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What's the easiest way to trobleshoot for bad crank seal

Discussion in 'Chainsaw' started by 028AV Super, Apr 30, 2007.

  1. 028AV Super

    028AV Super ArboristSite Member

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    Hi everyone,
    Quick background on the saw. I just went through my 028AV Super, replaced piston/ring for scoring, carb kit, all the rubber hoses, filters, muffler mod, and down sized to a 16" from 24". Got the saw running with no problems. One nagging problem is the saw bogging down under a load which I had prior to freshing up. Started out with 1 1/8 on low, and 1 on high which started after 4 pulls. Did WOT adjustment according to this site experts.

    The saw starts easy but at times very hard. Sometimes pull cord locks up (painful when drop starting...). I did notice some rubbing marks on the flywheel with the mag pick-up (possible play in the crank from worn seals or bearing?). Didn't notice any excessive play on the flywheel side. Also noticed the carb spit-back quite a bit more than before. Jocking the throttle without load varies from nice quick transitions to bogging at times. I did rotate the saw 90 degree each way while running and didn't kill the saw. Without performing crank case vacuum/pressure test, is there any easier test. I've heard about spraying WD-40 behind the flywheel? I guess this means after you get the saw started, take the cover off the expose the flywheel?

    At this point, I was just thinking about replacing it anyway. I read about the knot on small rope trick to lock the cylinder to losen the flywheel nut (left hand threads). My concern is the clutch side where special puller is needed. Any recommandations on the tool issue? Any tips on getting the seal out without spliting the case (hoping for good bearings)?

    Thanks for your inputs.
     
  2. huskydave

    huskydave Addicted to ArboristSite

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    The easiest way to check for worn seals or vacuum leaks on any small engine is to spray carb cleaner around the crank or the carb boot if there is one.On a chainsaw this could be dangerous I would get someone to hold down the saw on a bench and at idle spray the carb cleaner in behind the flywheel. If the rpms rise you have bad seals.This is just one way of doing it others may have better advice.
     
  3. 028AV Super

    028AV Super ArboristSite Member

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    Thanks Dave!
     
  4. troutfisher

    troutfisher Addicted to ArboristSite

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    I have heard that you can fill the crankcase with transmission fluid, and watch for leaks around the crank seals. I have never tried this, but it sounded good.
     
  5. West Texas

    West Texas AboristSite Guru

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    I've only had to replace a seal once, and how I detected it as a problem was to start the saw, let it warm up and idle a while; then turn the saw on its side and listen to the engine speed. If there is a difference in the engine when you turn it on either side, I was told its an indication that the seals are bad. In my case, that is exactly what happened; there was a noticeable difference in the engine when I turned it on one side. I replaced the seal and it has run great ever since. Getting the old seal out is the neat trick; putting the new one in was a piece of cake.
     
    Last edited: Apr 30, 2007
  6. Hard Knocks

    Hard Knocks ArboristSite Operative

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    You might want to pull the flywheel and check the flywheel key. I have seen flywheel keys shear and knock the timing out just enough to make the saw act up. some of the symptoms can be kickback/lockup when pulling it over, and spitting back through the carburetor.
     
    Lou likes this.
  7. Lakeside53

    Lakeside53 Stihl Wrenching

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    Lots of ideas above, and not trying to stifle suggestion but... a couple of point from the above posts

    - Flywheel keys don't tend to shear in this type of saw. They are hard tool steel on a long taper crank stub.

    - No special tool is required to remove the clutch on an 028 - it's the flywheel side that requires a puller. The flywheel side nut is NORMAL thread.

    - spraying carb cleaner around seals is almost impossible and real dangerous... never mind the mechanical difficulties of getting it to the correct place behind the flywheel, but the risk of fire is very real. Also, it will tend to kill a saw (richens), not raise the rpms. 028's are much more likely to have a bad clutch side seal anyhow.. and you can't even get close to that unless you run the saw without a clutch.

    - filling the crank case with fluid wont do anything unless you have a complete seal failure, and in which case it real obvious - the saw will not start or if it does, wont idle. Seals are often great on pressure, but just fail under vacuum. So far you description of problems doesn't sound like seals.


    Back to the question at hand... The most obvious indicator of a seal leak (not a seal failure) is inconsistent idle and difficulty starting. If the carb needles are more than a 1/4 turn away from standard setings to the rich side, then you are likely compensating for an air leak somewhere.


    You don't have to split the case to replace the seals, but they can be tricky to get out without the correct seal pulling tool, particularly on the flywheel side. Insertion is easy - grease the lips, and use the correct size socket to tap them in. The clutch side has a shoulder that will require you to either use wraps of foil to allow the seals to side on the crank without popping the spring, on or a crank sleeve tool.
     
