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Mac 250 difference?

Discussion in 'Chainsaw' started by mogulmasher, Jul 2, 2018.

  1. mogulmasher

    mogulmasher ArboristSite Lurker

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    In tank fuel filter looks good, I've already had tank apart to clean it out and reseal the tank gasket.

    Yes a small amount of raw fuel while idling in airbox area.

    Stud is tight....it actually came off with af cover when I first got saw so I e already addressed this issue.

    Carb is a hl63d.

    I'm reluctant to fiddle with adjustments too much just yet cause it did run good before. Not saying it doesn't need fine tuning, I bet it does, just don't think it's so far off that it's causing this problem. It's gotta be something stupid.
     
  2. mogulmasher

    mogulmasher ArboristSite Lurker

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    Can someone just give me a ballpark number of turns out on low speed screw so I can be sure it's not way off?

    I'm really into vintage sleds as well so pretty familiar with messing with Tilly and walbro pumpers....
     
  3. mogulmasher

    mogulmasher ArboristSite Lurker

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    Low speed was just short of 1.5 turns out from lightly seated.
     
  4. Okie

    Okie ArboristSite Guru

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    The front jet is the low speed. I've seen them be anywhere from 1/2 turn to 1 3/4.
    Back it out another 1/2 turn and test. Keep a mental note of the L & H jets setting for when it was running good It will be a good start for later if you have to go through the carb, etc.
    The little stud on top of carb that came off with the cover is suppose to have a little thin copper seal washer on it.
    I'm going to have to unplug my computer until tomorrow due to popcorn storms.

    The small amount of raw fuel in the air box is a bad thing and could be related to your issue.
    That carb has a internal fuel pump and if you are seeing raw fuel and it idles that kinda means the pump will suck air.
    Usually the OEM Mac fuel line on the bottom of the carb has a wimpy little pressure clamp and lets the fuel line leak, especially if the fuel line is rock hard. I replace that clamp with a itty bitty screwdriver type.
    If the leak is not at the fuel line that Tillotson #3 on my post on pg 2 may be correct.

    In meantime before I get back to you you can find a Tillotson carb kit for the HL-63D on flea bay and some real good HL carb info at the Tillotson site, shows IPL, adjustments, etc.

    If it has the old hard fuel line, plan on replacing it. I use tygon tubing for the fuel line.

    Be careful around the two bolts holding the carb. You will eventually find that your can just loosen them up and twist the carb sideways to remove and install. (but first time just take them completely loose and pay attention to the lip on the intake adapter, it's what causes the ears to break if not aligned.
    Also pay attention to the little hole in the manifold and GASKETS, its the fuel pump pulse hole.

    The kit for that carb HL-63D is a RK-88HL about $10 from flea bay and here is a link to your carb IPL
    https://tillotson.ie/wp-content/uploads/2015/07/techinfo_hl_us.pdf

    and you might see some additional Tillotson info at this link.
    https://tillotson.ie/resources/#manuals

    Heads UP notice; When you take out the single screw in the bottom cover on the carb, first place a witness mark on all the carb bodies, then peck and try to gently get the cover off without breaking the cork gasket and the sintered iron filter may stay in the cover. Do not break the filter screen, none is in the kit. Reason I say this is the kits new cork gasket usually is wrong size and the filter is usually hard to remove from the cover and can be cleaned in place with low pressure air backwards. injecting some ATF fluid into the gas input and let it soak for few hours will sometimes aid in getting the bottom cover off easier and saving the gasket. Do not try to clean the carb with direct injection of air or you WILL BLOW out a welch plug UN NOTICED and they are not in the kit. Just use low pressure 15# and do not direct inject the holes with air. Pay attention to the IPL gasket and diaphragm layout and don't get them upside down and backwards and the kit has different diaphragms and gaskets so match them up with your old ones as a guide.

    I soak those carbs in 50/50 mix of white vinegar and warm water for couple hours with good results.
    That carb is obselete, but A GOOD one will show up on ebay every once in awhile that needs a kit (for around $20 but don't buy one with scarred up screws) and you can use a HL-63A or HL-63E. ( these are interchangeable and a direct bolt in replacement. for yours) Other places they seem to be around $40-60 and need a kit.

    chainsawyers.com is a good place to review Mac chainsaw parts also.;)
     
  5. mogulmasher

    mogulmasher ArboristSite Lurker

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    Okie thanks for all the great info and tips! Just dug into it a bit and found a couple things. The fuel hose at carb was cracked. This was the leak into air box. I replaced fuel line. Also pulled carb and flipped it to tighten all screws, they took a tiny bit of a turn. Also, no copper washer under AF stud/bolt, so I put just a little bit of motoseal around it to seal it.

    Saw will run and rev a bit more now, but still cut out like starving for fuel. The in tank line is pretty soft, I bet it sucking shut under throttle. If that don't solve it will do a carb kit.
     
  6. Okie

    Okie ArboristSite Guru

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    Did you back the front low speed jet out CW little bit more and test for good rev?
    A cut out at wide open throttle can be good thing. Read below.
    You need to watch the air box. If you see any signs of gas, it's not right. (and the gas line on the bottom of the carb is a source of a small leak if you leave the old Mac clamp.

