Does anyone know for sure if the 100cc and 125cc cylinder are the same casting? Meaning, does IAME use the same cast iron sleeves for both cylinders? The only difference being the final bore sizing, 100cc = 48.2mm & 125cc = 54.0mm. If IAME uses just one linear, the wall is 2.9mm per side thicker on the 100cc vs 125cc.
Bottom line, can a 100cc cylinder be bored to 54mm to reach 125cc displacement. The bottom ends are the same between the two engines. I also now the heads are different. I’m looking at buying a 100cc engine for parts. I have a 125cc
Different castings, port dimensions are completely different. And boring 6mm from the sleeve would change the heat transfer characteristics of the cylinder a lot.
If its just for a fun experiment you could give it a go. Generally when 100s are bored out it’s to 116cc because they are (mostly) 50x50 but in this case it looks like it has a longer stroke.
If it’s cheap to do, it’ll be fine for practice. I think my main concern would be the balance factor on the crank for the heavier piston. Also, you’ll need the head machined to maintain the correct head volume. 9.8cc head on a 125 is kill mode
Just a couple things James. The bottom ends of the 100cc and 125cc pre MY09 Leopards are the same, same crank and rod. Same crankcase and cylinder studs and bolt pattern. The Cylinder heads are different between the two displacements, the 100cc head uses a smaller diameter inner head gasket O-Ring.
No worries on the crank balance, all bottom end part numbers are the same between the two engines.
Also, WKA calls out 9.5cc spec on combustion chamber volume for Leopard and X30 125’s.
I might be thinking 6.5cc from 100 then… But you’ll have to swap the head anyway from the looks of things so what I said is moot.
If the P/N is the same for the crank then I think you can say it’s good enough right there.
Thanks Christian, I was wondering about port timing and shape if they did use/start with a thicker castiron sleeve on the 100cc. Lets say for thermodynamics IAME uses the same iron wall thickness and the same aluminum wall thickness between the two displacement. That would means the water jacket cooling area would need to be LARGER on the 100cc cylinder. That also would effect heat transfer, more potential heat transfer on the 100cc cylinder. The 100cc wouldn’t need it.
I’d really like to see a 100cc cylinder myself…
Anybody have photos of a 100cc cylinder for comparison?
Actually one thing to check is pin to crown distance on the two pistons. You might be able to find a 100cc homologation sheet out there.
I wouldn’t worry too much about the thickness of the liner in terms of heat transfer personally.
But the port area and port transfer angles will change with the overbore.
Okay, my goal and thought here is to buy a used 100cc Leopard on the cheap. Use the bottom end for spare parts if needed, again bottom ends and rods are the same between the two displacements. The main purpose is (if possible) bore and hone the cylinder with a fitted piston at the ready as a spare replacement when needed for my current 125cc. I can buy a used 100cc leopard engine for less then the cost of a new 125cc cylinder.
We have snow on the ground here in Wisconsin, I’m bored and my mind is wandering…lol
I found engine tech spec on port dimension between the two engines. As you said, totally different port configurations. Delete idea from brain.100cc_jr_leopard_specs.pdf (633.2 KB) leopard_rules_2005_4 125cc.pdf (1.3 MB)