If you look at 55:00 in the video, you can see that the cores are actually easily breaking up on their own due to the heat, and pouring out of the casting by themselves.
This is ideal when the cores break up after the pour, and it shows that he did not mix an excessive amount of epoxy into his core sand.
I have heard of people adding things like flour to their cores, to make them break up easier.
I have never had to resort to using flour, and have not had problems removing cores.
A common mistake I see with sodium-silicate cores is for them to be over-gassed with CO2.
A 5 second gas is the maximum you want to use with a SS core; any more than this will ruin the core.
SS cores should never be put in a bag full of CO2; this will cause them to disintegrate.
The exact ratio of sodium silicate to sand should be used, and no more (I forget what the instructions say, but somewhere in the 3-5% range as I recall).
People use excessive amounts of SS binder because they are over-gassing their cores, and excessive binder makes the SS cores very difficult to remove.
With the correct amount of SS, cores will break down easily, especially if water is added.
The speedy twin has two long narrow passaged that cross the top of the engine, and one is U-shaped.
They used core cleanouts at strategic places (see red arrows).
And the "freeze plugs" on an auto engine have nothing to do with freezing water; they are holes in the casting used to support cores.
The correct term should be "core support holes".
.
This is ideal when the cores break up after the pour, and it shows that he did not mix an excessive amount of epoxy into his core sand.
I have heard of people adding things like flour to their cores, to make them break up easier.
I have never had to resort to using flour, and have not had problems removing cores.
A common mistake I see with sodium-silicate cores is for them to be over-gassed with CO2.
A 5 second gas is the maximum you want to use with a SS core; any more than this will ruin the core.
SS cores should never be put in a bag full of CO2; this will cause them to disintegrate.
The exact ratio of sodium silicate to sand should be used, and no more (I forget what the instructions say, but somewhere in the 3-5% range as I recall).
People use excessive amounts of SS binder because they are over-gassing their cores, and excessive binder makes the SS cores very difficult to remove.
With the correct amount of SS, cores will break down easily, especially if water is added.
The speedy twin has two long narrow passaged that cross the top of the engine, and one is U-shaped.
They used core cleanouts at strategic places (see red arrows).
And the "freeze plugs" on an auto engine have nothing to do with freezing water; they are holes in the casting used to support cores.
The correct term should be "core support holes".
.
? I can relate to that 
.
