Right cylinder blue smoke on an R80/7. Oh dear...

Discussion in 'Airheads' started by Blackburn Buccaneer, Feb 27, 2019.

  1. Blackburn Buccaneer

    Blackburn Buccaneer Been here awhile

    Aug 5, 2018
    North Sea rim
    Quick update:

    So the top cylinder studs were completely gunked up with some sort of silicone rubber stuff. That might explain why the heads were shot a year after they were rebuilt by the PO. At least now I know that he didn't lie about the top end being completely redone a little over two years ago

    Cylinders and pistons are in great shape, cam followers are brand new and the con rod also feels perfect. Still put the siebenrock power kit on regardless, I'll be selling the old jugs. Took a few hours, but it all went pretty well. No real problems along the way , but why in the name of all that is holy has Siebenrock gone with the older style gudgeon pin circlip is beyond me. Pain in the fucking ass to get those in.

    Tomorrow I'll fire it up for the first time in 5 months!
    Cogswell, Jim K in PA and Square1 like this.
  2. tsADV

    tsADV Been here awhile

    May 28, 2014
    Telemark, Norway
    I think that's because the gudgeon (or wrist) pins they supply can then be shorter, and that results in a major part of the weight saving their pistons offer, compared to standard BMW pistons.

    And don't complain about fitting the Siebenrock pin circlips until you have tried to fit circlips for model year 1977 BMW R100RS pistons . . .
  3. bmwrench

    bmwrench Long timer

    Nov 10, 2006
    Just one of the reasons these were designed. No more evil internal circlips, available in "hone-up" and oversizes, lighter than stock, and with the proper squish band.