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My 750F2 project.
K2-K6:
For us on here ordinarily accustomed to std Honda pistons and their metallurgy https://www.jepistons.com/je-auto-blog/2618-vs-4032-piston-material-differences/ gives good appreciation of that supplier and the alloy specified as used here.
You can see, just within their own range of alloy, that 2618 expands at + 15% over the alternative, let alone the stuff we are referencing and of cast higher silicone content Honda OEM parts....these effectively expanding more or less a match with the cylinder construction.
They'll get to the same clearance once warmed up though.
Cb750r:
Not much to show for at the moment, but I have my spare set of cylinders (2 cracked fins on one corner) sent out to the machinist recommended by many after sharing my experience. I have also taken the delay as an opportunity to send my crank down to APE race parts in California for lightening balancing and polish of journals.
I have a balanced alternator also on the way. APE will be sending their clutch kit back with the crank which “should†bring an end to the list of purchases for the engine internals.
I have a set of ZX14 forks and triple clamps. I had previously purchased for another bike (Zrx1100) I’ve been eyeing up for duty on the front of the CB… I’m in the process of turning a new stem on the lathe, will see how things progress. I’m not in a rush to make that swap but I’m in a bit of a holding pattern at the moment so spent some time on the lathe.
Laverda Dave:
--- Quote from: K2-K6 on February 14, 2024, 08:13:15 PM ---For us on here ordinarily accustomed to std Honda pistons and their metallurgy https://www.jepistons.com/je-auto-blog/2618-vs-4032-piston-material-differences/ gives good appreciation of that supplier and the alloy specified as used here.
You can see, just within their own range of alloy, that 2618 expands at + 15% over the alternative, let alone the stuff we are referencing and of cast higher silicone content Honda OEM parts....these effectively expanding more or less a match with the cylinder construction.
They'll get to the same clearance once warmed up though.
--- End quote ---
Thanks for posting this Nigel, that was an education for me. The pistons used by Morgo in their Triumph 750 conversion kits are forged. Unfortunately the person who originally built my engine decided to swap them out for Hepolite cast pistons but kept the compression really high. When I stripped the engine down after just 320 miles those cast pistons were oval!
McCabe-Thiele (Ted):
Very interesting link about Piston Materials Technology.
As a student back in the mid 1960's I bought a set of mint looking (used for one race) Hepolite Forged Racing Pistons for my first humble 850cc Mini at the bargain price of £25.00.
At the time I was a student living in Bradford so visited the Hepworth & Grandage Factory Trade Counter who supplied me with a complete set of new rings. They also sold me a special set of Champion Spark Plugs for the highly tuned engine. I came out of the shop substantially poorer.
Looking back putting a used piston in my 45k mile Mini is not something I would do today. They had cut away skirts with the oil control ring being just under the Gudgeon Pin if my old memory serves me right.
Cb750r:
Pressed in my new bronze Swingarm bushings last night. Also took measurements for future reference, (aka I own a lathe and should’ve made these)
Recovering from Covid, progress in the shop and life was slowed to a crawl for a bit there. Glad to make a little forward progress…
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