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rear hub nut removal on PX150E

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PX150E in ZA Gerrit Burger
Cape Town, Western Cape, South Africa   ZAF
I'm struggling my butt off to remove the rear hub nut on my PX150E (year 2000 model) to replace the leaking oil seal on the drive shaft.
Is it perhaps a left hand thread ? Difficult to see, but close inspection has just shown that it may indeed be the case. If so, I have by now succeeded in really tightening that nut !
But why doesn't Haynes workshop manual warn about this ?
Any information will be appreciated.

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PX150E in ZA Gerrit Burger
Cape Town, Western Cape, South Africa   ZAF
Just an update on my struggle with the rear hub nut.
I received assistance from an experienced amateur Vespa mechanic living around the corner from me. He owned a Vespa himself and had rebuilt several Vespas as a sideline.
With his help we found a way to loosen the axle nut (which was indeed very tight, inordinately tight it seems). Using a suitable length of sturdy pipe, you place one end against a wheel stud with a nut on it to protect the thread. The other end jams against a bolt on the swingarm cross member. (See photo attached.) In this way, and with a hefty extension on a T-bar, the nut yielded. Oh and incidentally, it had normal right hand thread all along ! The hub was eventualy prevented from rotating in the same manner for the purposes of tightening the axle nut.

When the brake drum was removed, it transpired that the axle bearing just behind the backplate was a sealed bearing which had NOT been leaking. So, no leaking oil seal, in fact, no oil seal apart from the seals forming part of the bearing.

It was therefore not gear oil which had leaked and created the unholy mess on the back of the scooter. (The picture shows some of the gunge left over after several hours of cleaning.)
Further investigation revealed that the union nut on the end of the tube bringing two-stroke oil to the oil pump next to the carburettor had become loose, allowing oil to leak into the carburettor housing, and from there past the grommet for the idle adjustment screw onto the back of the engine. The turbulence created by the spinning rear wheel did a good job of spreading the mess over the adjoining region. The oil pump was taken apart and inspected, the carburettor was opened and inspected and no wear was detected (at 46 000 km). New gaskets were cut for the carb and everything was re-assembled. While we had the carburettor box off, the starter motor was removed, opened and cleaned up. Burned contacts were found in the wiring connector on top of the fan shroud, and replaced.

Now I have a scooter again that goes like a new one, starts instantly, and keeps its rear end sparkling clean. Suddenly the world seems a much better place.


Attachments:
vespa axle nut.jpg    37.4 KB
vespa axle nut.jpg

OlympiaScooterCompany Avatar
OlympiaScooterCompany Matthew Gatlin
Olympia, WA, USA   USA
Just as a FYI for future riders who face this issue, if you leave the rear tire on when trying to remove the hub nut, this will make the removal much easier.

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PX150E in ZA Gerrit Burger
Cape Town, Western Cape, South Africa   ZAF
You are absolutely right Matthew. I also thought of that and did in fact try it (before calling on the guy around the corner from me). But the scooter simply walked forward as we tried to loosen the nut. Remember that the rear brake linings were soaked with oil and i was hesitant to put it in gear for fear of damaging something in the drivetrain.
Incidentally, Haynes' Workshop Manual specifies 65 -- 80 ft lbs of torque on that nut. I think this fairly high value, plus the fact that the nut was undisturbed for 18 years, was the reason for its stubbornness. A mystery to me is why such a high torque if it is secured with a split pin anyway ? A discussiion ensued here whether a split pin can be sheared by an under-torqued nut. Have you ever seen it ?

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OlympiaScooterCompany Matthew Gatlin
Olympia, WA, USA   USA
No sir, I have seen a loose nut rotate and bend the cotter pin slightly, but have never seen one that sheered off. - Glad you were able to get it off bud - see you on the road smiling smiley



Edited 1 time(s). Last edit at 2018-03-27 09:18 AM by OlympiaScooterCompany.

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OlympiaScooterCompany Matthew Gatlin
Olympia, WA, USA   USA
The irony is this post is that yesterday I ran into the same issue with a rear hub nut. I ended up applying an torch to the nut, and then used a long torque wrench (2 feet) to remove the nut.


Please note, we reinstalled the rear tire so one person could hold it as leverage to keep the hub from rotating while the other person worked the wrench.

PX150E in ZA Gerrit Burger
Cape Town, Western Cape, South Africa   ZAF
We also thought of applying a torch to the nut, but in the end decided against it because the brake drum is aluminium and we were worried about warping.
You obviously knew that before warping occurs, the nut will yield --- the advantage of experience !! There is no substitute for experience.
Glad you came right !

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