Mag side engine seal.

Discussion in 'Motorized Bicycle General Discussion' started by breno, Aug 27, 2010.

  1. breno

    breno New Member

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    Well was I doing a little maintenance today and noticed on inspection that the mag seal must be leaking I found about a teaspoon of oil in the bottom of the Cover/housing. Is there any trick to undoing the 14mm nut to pull it apart to get to the seal??
    I tried pulling on the brake and undoing it but it felt like it wasnt going to come undone easy enough before something else was to give way. Whats the method?
    Thanks in advance fellas
     
  2. killercanuck

    killercanuck New Member

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    Hey, here's a little trick my dad taught me along time ago...

    Get a small piece of rope or thick wire, pull your plug, turn until you're about 'bottom-dead-centre', insert a good foot or so of the rope/wire into the plug hole, keep out enough so you can pull it back out when you're done!

    The rope/wire will keep the piston from 'cranking over' and allow you to loosen any crank nut.

    Oh, and when pulling the rotor make sure you mark which side is 'out' with a scribe or marker or something. If you put it back in wrong, you'll mess up your ignition timing!!

    gl.
     
  3. breno

    breno New Member

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    Thanks bud!! lol my luck I would drop the bloody rope in all the way in..
    Cheers for the tip. But is this the way ppl normally do it?
     
  4. killercanuck

    killercanuck New Member

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    Oh, btw, you're lucky it's only your seal leaking. A little while back, my engine wouldn't start after a good cruise across town(had to peddle her back :( ), but anyway, when I got my rotor off, this is what I found:
    [​IMG]

    A nice little casting imperfection peeing gas all over my magneto. A bit of Goop in there and I was good to go again.

    I've read the seals can(and do) pop out occasionally, hopefully that's all you have to deal with.

    gl, again. :)
    cvlt1
     
  5. killercanuck

    killercanuck New Member

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    Cheers! Its an old lawnmower trick, instead of putting a screwdriver in the vent splines and snapping a couple, heh heh.

    (I posted the pic while you were posting, D'oh!)
     
  6. 2door

    2door Moderator
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    Impact wrench. The quickest and easiest way to loosen that nut. If you don't have access to one then put a socket on a ratchet and smack it with a soft head hammer.
    Once the nut is off the next challenge is getting the magnet (rotor) off the crankshaft. Here's where you'll want to be careful. The crank is only about 5/16" in diameter where the rotor rides and it can be bent if you pry too hard on one side of the rotor. There is a woodruff key and sometimes it can give you problems getting the rotor to come off. I've found the perfect puller for the rotor in a faucet handle puller tool from Ace Hardware. It is thin enough to fit behind the rotor and pulls it off easily. After the rotor is off check the seal behind it. Its not uncommon to find them not seated correctly in the bore. If the seal is not damaged or worn you might be able to press it in until it fits flush or the better route is to replace it with a new one. Many of our sponsors carry new seals. Use a socket just a shade smaller in diameter than the seal and drive it in until it is flush with the case. Lubricate the new seal and crankshaft with engine oil before assembly. Good luck. Let us know how you make out.
     
  7. breno

    breno New Member

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    Thanks for the tips guys. I ended up using a battery powered rattle gun and she came straight off. I was fortunate enough that the mag pulled straight off after i marked it to ensure it went on the same way. Seal wasnt completely seated it was out about
    1-2mm. The socket and rubber mallet made light work of tapping it in all the way.
    I used electrical contact cleaner to get rid of the small amount of metal debree around the housing and everything else within. And blew it out with high pressure air. Reassembled now I just gotta wait till i finish work to give it a ride. I have to ride 37km to and from work everyday so its fortunate I work in a plant with plenty of tools lying around. I took a look at the rear sprocket today and noticed that just about all the nuts had came loose. And 3 of the spokes were so loose they were bending. Ended up double nutting all the bolts so hopefully thats a problem a may have prevented for the future. Far out these motors can be hard on bikes. Atleast I know what to check after each ride now. Thanks again for all the help.
     
  8. breno

    breno New Member

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    You must have been pi$$ed when u sore that hole... chinese crap. Are well looking forward to the first rebuild to match port and get rid of any dags I can find and it should finish up to be a pearler of a motor. As i read somewhere b4 they are cheap coz they dont take the time to clean'em up nicely or something along those lines
     
  9. killercanuck

    killercanuck New Member

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  10. breno

    breno New Member

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    Far out tha 2nd vid scares me. I bought the 70cc skyhawk 3rd vid looked alittle more promising.
    Cheers for the link mateauflg
     
  11. breno

    breno New Member

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    Well last night after getting home pulled off the mag cover to find a small puff of smoke and about half a teaspoon of oil. DOHHH!!!
    Ive got a new seal already its the doulle edged type.
    Is the best way to pull the seal out with like a hook pin or something like that??
    When fitting the mag seal I read somewhere its a good idea to pack the bearings with abit of grease. Is the trick to leave the outside of the seal totally dry but add a little grease to the shaft so it slides in easy?
    Or no grease on the seal at all?
     
  12. 2door

    2door Moderator
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    Its always a good idea to lubricate the new seal and shaft before installing. No sealer is required on the outer edges of the seal but some smear a little silicone gasket sealer on it. I don't. Be sure to get the new seal perfectly centered before driving it in and yes, the old seal can be removed with hooked tool. Be careful and don't damage the sealing surface of the crank where the seal rides. It needs to be smooth. Good luck.
    Tom
     
  13. breno

    breno New Member

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    Thanks again for your help Tom. I look forward to giving it ago..
    The gasket sealer doesnt sound like too bad of an idea but whats the cons with doing it? As you said you dont do it yourself

    Cheers mate appreciate your help
     
  14. 2door

    2door Moderator
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    Any material other than oil that gets on the sealing surface of the crank and seal can shorten the life of the seal. The outer surface of the seal is rubber and fits snuggly into the bore. Installed properly you really don't need the extra assurance and the seal stays clean.
    Tom
     
  15. breno

    breno New Member

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    that makes good sense cheers mate I'll take some pic's of the process and post em up in this thread as abit of a how to might make it easier for the next person that comes along..
     

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