| Powered by phpBay Pro |
what can I expect from changing to a high compression piston from a low compression piston? any disadvantages?
I've already port & polish, reboar, racing (cams & cdi) harder valve springs...my motorcyle is a short stroke 125cc
since you mentioned the race cam you will most likely need a new piston. First off, just about every high lift / long duration aftermarket cam shaft will require a piston with valve clearance recesses in the piston crown. A "race" cam will also have more intake/exhaust timing overlap which kills low end performance and will not idle easily or smoothly due to the blow back through the carb at low RPM. many times you have to get a high compression piston to make up for the low compression at low RPM due that that overlap. Many times the valve pockets negate the decrease in combustion chamber capacity.
What can you expect from changing to a high compression piston? Possibly less vibration if the new piston is lighter than the stock component. More vibration if the piston is heavier. More engine heat - though the higher heat has the affect of more efficiently creating greater energy from the intake charge there are some downsides to heat: you need to change your oil more often, engine should only be ran at high vehicle speeds for best cooling, you don't want to stand around idling, peak power is obtained over less time due to the incoming air being preheated and fuel vaporizing in the carb making it harder to siphon into the incoming air stream, increased detonation, and shorter valve - valve seat and spark plug life.
High compression is best achieved with a flat top piston and reducing the size of the combustion chamber in the head either by welding or machining the mating surface. Milling the head is not always a straight forward practice with overhead cam engines.
High compression has the trade-off of more power everywhere with decreased engine life. You figure out which is more important to you.
Items Recently Purchased From This Site:
| Powered by phpBay Pro |
