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

Blaze_Fox89

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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. :(
 

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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.
 
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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. :(
 
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?
 
oil on the shaft and the outer edge of the seal

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.
 
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.
 
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).
 
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.

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

66cc.

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 :giggle:
 
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