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When I bought a bunch of old Shindaiwa parts a year ago mixed in the pile was an odd cylinder. It looks just like the 5-6 series (45, 49mm) but is a 51mm like the 7 series (750, 757), and is a closed port, unlike the 5/6 series. 7series are closed but completely different cylinder design.
It does not fit the 757 case but does fit the 575/680/695 case. Soooo.
I put a case together today and played with the 49 vs 51mm topends. The 757 51mm piston is a bit taller (2.5mm) than the 695s 49mm but that was easy to fix by slightly beveling the bottom corners of the 51mm piston skirt. Piston crowns are exactly the same. Squish for the 51mm, no gasket, is around .030.
Squish for the stock 695 topend....060+ . I know these are domed pistons but, sheesh.
The 51mm piston I'm using is trashed...just needed one for testing...I have nos.![1000004947.jpg 1000004947.jpg](https://opeforum.com/data/attachments/427/427528-f8ccde6f0527544bca3ccdcf546afc02.jpg?hash=-MzebwUnVE)
If it works out I'll have a 695/757 hybrid...well, sort of,![Stick Out Tongue :p :p](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f61b.png)
![1000004945.jpg 1000004945.jpg](https://opeforum.com/data/attachments/427/427521-8800a1cb3b5c2d77eb3f329832a786d0.jpg?hash=iAChyztcLX)
![1000004939.jpg 1000004939.jpg](https://opeforum.com/data/attachments/427/427522-ec5a332f317b0e099dfef46336f8ec36.jpg?hash=7FozLzF7Dg)
![1000004949.jpg 1000004949.jpg](https://opeforum.com/data/attachments/427/427524-434498d8936eae92b0f0e02f1d3dfd16.jpg?hash=Q0SY2JNurp)
It does not fit the 757 case but does fit the 575/680/695 case. Soooo.
I put a case together today and played with the 49 vs 51mm topends. The 757 51mm piston is a bit taller (2.5mm) than the 695s 49mm but that was easy to fix by slightly beveling the bottom corners of the 51mm piston skirt. Piston crowns are exactly the same. Squish for the 51mm, no gasket, is around .030.
Squish for the stock 695 topend....060+ . I know these are domed pistons but, sheesh.
The 51mm piston I'm using is trashed...just needed one for testing...I have nos.
![1000004947.jpg 1000004947.jpg](https://opeforum.com/data/attachments/427/427528-f8ccde6f0527544bca3ccdcf546afc02.jpg?hash=-MzebwUnVE)
If it works out I'll have a 695/757 hybrid...well, sort of,
![Stick Out Tongue :p :p](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f61b.png)
![1000004945.jpg 1000004945.jpg](https://opeforum.com/data/attachments/427/427521-8800a1cb3b5c2d77eb3f329832a786d0.jpg?hash=iAChyztcLX)
![1000004939.jpg 1000004939.jpg](https://opeforum.com/data/attachments/427/427522-ec5a332f317b0e099dfef46336f8ec36.jpg?hash=7FozLzF7Dg)
![1000004949.jpg 1000004949.jpg](https://opeforum.com/data/attachments/427/427524-434498d8936eae92b0f0e02f1d3dfd16.jpg?hash=Q0SY2JNurp)