Cylinder and Piston Repairs - Nikasil Coated

Discussion in 'Technical' started by simonm, Nov 1, 2014.

  1. simonm

    simonm Member

    Hi,

    I have a DR250 Djebel and have been having problems with my piston/piston rings/cylinder. The local mechanic has told me I need to re-bore the cylinder and get a new oversize piston and rings.

    I'm concerned about this because the cylinder has a nikasil lining which would be lost if it was bored out.

    Out here having it re-plated with nikasil is not possible. Sending the cylinder to the US to be done is not practical or economical given the high age and low value of the bike so I'm going to have to make do without the nikasil plating.

    I've spoken to several mechanics. Some proposed boring it out and fitting a sleeve to accommodate a regular 73mm piston. Others suggested boring out the cylinder to take an oversize piston (and presumably no sleeve).

    I appreciate that neither is ideal as I will no longer have the tough nikasil lining. Can anyone suggest which of the two options I should go for?

    As I see it, it could make more sense to use an oversize +0.25mm piston rather than put in a sleeve as this would be less expensive and there would still be scope to further bore out the cylinder to +0.5, 0.75 and 1.0 if the bike is still running that far in the future.

    Am I right in thinking if/when the cylinder reaches it's max bore I could then fit a sleeve to bring it back to the original 73mm rather than fitting a sleeve now and every future time it is bored to keep it at a constant 73mm?

    Also, would a sleeve be more hard wearing or less hard wearing than the naked cylinder without its nikasil coating? If the sleeve would be stronger it may make more sense to use one and not have to re-bore the cylinder as often.
     
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  3. monsterman

    monsterman Ol'Timer

    SOme of the local ducati independents like Boy at chicane in bangkok may know of a local way to get a cylinder NIKASIL coated as he works over most of the local ducati race bikes here, but methinks UK, OZ or USA is best option ,,
     

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