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Thread: Top end rebuild woes

  1. #1
    apriliaforum newb Russell M's Avatar
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    Top end rebuild woes

    So I decided to do my top end rebuild in frame this time on a different bike. I've encountered a new problem this time too! I have removed all nuts from the cylinder studs, removed the exhaust from port and slid out of the way. I have broken the gasket seal and the cylinder has about 5mm of play in it. It WILL NOT move any further, obviously lifling straight up, I can not figure out what's stopping it.

    I did notice this time around that one of the cylinder studs had a 13 mm threadlocked nut on it whilst the other 3 were 11mm, I don't recall that from the last build but who knows.

    Any ideas what might be causing my cylinder to not move?

  2. #2
    apriliaforum Junkie rs125-700's Avatar
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    Where is the piston?
    the rings might be catching on a port, put the piston at TDC. Make sure the barrel goes straight up, carefully lever the barrel upwards (are all the bolts undone? (especially the crossmember that attatches to the top of the barrel, assuming it is the 2 stroke and not the shitty 4 joke)
    (the rings in the normal stroke of the piston are unable to catch the port, as you remove the barrel the rings can snatch, thats why putting the piston at tdc as high as it will go can make removal easier)
    Early bikes had 11mm nuts, Aprilia (piaggio ) have obsoleted the 11mm nuts and replaced them with 13mm which are hard to undo and torque up.
    https://www.pjme.co.uk/acatalog/Apri..._Top_End_.html
    pjme list the 11mm part and will charge you 5.40 for your trouble (top of the page)

    good luck
    Last edited by rs125-700; 04-07-2019 at 05:33 AM.

  3. #3
    apriliaforum newb Russell M's Avatar
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    Alright so upon somewhat successfully completing the top end rebuild i finally got round to filling the coolant, almost as soon as I started pouring the coolant in, it started pissing out the crankcase at every gasket point and even the cylinder gasket to a lesser degree. What on earth is going on? I used the best quality gasket I could get, tightened and checked every bolt twice, used a dab of grey silicone and I'm a little concerned to see the volume of coolant exiting. The bike wasn't leaking coolant previous to the rebuild, definitely not from the crankcase.

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