Im in the process of deciding what to buy - a 50cc or a 67cc (alleged 80cc) kit.
My situation is this...
I can buy both for nearly the same cost (in fact for me the 50cc kit cost $10 more! but big deal - that isn't a deciding factor.
Once I have the kit I will fit it with a tuned, tapered header, expansion chamber and a dellorto rep. 19mm carb.
Now the problem is, once I have a kit I would LIKE to balance the engine. The problem is that I dont have a spare conrod to weigh the big/little end and thus I would have to split the crank. Spliting the crank maybe hard because I don't have a press - just a vice and big hammer
However once apart I can assemble it easily as I have a lathe and the necessary measuring equipment. I could also guess the mass of it (weigh the little end than add the little end times 0.666 to get a rough final mass?)
Now my problem is, does anyone think It's possible to split the crank with a hammer without damaging the crank itself (ie use a piece of rod to drive out the crank pin with the crank mounted on a copper slab to protect it, etc)?
Now this only applies to the 67cc kit as the 50cc kit should come balanced - but me thinks that there is still room to improve on the 50cc engine balance? is this true?
One other thing is (not sure where Im going with this)... I will port my engine for all out torque (even experiment with tuned intakes) because with a single speed setup you need the torque.
To make sense of what Im trying to get at here, lets come up with the X factor - let this be the port width divided by the engines displacement...Then a engine with a bigger X factor for a given displacement (so a wider port) will have more torque...As the wider the exhaust port = more torque.
Now, for a fact the 50cc and the 67cc engines both use the same exhaust pipe, thus same exhaust bolt pattern thus same exhaust port size! Now that means that the 50cc engine will have a bigger "X" factor than the 66cc engine - however the 66cc engine will create more torque as it burns more fuel... this is where Im stuck. I dont know what engine will have more torque - are they the same? or one has more torque than the other?
Hang on i got an idea... if you calculate the 2 X factors (one for the 50cc and one for the 66cc) it turns out that the 50cc X factor divided by the 66cc X Factor equals 1.375.
Now, the only difference between the torque of the 50cc and the 66cc engine is the piston diameter. So If you take the piston diameter of the 66cc and divide it by the piston diameter of the 50cc it turns out to be 1.381.
So from this crude calculation I think that the 66cc engine will make more torque (as 1.381 > 1.375) - even with its "smaller ports to the engine size"?!
What are your thoughts guys?
Can you split a crank with a hammer with no damage if your careful?
Is the 50cc engine balance good or does it still need improvement?
Would the 50cc or the 66cc engine produce more torque given that they both have the same exhaust, carb and both are balanced... even though the 50cc has bigger ports to its displacment than the 66cc?
My situation is this...
I can buy both for nearly the same cost (in fact for me the 50cc kit cost $10 more! but big deal - that isn't a deciding factor.
Once I have the kit I will fit it with a tuned, tapered header, expansion chamber and a dellorto rep. 19mm carb.
Now the problem is, once I have a kit I would LIKE to balance the engine. The problem is that I dont have a spare conrod to weigh the big/little end and thus I would have to split the crank. Spliting the crank maybe hard because I don't have a press - just a vice and big hammer
However once apart I can assemble it easily as I have a lathe and the necessary measuring equipment. I could also guess the mass of it (weigh the little end than add the little end times 0.666 to get a rough final mass?)Now my problem is, does anyone think It's possible to split the crank with a hammer without damaging the crank itself (ie use a piece of rod to drive out the crank pin with the crank mounted on a copper slab to protect it, etc)?
Now this only applies to the 67cc kit as the 50cc kit should come balanced - but me thinks that there is still room to improve on the 50cc engine balance? is this true?
One other thing is (not sure where Im going with this)... I will port my engine for all out torque (even experiment with tuned intakes) because with a single speed setup you need the torque.
To make sense of what Im trying to get at here, lets come up with the X factor - let this be the port width divided by the engines displacement...Then a engine with a bigger X factor for a given displacement (so a wider port) will have more torque...As the wider the exhaust port = more torque.
Now, for a fact the 50cc and the 67cc engines both use the same exhaust pipe, thus same exhaust bolt pattern thus same exhaust port size! Now that means that the 50cc engine will have a bigger "X" factor than the 66cc engine - however the 66cc engine will create more torque as it burns more fuel... this is where Im stuck. I dont know what engine will have more torque - are they the same? or one has more torque than the other?
Hang on i got an idea... if you calculate the 2 X factors (one for the 50cc and one for the 66cc) it turns out that the 50cc X factor divided by the 66cc X Factor equals 1.375.
Now, the only difference between the torque of the 50cc and the 66cc engine is the piston diameter. So If you take the piston diameter of the 66cc and divide it by the piston diameter of the 50cc it turns out to be 1.381.
So from this crude calculation I think that the 66cc engine will make more torque (as 1.381 > 1.375) - even with its "smaller ports to the engine size"?!
What are your thoughts guys?
Can you split a crank with a hammer with no damage if your careful?
Is the 50cc engine balance good or does it still need improvement?
Would the 50cc or the 66cc engine produce more torque given that they both have the same exhaust, carb and both are balanced... even though the 50cc has bigger ports to its displacment than the 66cc?
