I can't speak to your questions about the pump. I don't have a production engine. My have been prototype engines. I do have one of the "production pumps" running on a 170 and it is running the same as the 160 pump I had on that engine.

The hole in the rear disc of the crank was my understanding to improve lubrication of the front of the engine. You will also see Small hole in the crank near the cam gear area this allows for better flow of oil to the cam. The connecting rod has some changes in it also at both ends to better lubricate the connections and the crank pin shape is a changes a little to accommodate this better lubrication change on the rod.

As far as I know the only change to the pump was the housing...and the bore, and shape of the piston inside the pump. I have not compared springs and plunger parts from the pumps but I can at some point. I want to get a production engine and compare it side by side with the 160DZ production engine. I only have 1 production 160. The other 2 are test engines that have been updated with some production parts. My 170's all 3 of them I have had are slightly different from each other. The only changes I have not run are the new case. This is because I have basically not needed a new case. The newer style crank, pump and the other 170 changes including various throttle barrel seal changes have been tested on my engines. I don't know if Yamada used the changes to the throttle barrel or not. I have had 3 different engines with 3 different throttle barrel versions. One of them was a 160 carb and barrel because I pulled it off one of my 160's. To my understanding the carb and throttle barrel are basically no changes functionally, just the o-ring was replaced with the oil seal from the 140L. I don't know if this is what is happening on the production engines or not.



Troy Newman
Team YS