    Briefly carb adjustments: While the saw is warmed up and idling, take a small screwdriver and put a witness mark on the handle so as you can keep count of 1/4 turn, adjust the front carb screw in slowly starting at approx 1 1/2 turns out at start and listen to the idle of the saw and if engine speeds up and becomes smoother any further in and the engine may all at once die and really hard to start afterwards, so try to keep from going too far CW. When it gets to smooth idle the engine will usually stall (smother) when piss reved. Back the low jet out until the idle slows while trying to rev the engine. It should reach a place where it will take throttle. Then with the H jet at about 1/2 to 1 turn as the saw is reving to full throttle keep backing out on the H jet (making it richer) until you hear a 4 cycle gurgle pop at wide open throttle. This is called 4 cycling and lets you know the saw is running full throttle on the edge of rich unloaded.
    Then with a sharp chain take the saw to a log so as the chain will get a good bite and when the engine loads down little bit in the cut the 4 cycle will go away or the engine become smooth and as you lift the saw out of the cut it will cut out or 4 cycle. (turning the jet screws out enrichens the engine with fuel and keeps the piston cooler.
    Running the saw in a heavy cut with the H jet in CW to far can ruin a chainsaw piston quite fast due to running too lean and overheating the piston, so keep a heads up. A slight 4 cycle gurgle is a good thing.

    That little stud on top of the carb is a Mac test point for the carb fuel pump. Mac had a adapter that you could take that stud out and installed the adapter, connect a low pressure gauge (0-10lbs or so) to check the fuel pump pressure either while the saw was running or within 8-10 cranks the pressure should get to 1/2 lbs or so.
    I made a adapter using a bolt that I threaded (not sure, think is was like a 5/16-24 stud)same threads as the existing and stud and drilled little hole length wise and connected a gauge to check the fuel pump pressure on one of my troublesome saws while in a cut. (I found the carb sintered iron filter screen was clogging and would re-clog until I got the fuel tank clean of some really fine mold looking gunk that would get past the in tank filter)

    Maybe one of the guys on this site will post up a link of video of how a chainsaw saw should sound 4 cycling
    in and out of a cut and adjusting the carb for the 4 cycle sound. If I have it on file I'll post it later.

    My opinion is if the air box is now staying dry you need to get familiar with how the carb is adjusting before doing a kit. It might be ok.
    Keep a heads up on the carb to intake adapter gaskets, some get rock hard and need replaced. I just make them myself and keep a heads up and keep the two gaskets properly aligned when re-mounting the carb and the adapter. Hard gaskets here can lead to trying to overtighten the carb (which is not necessary and breaking off a manifold ear.
     
  7. mogulmasher

    mogulmasher ArboristSite Lurker

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    Didn't mess with adjustments since it was late and it's loud. Might have time tonight. Thanks for all the tuning advice!

    You said you use tygon for fuel line. I have some but it's OD isn't big enough to seal to airbox so I just used some 1/4" rubber fuel line I have. Do you use a grommet with the tygon to seal airbox?

    Also, regarding the in tank line. Could it be soft enough to collapse on itself when running?
     
  8. Okie

    Okie ArboristSite Guru

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  9. mogulmasher

    mogulmasher ArboristSite Lurker

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    Cool, I'll double check what I used for fuel line size, but it was a nice tight fit. I used a small zip tie on line just inside of barb. This has always worked well for me on sleds. With a decent tug and/or twist line doesn't move. I have various sizes of tygon fuel line for sleds and the OD just wasn't big enough.

    My saw uses a vented cap.
     
  10. mogulmasher

    mogulmasher ArboristSite Lurker

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    Well I confirmed the fuel line I used, 3/16". I looked and I only have 3/16", 5/16" and 3/8" on hand so I didn't throw 1/4" on it after all.

    I started it up tonight and tuned carb as you suggested, and guess what? It runs! Obviously haven't put it to wood yet to finish tuning but it runs right up and now and still idles great. Can't believe this got it running, the low jet litterally ended up probably only 1/8 turn richer.

    Can't wait to put it to the wood and make sure it's all good now.
     
  11. Brent Nowell

    Brent Nowell ArboristSite Member

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    Randymac I recently acquired a super pro 60 all yellow with no chain brake and an auto/manual Oiler
    I know very little about it and was wondering if you could tell me if it was designed for heavy duty use or reliability? Was it a good model for its time? How does it compare to 60cc saws today?
     
  12. Okie

    Okie ArboristSite Guru

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    Eventually if you are going to be using the saw for felling a tree find yourself a spike saw dog.

    Don't need the spike after the tree is down due to the weight of the old Mac's, but when the saw is sideways felling a spike really helps
     
  13. 2broke2ride

    2broke2ride ArboristSite Guru

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    Post your question in the mac thread. But yes, pretty much all of the macs from that era where considered pro grade saws.
     
  14. mogulmasher

    mogulmasher ArboristSite Lurker

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    I don't do a ton of tree falling, mostly have saws for bucking firewood. But if I do drop one would probably use my 6401 or the pm700.

    Wanna put felling spikes on it anyways though cause they look really cool!
     
  15. Okie

    Okie ArboristSite Guru

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    Yep, look cool, but you have to keep a heads up with the old Mac big tooth cool sharp spikes they will take a bite of meat out of the OP easily, especially if stumbling along carrying the saw. If they get a good bite/gouge into your leg the first time, you will not forget such again when you pick up the saw.:surprised3::eek:

    I also only do not use the Heavy Macs for felling very often, but when I do the spikes are a good thing to have on the saw.
     
  16. RandyMac

    RandyMac Stiff Member

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    dog in for bucking, make that saw work, they were made that way
     
  17. mogulmasher

    mogulmasher ArboristSite Lurker

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    Well I put the 1-52 into some wood today. Saw ran great, still could use some fine tuning on the high side. Even did some noodling with it, cuts good. 20180715_182154.jpg
     
    2broke2ride likes this.

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