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McCulloch Chain Saws

Discussion in 'Chainsaw Stickies' started by Bruce Hopf, Jun 28, 2008.

  1. rwoods

    rwoods Addicted to ArboristSite

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  2. edju1958

    edju1958 ArboristSite Guru

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    Jason,the key word in the service bulletin is MOST carbs,it didn't say ALL carbs.I'd say to take the carb off,it's gotta come off anyway,& pull the extra diaphragm out that wasn't in it originally,put it back together & see if it makes a difference.I'll bet any money that that's the problem.Like I said,I rebuilt an SDC carb for a 10-10 back in Dec.& I didn't put two diaphragms in & my 10-10 purrs like a kitten.
    Ed
     
  3. Jasonrkba

    Jasonrkba Addicted to ArboristSite

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    Thanks Ed. I'll get on it in the morning. I need to get this one out of the way, that homelite is spread across my whole bench in a million pieces. I have a string trimmer, hedge trimmer and two more saws on deck.:eek:
     
  4. edju1958

    edju1958 ArboristSite Guru

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    I hear ya Jason,I have about 6 saws tore down right now too.BTW,I saw your post over on HOH.If you need parts let me know,I'll hook you up with Bob Johnson,he's my go-to guy for parts.
    Ed
     
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  5. Jasonrkba

    Jasonrkba Addicted to ArboristSite

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    ED I appreciate it and may hit you up.
     
  6. Aaron Rybicki

    Aaron Rybicki ArboristSite Operative

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    Hate to be beating this somewhat dead horse, but I'm carrying this over from the Unofficial Mac 10-10 thread...

    I've had issues with 2 different Mac 10-10 saws with Walbro SDC Carbs. Both saws ran fine and were tuned properly, but when they were turned clutch side down they would start to bog as if they were being starved of fuel. Both had new fuel lines, filters and carb kits (and no fuel leaks from anywhere). Crank Seals for the PTO side and Flywheel side were replaced on both. They were both recently rebuilt and both had their crankcases sealed with Permatex Motoseal. Spark is strong and blue for both. Could not figure out what was causing this issue. I had a couple of Mac 10-10 Parts saws laying around that I knew ran good positioned at any angle. So, I took the carbs off of them and threw them on the saws with problems and now they run fine (no bog/change in RPM) at any angle!

    Now, I just bought a very decent SP81E off of eBay (for a great deal actually..) and it had the same problem... Would bog with the PTO side facing the ground. However, this saw in particular had a Tillotson carb. I replaced it with a NOS Zama carb and now it has fixed the bog problem....

    The only variable that changed in all of this was the Carburetor. It has to be something in the hardware of the carburetor... What it is, I do not know.
    Does anyone have an idea what would cause this??? Would be nice to get some use out of the problem SDC carbs if I could fix them somehow..
     
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  7. Brian Thacker

    Brian Thacker ArboristSite Guru

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    Aaron, richen up the low just a little and it will quit that.

    Brian
     
  8. Aaron Rybicki

    Aaron Rybicki ArboristSite Operative

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    I'll try it when I get a chance to tomorrow and throw a problem carb back on.. It's just odd.. I could've sworn I've tuned all (4) carbs, the problem (2) and the properly working (2) very much the same.
     
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  9. Aaron Rybicki

    Aaron Rybicki ArboristSite Operative

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    Here's the SP81E :rock:. I let a friend run it for the video. Was on eBay advertised as 160lb of compression. Maybe some of you seen it. When I got it, it tested at 183lb of compression. Not sure if it has something to do with the elevation, if my tester is reading high or their's was reading low.

     
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  10. vinnywv

    vinnywv Tinkerer

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    Those sp81,s are very good saws. Strong runners. Not heavy at all. My two are within 1.5lbs of my stihl ms290. Thats with 20" bars and chain plus magnesium vs plastic. Much more fun to operate also. You did do well on the price to. Congrats!
     
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  11. 2broke2ride

    2broke2ride Addicted to ArboristSite

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    I have seen that happen when the low screw is tuned too rich too. Fuel begins to puddle up in the crankcase at idle, then when you roll the saw it sloshes around and effectively floods it out.
     
  12. rocketnorton

    rocketnorton Addicted to ArboristSite

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    elevation & temp affects comp readings.
    need to be fairly big diffs, tho,
     
  13. 2broke2ride

    2broke2ride Addicted to ArboristSite

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    I'm working on my 1-86. I got it running good but I relieved I forgot to clean and service the oiler when I had the rest of the saw apart. It isnt working. I was able to get the two plugs, the check valve, and the spring out. But I'm having no luck getting the oiler piston out. Anyone have any ideas besides removing the whole gearbox again?
     
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  14. sawfun

    sawfun Addicted to ArboristSite

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    I had that kind of trouble with the manual oiler on my 895 and took the plug in the front out with checkballs & spring. Then sprayed some penetrant oil in and let it soak a few minutes. I pushed on it with a punch and the using the oiler button, back and forth until mine came out. It was just very gummed up from sitting for years.
     
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  15. edju1958

    edju1958 ArboristSite Guru

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    Spray some PB Blaster in there & let it sit for a day or two.That should loosen up any gummy stuff that's in there.I've already just sprayed it in the oiler & started pushing on the oiler button & it freed up immediately.Maybe I just got lucky,I don't know,but that stuff is awesome.
    Ed
     
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  16. heimannm

    heimannm Addicted to ArboristSite

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    Jason - one of those diaphragms is the real thing, probably rubber that lays on the machined surface of the carburetor and the other is likely Mylar and backs up the rubber diaphragm. You may have noticed the back up is cut out in the area of the oscillating portion of the diaphragm. Leaking fuel can be traced to a problem on the metering side, either the lever is set incorrectly or there is a speck of debris in the needle/seat area.

    I try to always remember and pressure test a carburetor before assembling it into a saw to make sure there are no issues.

    Mark
     
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  17. heimannm

    heimannm Addicted to ArboristSite

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    Kevin - You should find a plug on the front of the gear box, if you remove it you can push the manual oiler piston out or perhaps get by with some compressed air to pop it loose. If you use air, make sure you have a rag or something ready to receive it when it comes out so you don't have to call in search party.

    20180831_094526.jpg

    Mark
     
  18. Jasonrkba

    Jasonrkba Addicted to ArboristSite

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    I got it running today. The needle was not set right. I did pull the check valve diaphragm also. But.... I tore the fuel hose using needle nose to put it back on the carburetor. I will order another and hopefully thats a wrap. It does cough a little fuel while idling though.
     
  19. edju1958

    edju1958 ArboristSite Guru

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    Jason,just for future reference,I put the fuel line on by hand before I bolt the carb back into the air box.Yeah,it's a pain in the butt working with the linkages too,but much easier with the fuel line.I pulled a SDC carb off a 10-10 today to rebuild & it did have the extra diaphragm in it.The rule of thumb I use is:if it has the extra diaphragm in it when you pull it apart,then put the extra diaphragm back in when you're rebuilding it,if it doesn't have the extra diaphragm in it when you pull it apart,then leave the extra diaphragm out when you're rebuilding it.Simple,it works for me,especially when I know the saw was running previously
    Ed
     
  20. 2broke2ride

    2broke2ride Addicted to ArboristSite

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    Thanks guys, I will try all the tricks mentioned.
     

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