Oil seal ripped in half + idle needs LOTS of air.

Discussion in '2-Stroke Engines' started by Blaze_Fox89, Feb 12, 2012.

  1. Blaze_Fox89

    Blaze_Fox89 New Member

    I've searched and searched.

    First off, quick back-story. It is a zbox series 3 66cc, worked well, was run with only 40:1 once during break in and hasn't worked since. It didn't seize or overheat. Replaced everything except the piston, twice. Perfect compression, perfect spark up to 2mm, high tensile bolts, no major air leaks blah blah..

    Anyhoo, opened the carby half way to make it idle after it's third rebuild. It was working well but after 65km it started to idle poorly again, so I decided to check the oil seals and found that the inner part of the seal had ripped off and was partially eaten by the bearing.

    The only thing that I can think of is I used 2 stroke oil to lubricate the inner seal before putting them in and I used a spark-plug socket to seat it. This was several months before use.

    Are you supposed to put 2 stroke oil on the inner part of the seals (the face that contacts the crank) or leave them dry when putting them in?

    Any input or ideas on what happened/is going on is appreciated. I mentioned the low oil and piston stuff just-in-case it could be that too, the piston isn't scuffed what so ever. Sorry about the story but the next step for this motor is scrap metal if it doesn't run properly, I've tried and checked everything. :(

    Attached Files:

  2. motorpsycho

    motorpsycho Active Member

    My guess is that it's just a junk seal.
    the quality of these parts is not the best.
  3. Al.Fisherman

    Al.Fisherman Active Member

    First of I've never had a seal do that. Excessive compression will not do that, it will just blow by the crankshaft. It may be that the seal was installed improperly. Yes I lube the inner seal surface, and it doesn't make any difference what kind of oil you use, even a coat or wheel grease will be just fine. As far as the outer surface, sometimes I have to use a sealer like Indian Head gasket sealer, but only if I fear that the two surfaces won't match up as it should (but these seals have a outside rubber coating). Now for the crankshaft bearing...A number of bearings come from the factory with no seals, I recommend on the crankshaft you use a bearing with a outer seal, and on the clutch shaft a bearing with seals on both sides. As above, cheap parts might be the cause.

    Need air at idle = vacuum leak, which could be due to the defective seal.
    Last edited: Feb 12, 2012
  4. Blaze_Fox89

    Blaze_Fox89 New Member

    It's always had the needing lots of air problem just not as bad, I'm thinking it is the piston scuffing but not enough to leave a mark, it's a REALLY tight fit. I checked the seals and every place for air leaks, and the parts for zbox motors are the best, the same quality as grubees.

    The seal was also installed straight. I guess the oil must have dried up between the months of building and running. It must be just one of those small things, don't start your motor after recently changing seals and it might eat them. It did a lot of damage I can see bits of black coming up the transfer port, not good for any motor let alone something that's intended to hit 10-11k rpm. :|

    I will fit the new seal tomorrow if I am doing it right and try it out then and let you's know if it goes back to it's old terribly running self or eats another seal.

    Zbox motors are sometimes temperamental but I don't know of anyone who's had this much trouble with one. :(
  5. HeadSmess

    HeadSmess Well-Known Member

    ive popped seals from flooding the case and forcing it over. but never had one just chew out.

    oil on a seal at anytime is considered a bonus, so unless its some type of rubber eating grade of 2 banger oil, thats not it...

    when it comes to buying bearings with seals...theres a big difference between "sealed" and "shielded".

    i would NEVER put a double sided sealed bearing on a crankshaft.

    oil doesnt "dry up". grease can, but oil... even after sitting for 72 years in an engine, ive found oil tends to stay...oily.

    press them in with a close fitting socket, oil on the shaft and the outer edge of the seal, pressed square, with a press of some sort (drill press even), they should be fine.

    if you whack them in with a hammer, be careful?
  6. Blaze_Fox89

    Blaze_Fox89 New Member

    When you say that, do you mean the outer part that contacts the block? I've always just cleaned that area up real good and slotted them in dry.

    There's that then I tried turning over a flooded engine after that was where the problems started. Maybe instead of popping the seal out it just popped it and the clutch seal made it work. Those seals need lots of work to get out once in dry.

