Piston weight - comparison OEM cast vs. BB forged:

[sam2019]

There have been remarks on other forums by the usual "experts" that a BB piston would put stress on the crank because the bigger piston would be heavier.
Not so, The cast OEM is lighter than the bigger forged BB piston. But not by much. That is because other lighter materials are used in making it.

Pictures are a 350 cast vs a 441 forged (didnt have any 411 vs 477 available for the comparison but the weight relation should be similar)
No pin in the forged - which is 80g.

 

[sam2019]

Pin is 61g actually

 

[sam2019]

Apart from this there is the statistical data speaking for a solid crank function despite slightly higher piston weight:

Over 50.000km in a 2016 Hima model that first ran as 477, then as a 500.
More than 100 BB sets and zero crank fails in any of them afawk (and that would be reported to us 100%!)
Over 100.000km in various Himas now, even those run as rentals, speak for a VERY solid engine design.
I have only ever heard of or seen 3 crank failures, all in 411 versions and all due to lack of oil.

 

[Dool]

Having seen the Crank Bearings I believe that 100%
They are over engineered, the engine is badly designed for power but well designed to last a lifetime.
Lack of oil will kill any engine no matter how well it is made or designed.
My 500 and even my 511 showed no signs of being out of balance and those pistons weighed a lot more than OEM.
The New 452 vibrates more than any of my builds ever did.
Whether a J series can be fitted with a 86mm Forged piston which weighs 370grams complete is another thing.
I will give it a go!

 

[sam2019]

Whether a J series can be fitted with a 86mm Forged piston which weighs 370grams complete is another thing.

I am sure it can, but I am also pretty certain that liner will not fit without modifying the opening of the body. But who knows, miracles do happen. I assume you will use a 535 conti piston?

 

[sam2019]

This is the 410cc OEM piston with pin and rings - 50g more than the 350 OEM

 

[Dool]

I am sure it can, but I am also pretty certain that liner will not fit without modifying the opening of the body. But who knows, miracles do happen. I assume you will use a 535 conti piston?

Conti piston would involve raising the barrel as its taller than the others.
I would just be using the 500 piston from the Himalayan line of big bores.
I have plenty of options even 443cc(81mm) that should make a big enough difference ie 113cc increase in displacement.
Boring bit is completing the running proceedure first.

 

[sam2019]

Finally I got a new batch of 84mm forged and here is the weight: with pin and rings