Jug for what engine stroke length?

[mapbike]

Im sure thia question needed to be ask in another topic section on here, but I thought it may get quicker attention here in the general section.

(Mods, Feel free to move if this past needs to be moved)

As some of you know Ive been out of the game a while now so there are some newer parts and newer engine designs that have come out over the last 3 or so years amd Im not familiar with them other than simply seeing them.

Question:.....

I recently purchased a new jug with open transfers, the center post in the exhaust port opening amd it has really smooth casting compared to what Ive always got in the years past.

Are these jugs designed to have beat plet timing with A type low hole or B type high hole piston?

Thank you in advance for the help on this.

 

[Larry Trotter]

The connecting rod length determines the piston type not the cylinder.

 

[mapbike]

I know that fact, been working on these little engines since 2009 sir.

depending on the geometry of the engine some jugs/cylinders offer better port timing

Example: a GT5 engines stock cylinder will have different port timing if its put on a PK80/ low pin piston engine.

Then there is also the "half breed" engine which has an even differnt crank stroke but also uses the low pin piston, its sort of a cross between the PK80 & GT5 kind a little of both all rolled into one with the lower rod journal placed differently on crank than the others.

So all of this is why I ask the question, just curious about which engine geometry these G4 jugs were originally intended for if anyone here knew and didn't mind telling me.

The connecting rod length determines the piston type not the cylinder.

 

[Larry Trotter]

I don’t believe a high or low pin piston is necessary related to the stroke length either long or short. The cylinder port position would be different depending on stroke but the pin position on the piston is dependent on the rod length not the stroke length or the cylinder port location.

 

[mapbike]

excluding the " half breed" geometry engines

yes the piston pin can be an indicator of the engine stroke length.

PK80 low pin piston

GT5 high pin piston

These two engine have a different stroke length and I have several jugs originally designed for eacu geometry and the jug off tje PK80 engine has differnt port timing when put over on the GT5 engine and vise versa.

that is why I was curious if anyone knew which geometry the G4 jugs was originally designed for.

no biggy... when I get ready to build the engine Ill figure it out real quick when I place jug on lower with piston installed.

I don’t believe a high or low pin piston is necessary related to the stroke length either long or short. The cylinder port position would be different depending on stroke but the pin position on the piston is dependent on the rod length not the stroke length or the cylinder port location.