SOHC.co.uk Forums > CB350/400
Barrels on but pistons won't move, what's going on. Help me !!!
billdn:
--- Quote from: McCabe-Thiele (Ted) on May 21, 2022, 10:06:07 PM ---
--- Quote from: McCabe-Thiele (Ted) on May 21, 2022, 10:04:51 PM ---I assume the new pistons were numbered from when the rings were gapped to each cylinder when it was bored out or have you done that part?
Not quite sure what you mean Ted?
It was a full rebore to +.25 and new pistons/rings to suit , would they need matching to each bore separately?
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McCabe-Thiele (Ted):
--- Quote from: billdn on May 22, 2022, 11:40:45 AM ---
--- Quote from: McCabe-Thiele (Ted) on May 21, 2022, 10:06:07 PM ---
--- Quote from: McCabe-Thiele (Ted) on May 21, 2022, 10:04:51 PM ---I assume the new pistons were numbered from when the rings were gapped to each cylinder when it was bored out or have you done that part?
Not quite sure what you mean Ted?
It was a full rebore to +.25 and new pistons/rings to suit , would they need matching to each bore separately?
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When Graham bored my block it was sent back to me with the rings fitted & the piston crowns marked with the cylinder bore with an ink marker. If you gapped your own rings then you would presumably match them as you went along. I'm assuming that in reality each piston will have a tolerance as will each bore so there will be clearance variation for each ring in each bore before you gap them imho. I'm not an engineer - I have found through experience with car engines that some rebores are not as exact as they should be. That's why I rate Grahams skill in this area. Sadly the place I used for cars as long since closed - Wylde Engineering in Derby were old school. Do you think the ring was bent when fitting the pistons,? I found that really difficult as you can't see or really feel what's happening. All my previous piston fitting on cars has been from the top
Hopefully the bore marks are not too deep and can be honed out.
Bryanj:
In 40 odd, some say very odd, years i have never had to gap a japanese piston ring.
I have had a scraper rail twist building a 1200 wing so it can happen to the best of us, dont feel bad about it, as long as the scratch is not too deep it will run, it al depends on what you realisticly want the bike to do
McCabe-Thiele (Ted):
--- Quote from: Bryanj on May 22, 2022, 10:37:43 PM ---In 40 odd, some say very odd, years i have never had to gap a japanese piston ring.
I have had a scraper rail twist building a 1200 wing so it can happen to the best of us, dont feel bad about it, as long as the scratch is not too deep it will run, it al depends on what you realisticly want the bike to do
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Interesting to read about never having to gap Japanese rings Bryanj
Bryanj:
Their QC seems to be good, to be honest never had to gap Hepolite either, as long as you ordered the correct size in the first place,
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