Author Topic: Should i go A or B size for 1st piston?  (Read 238 times)

Runner

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Should i go A or B size for 1st piston?
« on: November 08, 2020, 10:21:53 AM »
Hi all.
I'm about to do top end rebuild on my 2018 SE250, trying to decide if to go A or B size piston, I could not find the letter stamped on the cylinder.
Anyway, itís the 1st piston for this bike and my mechanic told me to go with B straight as it could even be a little better.
I know the size difference between A and B is minor but, why than there would be 2? Anyone has experience or can explain why would I use B or will there be any difference compared to A?
Thanks.


Trailrider383

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Re: Should i go A or B size for 1st piston?
« Reply #1 on: November 08, 2020, 12:40:56 PM »
You have to match the piston to the bore for the proper clearance. Which means precision measurement of both.

erdat

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Re: Should i go A or B size for 1st piston?
« Reply #2 on: November 09, 2020, 01:10:58 AM »
Trailrider383 iş correct. But many "mechanics" I had experience with do just put the next bigger piston.
Also Sherco provides only two size oem pistons, and if I am not wrong prox has 4 sizes available. Tokyo offroad in YouTube has a very good video on showing how to take cylinder bore dimenson measurements,
-erdat
« Last Edit: November 11, 2020, 05:28:33 AM by erdat »
'15 SE-R 250
Ankara, Turkey

Trailrider383

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Re: Should i go A or B size for 1st piston?
« Reply #3 on: November 09, 2020, 05:49:12 PM »
I ride trails, not trailers.

Trailerrider383 iş correct. But many "mechanics" I had experience with do just put the next bigger piston.
Also Sherco provides only two size oem pistons, and if I am not wrong prox has 4 sizes available. Tokyo offroad in YouTube has a very good video on showing how to take cylinder bore dimenson measurements,
-erdat

Gartzza

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Re: Should i go A or B size for 1st piston?
« Reply #4 on: November 11, 2020, 01:05:55 AM »
After 150 hours of riding I stayed with the same A piston, when changed it for the first time. Didn't measure anything, so maybe this is not correct way, but bike feels good.

erdat

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Re: Should i go A or B size for 1st piston?
« Reply #5 on: November 11, 2020, 05:30:14 AM »
Dear Trailrider383, my sincere apologies. I've corrected my error in the pervious post.

I ride trails, not trailers.

Trailerrider383 iş correct. But many "mechanics" I had experience with do just put the next bigger piston.
Also Sherco provides only two size oem pistons, and if I am not wrong prox has 4 sizes available. Tokyo offroad in YouTube has a very good video on showing how to take cylinder bore dimenson measurements,
-erdat
'15 SE-R 250
Ankara, Turkey