For those of you who have experience of ordering replacement big end shell bearings to fit a 900ss 1992, and suchlike, There is conflicting advice to get the Ducati specified oil-film gap; some experienced Ducati re-builders on the web say say a mixture of one blue , one red to each journal. Some say they usually find the get a better fit with two blue bearings to each journal. They don't seem to mention whether their crank journal has been ground or not, or by how much. All online catalogues seem to offer only 'red' as standard size crank shell bearings. The thickness is not given. They correspond to the part number 112.1.001.1A, which is what I find etched on my existing (to be replaced bearings). The same catalogues offer -.25 and 0.50 undersize, but give no colour code to those. Q Do you know whether there are alternatives for standard size crank journal - coded as colours and/or thickness? Or, are those builders speaking about undersize grinds? cheers, John
When I had a 748RS rebuilt into an 853, I supplied a set of red shells and a set of blue shells. No regrind of the crank was neccessary and I got the a complete set of the one colour shells back (without looking I think it was blue). Never got my head around cranks, barrels and pistons that came in 'A' or 'B' which I think is a tighter upper (A) and lower (B) tolerance within the overall tolerance ..... maybe Andy
Thanks Andy. That goes a long way to confirming my what I suspect to be true. Red plus red for a 'standard' size non re-ground journal is all that should be necessary.
That's what they say. E.G. 'BradtheBikeBoy' on ducati.ms and others. I have problems with that though; like, are the two different thicknesses matched for roundness; if for made for undersize journals, I dont see how they can be. And, I dont beleive it now, for journals that have not been ground - it should not be necessary, unless selecting from a range that is working to match within manufacturing tolerances. That's clearly not what's on offer. The colour code thing is still puzzling, because I only see standard 'red' on offer for the 900ss and also undersize shells (at a considrably higher price, for the strangest reason I cannot imagine); perhaps the other colours are designated for other models with 'A' type conrods fitted as standard. In which case these builders are suggesting mix with standard bearings from another model. I dont know how they know what they are doing, unless the conrod and cap is specified... well, all relevant specs. I'm now going to simply put it aside and ignore their advice as insufficient, and order two standard 'red' as offered by the catalogue, with some greater confidence. I will take a gap measurement for the record.
Blues and Reds aren't the only shells, they're just the common original sizes. Ducati also make and sell Yellows, Greens, Blacks etc, but you need to go into the race parts bins like the 996RS to find them. EVR who also make dry/slipper clutches sell under size shells for journals that need re-grinding, Ducati used to but don't any more I don't know why? You need to accurately measure the big end journal, I use "Plastigauge" with either Blues or reds and then select the shells to give you the required clearance. The 916 crank in my 851/916c ran 2x's Blues, the modified 916SP item in my 851/955cc runs 2x's Blacks. It IS ok to fit one blue and one red to a journal if that's what's needed to set the correct running clearances. The differences between the colour code/steps is in microns as in smaller than 1 thou. Steve R
