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Messing with my Aprilia Cup

Discussion in '2-Stroke Machines' started by Mike Fennell, Apr 19, 2024.

  1. Mike Fennell

    Mike Fennell Never Was

    Small world department. My brother in law's girlfriend's brother works for Aprilia and has since the Cup days. He thinks there's a good chance he actually had hands on my bike back in the day.

    Still paralyzed about pulling the crank. :) I put a puller on the flywheel ('magneto rotor'), then chickened out when I started to worry about how much force I was using. I think I have a spare. I should just send it.
  2. Mike Fennell

    Mike Fennell Never Was

    Progress continues at my glacial pace. Installed spools. Helicoil on one side, tapped out the other (the one that had a bolt broken off in it). Lots of patience with the drill.

    Always finding something. I hadn't noticed the missing seal on the shock linkage, inviting extra dirt and moisture in there.


    Took me forever to find my big boy pants and split the case, which I did this morning. The magneto was a bitch and took a scary amount of force to break free.

    I think the manual showed a tool to split the cases but there are two handy castings to let you press them apart. I ground down an M8 nut to maximize area and threw in a washer at the base to hopefully not crack anything.


    And voila. I should have removed the clutch drive gear before the magneto. I couldn't get a good grip on it while still assembled.


    Some coolant dribbled out from the case halves. I assume it made its way in when I was removing the cylinders.

    I haven't found anything obviously wrong yet. Subtly wrong, I'll probably miss. Probably even odds whether I'll get this thing back together properly. :). I should start pre-funding Steve so it won't hurt so bad later.

    I guess I'm crazy to go this far and not pull the trans, right?
  3. motion

    motion Nihilistic Member

    2nd gear is a known weak spot. I got launched in Turn 1 at Willow Springs at 100mph when my 2nd gear exploded.
  4. Robin172

    Robin172 Well-Known Member

    It has helical primary drive?
  5. Mike Fennell

    Mike Fennell Never Was

    I found 1/2 a gear in the transit case that came with the bike. Assume it was 2nd. The belly pan was full of oil so I'm guessing the carnage was substantial. I haven't actually pulled it out to see.
    motion likes this.
  6. Mike Fennell

    Mike Fennell Never Was

    Yes. Straight cut is available and someone suggested I get it but that's really going over the top for this bike. I've already been convinced to but a new crank.
  7. motion

    motion Nihilistic Member

    A new crank will give you about 3K of race miles, so good move.
    motosapien likes this.
  8. Mike Fennell

    Mike Fennell Never Was

    So basically the rest of my life. I strive to make 10 track days/year and I'll have two track bikes. :)
  9. SpeedWerks Racing

    SpeedWerks Racing Well-Known Member

    Sharath has a stack of em pretty cheap. @motosapien
    motosapien and Mike Fennell like this.
  10. Mike Fennell

    Mike Fennell Never Was

    He's sending one to Ed Toomey for me.
    motosapien likes this.
  11. Mike Fennell

    Mike Fennell Never Was

    Noticed what look like cracks in my lower crank case. Checked my spare and it looks exactly the same. They appear to extend to but not breach the bearing surface. Has anyone seen this before?

    Some Facebook posters think I could just be seeing casting flaws. Suggest liquid penetrant testing or even x-ray (@motosapien has many cool tools at his disposal).

    Engine I just took apart:


    Spare engine with locked up transmission:

  12. motion

    motion Nihilistic Member

    Yeah should be just casting marks. I've never heard of a case cracking.
    Mike Fennell likes this.
  13. Robin172

    Robin172 Well-Known Member

    Lightly rub the area with very fine emery, if they're casting marks they'll buff out.
    motosapien and Mike Fennell like this.
  14. Mike Fennell

    Mike Fennell Never Was

    I like you guys because you tell me what I want to hear. :beer:
    freedomgli and motosapien like this.
  15. motosapien

    motosapien Well-Known Member

    Use a low viscous penetrant dye used to check for cracks in metal at the location before rubbing with emery paper. This will help you differentiate b/w casting flaw vs fatigue crack

    Mike Fennell likes this.
  16. Mike Fennell

    Mike Fennell Never Was

    Pulled the spare trans out of my second engine to see if anything was salvageable.


    Not so much. The hole is above the oil injection pump so it's not obvious from the outside. The trans was locked up. Someone had a very bad day (like @motion did).

    Hung some parts on the frame mostly to get stuff out of boxes/off the floor. I was about to order a Brembo RCS17 MC when I realized the brand new brake lines I just bought were not compatible. My MK1 has a radial MC, so the brake line works up top but it's the older style calipers with a different fitting angle. Somehow that was a bridge too far so I just put the stock one back on after flushing it out and replacing the reservoir.

    sharky nrk and freedomgli like this.

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