Less reciprocating mass - pros and cons ?

[Dogger]

I recently found out new product for my bike: a titanium piston pin. It weighs half of the stock steel pin, so the reciprocating weight would be reduced by 41grams. That represent 7% of total (piston, rings, pin, small end bearing) in my bike (CR500).
There are certain benefits (at least in theory) for using it, I think: less stalling, freer revving engine (more overrev?), less stress on bearings, maby less vibration... but I would like to read Your opinions if there are any bad effects using lighter component like this? I know nothing about crank balancing but I think it will change also. How would it change? Will it vibrate more on lower or higher revs? Should the crank be lightened to get better balance?

 

[mxneagle]

I doubt that it would impact crank balancing since it is not a rotary mass item.

 

[Studboy]

I could be wrong here, but I think that any lightening that you do to the reciprocating mass (piston/rod/etc.) in your engine without affecting strength, is good.

 

[slodsm]

The thing hardest on the rod bearing and rod of any engine 2 or 4 stroke is the moment of stopping at the top of the stroke when the piston is practically trying to be flung out of the engine and then stopped and pulled back down. Any weight you take off the top will be beneficial. (sp)

 

[pace]

slodsm is correct. The tensile forces he refers to increase exponentially with RPMs, and are a function of piston mass. Reducing the weight of your topend components is certainly a good thing from that perspective, if you can do so without compromising durability. I think you may need to research more on whether balancing will be necessary, however. I know when I purchased a big bore kit for my CBR1100, the pistons had been machined to keep them as close to the stock weight as possible. I was told this was to obviate the need to balance the crank.

-Pace