  8. stihltech

    stihltech Addicted to ArboristSite

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    ok, here we go.........

    Number one, Lakeside is correct on all accounts. This is the only correct way to check seals, pressure and vacuum test.

    Being a little backyard, and looking for a quick diagnosis, WD40 and a long straw works best. I only do this on a saw that appears to be not worth the time to diagnose or repair, or if the customer really wants a new saw. I never tell the customer he is wrong, in this instance.:greenchainsaw:

    And yes, it will either get rich, or stop.
     
  9. 028AV Super

    028AV Super ArboristSite Member

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    Wow, good tips from everyone! Thanks,;)
    I'll tear in to it once I get a set of seals. I'm going to try a harmonic balancer puller on the flywheel. I guess I would have to see it how both side comes out during the disassembly. I remember reading on the forum about blue (Stihl) color seals are better than black (after market)?

    Can anyone tell me the cost of Stihl special tools for this job? How about a suitable sub from common tool box?

    Either way, the crank seals replacement are the only thing left on my saw to change.

    Again, thanks for all your help!
     
  10. 028AV Super

    028AV Super ArboristSite Member

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    Thanks Andy,
    Have you seen any bad crank roller-ball bearings on these saws? Will a bad crank oil seal on the flywheel side cause radial play during starter rope pulling to cause flywheel to contact the mag pick-up? I set the clearance last year with a matchbook on both blocks on the wheel.
     
  11. Lakeside53

    Lakeside53 Stihl Wrenching

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    Take your saw to your stihl dealer and have them pop the flywheel - it's a 10 second job if you have it prep'ed. Using any other type of puller runs the very real risk of damaging your flywheel.


    Flywheel puller is about $20 in Ebay stores. Maybe cheaper from your dealer. The seal puller is damn expensive... Like $125-140...
     
  12. Lakeside53

    Lakeside53 Stihl Wrenching

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    Bad bearings are rare in 028's, but they happen.

    It would have to be really bad... and if it is moving it's most likely the CLUTCH side that's shot causing the flywheel side to pivot in the flywheel side bearing. Your coil might have moved - you're supposed to use blue loctite on the coil screws.
     
  13. MS-310

    MS-310 AboristSite Guru

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    Could you run the saw without the clutch on to check with carb clean?


    I got the crank seal for my 088 today and I got it all tore down to put it in!!!!
    the seal that is in it, is new........SO thats why I want to check it.....sorry to ask my ???? in your post
     
  14. Lakeside53

    Lakeside53 Stihl Wrenching

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    I would never put carb cleaner on a seal. WD40, yes, but carb cleaner.. no...

    Yes, you can run it without a clutch, but... carefully, and I don't bother. If it went in fine and you greased the lips first, it will work. You'll know on starting if it's bad anyhow... use a torque wrench to put your clutch back on.

    Two things

    - Make sure you inserted the seal so it was just level with the top of the bearing. If it's too deep it will rub on the center hub and burn up or wear out.

    - Visually inspect the seal with a magnifier - make sure the center is not puckered up or irregular in any way. If it did push up when you tried to insert it, the spring on the back may have rolled off. Such fun...
     
  15. manual

    manual Banned

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    I just made a fly wheel puller, Not bad eh.[​IMG]

    could you take some pics of the seal puller ?
     
  16. Lakeside53

    Lakeside53 Stihl Wrenching

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    Nice.. Now make a set for stihls :biggrinbounce2:


    Here's the seal puller... reverseable jaws for 6 sizes, plus the little white plastic jaws for 200T seals. Technique sensitive, but works great.



    [​IMG]

    [​IMG]

    [​IMG]


    Just for interest, what does Husky or Dolmar supply or recommend?
     
  17. manual

    manual Banned

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    Hmmmm,Thats do able what is the width of that ? hinge pin to hinge pin ?
    I don't know what husky sells.
    I just ordered the oil pump gear puller for the 262's cost just under 10 bucks.
    and thats just the part you screw on the gear that is pressed on the shaft.
    I am still waiting for it to come in.
    What I have been doing is drilling two holes in the seal using a magnet to keep the shavings out and then I made a small slide hammer to pull the seals out.
     
    Last edited: May 1, 2007
  18. 04ultra

    04ultra "Out of Control"

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    Andy some guy just bought a stihl puller like yours and mine on sleezebay for mid 200.00's used.....



    .
     
    Last edited: May 2, 2007
  19. manual

    manual Banned

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    Wasn't me. LOL
     
  20. 028AV Super

    028AV Super ArboristSite Member

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    Once again Dave, you are the man! Thanks,
     

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