72cc vs 80cc

[magoconnor]

Hello.

Right now my 139qmb engine is installed with a 72cc cylinder, but I'm thinking about upgrading to a 80cc. 

Has anyone done the same move? And if so, is the step up worth it?  (Overall Perfomance)

If I go with a 80cc cylinder, I plan to run it with a 47mm bvh. Will this be okay? or will the compression be too high? 

[fugaziiv]

It's really not recommended to run the 50mm or larger kits with smaller or stock heads. The compression can be really high and it sometimes causes the pistons to break apart. This is why we list on our site that the performance head is very highly recommended, we've seen too many failures on even high end kits to consider otherwise.


Matt

[greginisn]

It seems the general consensus is the 72cc BBK is your best bet regarding engine longevity compared to a stock setup so consider that, or maybe buy a 150?

Greg