5
Looks like Cory covered the SXL-925 pretty well.
Discussions of the other "s" brands should go to Off Topic or perhaps to the Arborist Site. There may be people here to help with those other saws but there are for sure at AS.
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Post by Brennan on May 5, 2020 10:21:44 GMT -5
The reason I posted here is that I’m looking for a theory of operation and tuning for these carbs, not specific saw advice. What do you mean by block the high speed governer, is this referring to the hole in the center of the brass bit on the metering side?
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Post by Jarhead ☠ on May 5, 2020 11:36:26 GMT -5
The buzz ball!, the brass screw on the side of the carb. Remove it and block the hole off with a small disc and replace the screw.
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Post by Brennan on May 5, 2020 12:03:44 GMT -5
Ah ok, I probably won’t remove it because I’m always scared of blowing an old chainsaw to bits but I will get in there and clean it out since the sxl carb was full of what is best described as molasses. It will also get a new gasket set as the metering diaphragm was quite crisp. Any idea on metering lever set position for the hs carbs?
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Post by Jarhead ☠ on May 5, 2020 12:09:19 GMT -5
The RK23HS kit is needed, I always do OEM and the lever should be flush with the carb floor.
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Post by edju1958 on May 5, 2020 14:16:53 GMT -5
Another thing you could do is what I did.I replaced the HS151A with an HS26A.You can also use an HS73,HS96,& I believe an HS67.All of these carbs were used on the earlier 900 series saws.Trust me,you won't blow your saw to smithereens.The HS151A was designed to be idiot proof so that wannabe mechanics who thought they knew how to tune a saw couldn't get the hi side too lean.If a saw is set too lean it won't blow up,it'll just seize.
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Post by Brennan on May 5, 2020 20:50:52 GMT -5
Well I pulled the carb on the “S” saw apart and low and behold someone set the lever flush with body (Walbro spec) instead of flush with the bottom of the chamber. Runs like a top now.
The sxl got the same treatment and the lever was a smidge high but more importantly the “buzz ball” was gummed up wide open (thanks for the info on that Dude). Also running like a top, except for a very well dulled chain. (Think cutting concrete with a saw chain) I know these saws won’t literally grenade but I run all my saws pretty heavy on the oil (between 32 and 40:1) and well in the safe range because as a broke teenager I can’t afford new pistons and cylinders if one goes.
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Post by sweepleader on May 6, 2020 8:01:16 GMT -5
The goo is due to use of ethanol fuel, avoid it or dry the say out every time you are done running it. I use only non-ethanol fuel in all my small engines. It costs very little in a year's time and prevents a huge amount of trouble. Even so, I try to dry stuff out when I am done with it.
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Post by Brennan on May 6, 2020 9:29:33 GMT -5
Yeah ethanol is really the devil in small carb like this. The sxl carb was the worst I’ve seen on a chainsaw but judging by the well rusted bar and chain this thing hadn’t run for a while. I use a good quality oil that has stabilizers in it and rarely does a tank of fuel sit for more than a month without getting used up and new fuel added so the extra hour drive for ethanol free stuff is hard to justify
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