[Kit Contents] ・52.4Φ Forged Piston x 1 (stock size) ・Piston pin x 1 ・Piston ring x 1set ・Piston Pin Clip x 2
*Gaskets and other items that need to be replaced when removing and installing are not included.Please purchase separately.
[Features] High compression forged pistons that can be used with stock cylinders. Power up without changing the displacement! If you want to go faster, but don't want to big bore... But you don't have to.
Points of Attention
* If there may be an instruction manual included, it will be written in Japanese.
Fits: YAMAHA BWS125(BWS) Type 2 BG1 Domestic, YAMAHA BWS125(BWS) BWS R 2JS Taiwan, YAMAHA BWS125(BWS) X 46P Taiwan, YAMAHA CYGNUS X Type 1 5TY Taiwan, YAMAHA CYGNUS X Type 1 5UA Domestic
Since TIGRA's Engine Parts are not quite so, we have dealt with additional work again.
Originally the compression ratio 11 : TIGRA with a high compression ratio of 1, but when you enter High Camshaft the punch is gone. Probably because Valve is open for a long period of time, the effective compression ratio may have dropped. So High Camshaft got Normal piston because it was called High compression piston and compared it with High compression piston of Standard Bore size for CYGNUS made by KOSO.
◆ KOSO's Piston's own evaluation I thought it was very good and very good compared with PGOOEM Product. Oist pool of Piston Pin boss hole, OIL hole to Piston skirt etc.. , PGON normal processing was not done in piston. Material is like high-strength Duralumin which can be machined crisply. I figured out later, Piston PinOffset reversed TIGRA.
● Check the bore diameter system Normally for Piston for Water-cooled Engine, Piston becomes higher temperature than Water-cooled Engine, so it is considered to be more clearance considering thermal expansion. However, it seems that there is not much difference between Large. Furthermore, because the diameter of Piston Top Land becomes Small, it is concerned that it will become a big eyelid.
● Check height direction When comparing with Piston Pin as starting point, KOSO Forged Piston is about 1 mm on the Piston Pin, so processing is necessary. TopLand is shaved 1 mm by Risk Base Gasket 1 mm Addition Since there is a problem of Timing Chain, I set Piston 0. Shave 5 mm and base Gasket 0. It was decided to make it 5 mm thick.
● Valve Recess position confirmation INT is nearly together EXT because TIGRA is closer to the center, so additional work is required However, if PistonTop is set to 0. Because it cuts 5 mm, processing on the INT side is also necessary
● Compression ratio examination The compression ratio is 12 : I assumed about 1, but there was concern that it will become somewhat expensive even after applying the above processing. I decided to process a round indentation in the middle of Piston where the plug is located, referring to the Piston shape information that avoids Knocking that matches the Technical Report of MazdaDemiio's high compression engine.
Other than that there was no problem such as Piston Pin diameter. Since the direction of processing was decided, a jig for additional processing was prepared and processed with a lathe and a milling machine.
After processing, clay was affixed to Piston, temporarily assembled, confirmed the interference condition of Valve and made a book. The compression pressure is 13. 5kg / Cm 2
As we scooped out the Engine, we port polished ports and Intake manifold with Flap wheel to polish the surface with Tripoli and Felt buff.
After the break-in run and trial run, I returned to a healthy feeling before High Camshaft was launched. I think that it is equivalent to Fine tuning rather than improvement of horsepower. When looking at the air-fuel ratio meter somehow the air-fuel ratio is 0. It feels like it got about 5 thinner.
Piston slap sound is slightly bothersome but not too bad. It is suppressed around 9000 rpm in Weight roller setting, but it may be good to rotate a little bit. I'm thinking of putting Reinforced Valve Spring for KOSO's CYGNUS.
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