Not too fast but very furious

pyoungbl · 08-12-2021, 02:21 PM

Going for a big big bore, with its heavier piston, should not be a big problem if the crankshaft is also balanced for the new weight. In fact, the new setup might even be smoother than when it came out of the factory. That's exactly what I found when I did a BBK on a Ducati Multistrada. Once the crankshaft was correctly balanced the engine was much smoother running even though it had higher compression and more displacement.

The inexpensive big bore kits being installed only include piston and cylinder. The pressed crankshaft remains balanced for the stock piston. Lowering the redline sounds like a must to me. If one were to balance the crankshaft it would require splitting the cases, then sending the crank, rod, and piston out to a specialist. I'm guessing $500 worth of labor in total. That takes a $200 mod up to $700 in order to gain a few hp...probably less than 3-4 hp. Once done the bottleneck is intake and exhaust. This quickly becomes a point of rapidly diminishing return in terms of power for money spent. BTDT.

08-12-2021, 02:21 PM	#10
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	Going for a big big bore, with its heavier piston, should not be a big problem if the crankshaft is also balanced for the new weight. In fact, the new setup might even be smoother than when it came out of the factory. That's exactly what I found when I did a BBK on a Ducati Multistrada. Once the crankshaft was correctly balanced the engine was much smoother running even though it had higher compression and more displacement. The inexpensive big bore kits being installed only include piston and cylinder. The pressed crankshaft remains balanced for the stock piston. Lowering the redline sounds like a must to me. If one were to balance the crankshaft it would require splitting the cases, then sending the crank, rod, and piston out to a specialist. I'm guessing $500 worth of labor in total. That takes a $200 mod up to $700 in order to gain a few hp...probably less than 3-4 hp. Once done the bottleneck is intake and exhaust. This quickly becomes a point of rapidly diminishing return in terms of power for money spent. BTDT.
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