SOHC.co.uk Forums > CB500/550
Pistons
Murf:
Hi
I am rebuilding the top end of a 550K1, the engine bore is standard and good, the pistons are good size wise. However somebody has been in the engine before me and cleaned the piston tops either with a belt sander or a wire brush on a grinder so there are marks all across the tops. They are not too deep and I could polish them out, but would lose a tiny amount of height and therefore compression. Just wondering what options are on that. I am going to hone the bores and put new rings on the pistons or put in new pistons and rings if needed.
Can the later F pistons with the raised crowns to increase compression 9.1:1 be used in the K1 engine. I am putting in a slightly hotter cam. Cam was knackered so have had to have it repaired and reground with a better profile. Thanks for any opinions or help.
Nurse Julie:
550F and 550K use exactly the same pistons and rings. It's the 750/4 that are different, the F model had the domed pistons, the K's didn't.
Bryanj:
As Julie says all the 550 pistons are the same, somewhere i have a set of Yoshimura +0,5mm piston kits but they aint cheap and neither is the rebore
Murf:
Yoshimura pistons :)
Great pistons but unfortunately a bit overkill for what I am doing but thanks.
I checked all the ring end gaps today and they are all in the region of 0.025 thou so out of spec but still within the max tolerance which I believe is 0.027’’ The top of one piston has quite bad damage so am thinking of getting new standard pistons and rings so thinking of trying the IMD ones. The thing I am worried about with the later F pistons is if the valves on the K engine are likely to hit the domed piston, I will have a check to see if there is any info about this.
Hi Julie I do need a couple of parts you have on your eBay site, cam chain, oil pump O rings and carb seals. How do I get the 10% off thanks.
Bryanj:
There are no domed pistons in the 500 or 550 range, the ONLY domed pistons are 750
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