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NSR Cylinder Nuts Problems - 2 Stroke Top End Rebuild

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Morbo28, Jan 14, 2009.

  1. Hi all,

    I have both the new parts and the mechanical aptitude to do a top end rebuild on my NSR150SP.

    However, I have come across two issues before I really even began.

    1. One of the cylinder head bolts is rounded. I tried to under it with quality tools but it was too far gone. It's gunna be a pain in the arse. But I will be able to get around this somehow...the main problem is:

    2. Even after this is dealt with, the nuts that hold the actual cylinder sleeve onto the bottom end (see pic - nuts are circled) are recessed in. But there is not enough room to fit a socket over them. A ring sanner does not fit over them. In fact it is damn near impossible to use an open ended spanner, as even if I get it on, the 'shoulder' of the spanner end fouls the cylinder preventing any real movement. I could take a grinder to an open ended spanner, but there must be an easier way.


    Any ideas?!?! Or has anyone that has worked on these before able to shed light on how they do it?

    I just didn't even consider that this would be an issue...wtf? It's an easy bit of maintenance, but what a stupid bloody design that causes these problems? Or am I missing something.

    Also, this means that though I will torque the head down properly, the cylinder itself will be guess work it seems.

  2. From your picture, the cylinder appears to be very similar to a RS125GP cylinder.
    A 1/4" drive socket will fit and a long 1/4" extension clears the side if the cylinder.

    BTW, the nuts shouldn't be that tight that a good quality 1/4" drive won't be able to handle it
  3. Hey, cheers for the reply!

    I just took the bike for Anthony's (the mechanic at MotoHeaven) opinion. He's worked on the RS125 engine and actually mentioned that there is heaps more clearance on those.

    The 1/4 drive socket just wouldn't fit on, except at a mean angle, that is really too dodgy to use. He loaned me a long socket (that doesn't widen so soon) and even that was at too much of an angle.


    I managed to get a way better quality ring spanner, one of those slimline ones. It JUST fits in the gap required, and just undid the cylinder bolts! :woot:

    Also, just used some vice grips to get that other crappy nut off, and managed to find some exact same replacement ones, so will use those on all of them when I put it back together.

    And as you say, the nuts were WAY too tight. As a test, I torqued one of them back up to spec and it was significantly less tight than the others. That contributed to it being a bit more of a pain in the arse.

    This is the new ring spanner sitting next to a standard spanner. Note how much slimmer it is. It's also 12 inches long so has a good amount of leverage.

  4. I love a happy ending.
  5. i took a grinder to my spanner when i did the smae thing