Does it have the wide front mount?Took a close look at my generic "Pizhou Yongxing Gasoline Engine Factory" 80cc today. Although it has the slant head the piston does not rise above the jug at TDC. Also the piston has a flat top with the number "two" stamped but no arrow. It would seem there are destinctions between the PK-80 (also "Pizhou Yongxing Gasoline Engine Factory" ) and my less expensive generic. I just thought I would add to the data base.
Below: the bottom of my head after dremel and polish work. Also a couple pics of the motor straight from the box.
Thank you. Now I am curious if my Zoom slants have the dome piston and what determines which one you get. I wonder if you can tell by looking in the plug hole.Yes, wide front mount.
nothing generic about that phizou yongzing its a power king awesome motor. yes the slant head adds power all around i did a run with the straight head and followed by the slant and it was way more powerful..Took a close look at my generic "Pizhou Yongxing Gasoline Engine Factory" 80cc today. Although it has the slant head the piston does not rise above the jug at TDC. Also the piston has a flat top with the number "two" stamped but no arrow. It would seem there are destinctions between the PK-80 (also "Pizhou Yongxing Gasoline Engine Factory" ) and my less expensive generic. I just thought I would add to the data base.
Below: the bottom of my head after dremel and polish work. Also a couple pics of the motor straight from the box.
GREAT INFO IM GOING TO BUY 1 OF THOSE PK 80 NEXT THANK YOU FOR POSTING THIS KIND OF MATERIAL !!!!!No the PK80-J is allmost 69CC total. like 68.8 something. "stroke X bore dia."
But to find compression. "Corrected Compression"
We use the swept volume of the piston above the exhaust port.
Compression dosent start until the exhaust port is closed so we use the volume of the cylinder above the top of the exhaust port.
So thoose numbers at like 15 :1 or 16:1 compression are UNcorrected.
They take the complete volume of the cylinder and use for calculation but with the ports open there isn't much compression yet.
Other than the PSI in the CrankCase and PSI caused by Expansion Chamber slammin fuel back in the chamber.
Which will add some PSI to the actual calculated compression.
But lets see.
69cc / 5cc = 13.8 :1 Uncorrected Compression Ratio.
So be careful when you talk compression and make sure you know if were talking Corrected or UNcorrected compression.
It makes a big difference in the numbers.
Going much higher than 9:1 Corrected Compression probably won't help much.
at a certin point you actually have a detrimental effect.
Make sure you cange that caged needle bearing if you go high comp.
It puts much more strain on things.