Sport port templates

I've never used the sport port templates, but I've used the Yamanube template on a 760. The stock port timing on a 760 is a little higher than the yamanube template so I just slid it up slightly to match the top of the oem port and marked it out and ground away.
 
The Race Logic templates typically open the width to about 75% of the bore and that's why my rings snagged and tore off the piston crown. If they were a bit more modest and maxed out at about 65-68% there probably wouldn't have been a problem.
 
Yup, but too wide of a port allows the rings to oblong too much and squeeze into the port too far. That's what happened with mine. I ran the motor for a good while before it happened. It must have been a heat thing expanding the rings a little more than usual, getting more skilled at riding, putting more demand on the motor. Since I went to the Yamanube templates I haven't had any issues and that has been a good few years now :)
 

yamanube

This Is The Way
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Mandalor
The shape of the sport port template felt a little aggressive to me as well (for a reliable rec ski), that is why my template is slightly less wide and has a larger radius on the top corners. One thing I found out while messing around in CAD drawing my template was that the way the template lays into the cylinder, as the bore increases, the width of the port template increases and the result is that the width ratio stays relatively the same.
 
The shape of the sport port template felt a little aggressive to me as well (for a reliable rec ski), that is why my template is slightly less wide and has a larger radius on the top corners. One thing I found out while messing around in CAD drawing my template was that the way the template lays into the cylinder, as the bore increases, the width of the port template increases and the result is that the width ratio stays relatively the same.
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