SOHC.co.uk Forums > Project Board
Neils 1978 CB550 F2 Project - Newbie Let Loose
Laverda Dave:
Bryan or Nurse Julie can probably comment further but I am aware of the pistons failing on the edges like this as a result of previous owners ragging the engine before it is properly warm. You have likely caught it just in time, not sure if I would reuse them.
Bryanj:
Thats probably due to corrosion, worst one where valve was open, will run for a 2-3000 mile a year fun bike, not good for one used daily and/or hard.
You could rering it and hone but hone may give too big a piston clearance.
Piston kits or rings from cruzinimage in japan, std same price as oversize so you pay extra for rebore and then its as new if you wish
Neilw:
--- Quote from: Bryanj on February 10, 2026, 10:03:04 PM ---Thats probably due to corrosion, worst one where valve was open, will run for a 2-3000 mile a year fun bike, not good for one used daily and/or hard.
You could rering it and hone but hone may give too big a piston clearance.
Piston kits or rings from cruzinimage in japan, std same price as oversize so you pay extra for rebore and then its as new if you wish
--- End quote ---
I like the bike to run for probably less than 2,000 miles a year. I've broken the rings on 3 of the pistons, so you think I could get away with a light hone and std rings, keeping the pistons I currently have? The ones with the chips on the edge are a bit sharp, so can I just file those down a touch to remove the burr, or does that need to be replaced?
If i can avoid a rebore i'd like to.
When I removed the values, a couple weren't making a good seal, which I guess could be the cause. I'll lap those to improve things.
I'm new to all this, so I'd like to make a reasonable decision that gives me the best chance of having an engine without undoing everything. Your advice is greatly appreciated.
Nurse Julie:
You need to measure the bores to work out if they are still within spec to use those pistons with new rings. Personally, I would not use those old pistons anyway, I would have a rebore and fit a new oversized piston / ring kit. If you try and cut corners or do things on the cheap, these old engines have a habit of coming back and kicking you in the backside.
Neilw:
--- Quote from: Nurse Julie on February 11, 2026, 02:06:45 PM ---You need to measure the bores to work out if they are still within spec to use those pistons with new rings. Personally, I would not use those old pistons anyway, I would have a rebore and fit a new oversized piston / ring kit. If you try and cut corners or do things on the cheap, these old engines have a habit of coming back and kicking you in the backside.
--- End quote ---
Thank you, i assume i'd have to get a rebore on all the cylinders to keep things uniform?
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version