    I looked at the magneto seal and it's also looking like it's getting warn down, which is odd because it's new so I will put some oil on it just in case. I think what has happened is the oil is still there but it has slowly seeped away in to places. I will try it again and let y'all know how it goes in a few days, I have to put them in dry otherwise the boost pops them out just turning it over.
  7. Al.Fisherman

    Al.Fisherman Active Member

    Don't put the seal in dry. You can lube the shaft itself. Use some oil or grease around the shaft. Since the seal has a rubber like coating on the outside edge and if the case doesn't have burs on the seal service, no lube is needed here. If the inner hole of the seal is wearing down that quick then you have a problem with the shaft it seals.
  8. blue 48

    blue 48 Member

    ive always installed those types of seals using a good grease so the metal inner ring dosent fall out during assembly and it wont wear during a possibly dry first run so much (ie first start since assembly).
  9. Blaze_Fox89

    Blaze_Fox89 New Member

    Some things I have recently learnt:
    1. A zbox motor will hit 12000rpm with no load before destroying the top end bearing. (i gave it plenty of fair chances to work, don't complain.)

    2. Said destroyed motor will still get you to maccas and back as long as you rev the holy **** out of it.

    3. Said trip with said motor will be very unpleasant and noisy and your hands will go numb after a minute. the rest of you after 2.

    4. I will NEVER buy another zbox motor for a performance situation again, in-fact i doubt i would recommend them for a daily rider. I've seen so many that have been treated with care only for them to **** their bricks completely before 3000ks. Entirely unfixable, not even masking tape or gasket maker over new gaskets after everything has been washed leaving no oil what-so-ever. That's case gaskets, o-rings, all that shizz. And their metal quality has gone down even more and the storage area for the spare parts is damp, making everything rusty, i don't know if it's zbox or the factory, just be warned, there are quality issues.

    Just buy a **** grubee, there only AU$40 more. I'll get the name of the zbox factory for the rest of you outside of australia. maybe that might shed some light on the ****tyness of these engines.

    on that note, the seals held in after all that and didn't get eaten so i think grease is the go. 2 stroke works well if you turn it on in a week or so, it must have seeped into the rubber in the months it sat before being used.

    Thanks for everyone's help and sorry for being WAY off-topic for most of this post. just really really upset that after 14 months of solid work it still won't seal. :(
  10. HeadSmess

    HeadSmess Well-Known Member

    on closer inspection i can see the problem, all the way in your first post.


    thats my personal opinion, mind you.

    48's, always reliable...to a point. abuse seems to make them last longer than cottonwool treatment :)

    66...? if you aint got nothing nice to say :jester:
  11. Blaze_Fox89

    Blaze_Fox89 New Member

    i have plenty of nice things to say, i've just run out of nice things to say about zbox's. Anyhoo, grubee 66cc's work perfectly now, the gen 1-3 motors were prone to shattering their rod bearings but the new ones are flawless, makes me wonder why i switched. it was the grubee 66cc that i got to hit 92k's an hour. I think the problem is slightly cheaper metal and it has gotten cheaper now so it warps like crazy. if it was just my motor it would be fine and i'd shut up but it's 13 separate engines and counting that are unseal-able. i had someone offer me another one with the same problems the other day.

    There faygo union motors btw. i'll check the squareness of the case later on in the year.
  12. Blaze_Fox89

    Blaze_Fox89 New Member

    Thunder Update:

    I checked the crank cases on 2 motors I got a hold of and mine and they are sealing ok, just the intake flanges are severely warped but nothing unfoxable.

    My problem turned out to be a leaky headgasket that was leaking back into the crank case, making it run like it's rich and stall like an air leak (I checked it but there must have been something else wrong at the time). It still runs a bit rough and leaks air like a sive but it works well, I can probably recommend them now, but if it ever gets too hot, expect to have problems. They also sell rusty spare blocks and other things but their warranty covers that.

    So if you have a :poop:/dead zbox or an intake leak on something else, modern glass and what, 230-250 sandpaper? And you should be going again.

    The oil seals are holding well, even past 10k+rpm with no covers so this motor is shaping up well, finally.

    Apologies for the long semi-off-topic posts but this problem seems to happen to a lot of people (lean-like running with a black spark plug), so hopefully all this helps someone somewhat.
  13. Al.Fisherman

    Al.Fisherman Active Member

    Milling the head is high on my list of things to after unpacking the engine...along with others. Been recommending it for the past 3 years.
  14. Blaze_Fox89

    Blaze_Fox89 New Member

    The grubee and zbox motors have very good head seals to begin with so milling them would probably be bad as they have groves that bite into the seal, but cheaper ones definitely. This leak was caused by a de-threaded nut, but leaking internally. I'd definitely mill the zbox intake face and manifold though, they are all bad. The Grubee GTx's don't usually need anything done but the cheaper ones will probably need it.