[quote author=363C3A323E316B6E666C5F0 link=1554362214/30#44 date=1557538261]
DragBikeMike wrote on 05/06/19 at 23:30:36:I ah see it now. I am trying to decide between a 95 or a 96mm wiseco piston right now and I am assuming opening up the exhaust a bit to allow for better flow for larger displacement would be good. Any ideas on the 95 vs the 96?
When I built my engine I chose the 95mm, as it was the smallest Wiseco piston available at the time (Lancer had not had the custom Wiseco in the stock 94mm size being built yet).
The reason I used the smallest piston - is that I seldom need to use "all" the HP that my engine can make, and the majority of my riding is done on twisty county roads between 40-60 mph....and this requires 1/4 - 1/2 throttle. I wanted an engine that was economical, reliable and ran well - I was not after maximum HP. I also wanted to be able to bore the cylinder again if needed - however I now realize that the Savage engine really doesn't have any piston/cylinder issues as long as you keep the oil level up and use a good oil - Youzguyz got 160,000 miles on his bike and was able to re-use the piston and cylinder when he had his engine overhauled.
I think the cylinder head is the big restriction in how much power the engine can produce - and on a dyno the piston size is likely to make a difference on "where" the power is produce - more than on how much power is produced. I believe there is a possibility the larger pistons will reach the airflow limits of the head at a lower rpm than the smaller pistons will. So....I would expect the 94mm piston will have the maximum torque at a bit higher rpm than the 97mm piston will. The bigger pistons will make a bit more torque than the smaller pistons....but they will likely start to run out of air a bit sooner than the smaller pistons will.
So - I believe that if you want maximum bottom end grunt, you should go with the bigger piston.....even as big as the 97mm. If you want a good running engine that makes more HP because of the higher compression ratio.......but do not use full throttle often.....go with a 94mm piston and save the cost of the cylinder boring if your cylinder is in good shape.
I am well satisfied with how my 95mm Wiseco engine runs.....it is a joy to ride. Maybe someday I will build a 97mm engine and see if I am missing anything.
So