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1976 CB550F1 (what have I let myself in for) Project
Laverda Dave:
Have you tried swapping the oil rings around between the pistons? This will tell you if it's the piston ring gap not having enough depth or if it's the actual rings at fault. The 250RS piston I had a similar issue with was a pattern part from DSS. I can't remember the actual make but it was pattern but not IMD or Cruzinimage. I remember it was in a blue and white box though.
Laverda Dave:
I would also try swapping the outside pistons with the inside pistons for a comparison and to confirm if it's the bore or the piston at fault. I'd also swap the con rods over for the same reason. Obviously don't run it like that it's just for comparison purposes at this stage.
Bryanj:
You say 0.6 and 0.05 so total of 0.65 and if that is mm its over 20 thou or way to much.
OR are you measuring at crown not skirt.
Only reason i can think of for piston to be at angle is either bad piston machining or bored at an angle
Laverda Dave:
--- Quote from: Laverda Dave on March 01, 2021, 11:51:42 AM ---Have you tried swapping the oil rings around between the pistons? This will tell you if it's the piston ring gap not having enough depth or if it's the actual rings at fault. The 250RS piston I had a similar issue with was a pattern part from DSS. I can't remember the actual make but it was pattern but not IMD or Cruzinimage. I remember it was in a blue and white box though.
--- End quote ---
I meant to say ring grove depth not gap! Although interesting to see if the ring gap is larger or smaller if fitted to another piston but in the same bore.
eight0:
Just tried swapping 3 and 4 and the issue with centering doesn't go away.
Yes I mean I measured the crown above the top ring not the body, just to show how much is was pressed on one side.
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