2 stroke pistons

[Flywheel]

hi

does the shape and size of the ports in a 2 stroke with reed valve effect the performance cause i recently put a new piston im my honda ns125r but when i got it the ports where different sizes and shapes.I phoned up the company the piston came from, Stan Stephens, and they said it dosnt matter cause its got reed valves.

So after fitting the piston and running it in i found the performance of the bike had droped.It had a slower top speed and slower acceleration.

OH ye the piston that came out was the original honda one cause i looked in the manual at the pics.

[kev]

In a word yes they will affect it.

Take it apart and send the bits back and tell them to send you the right bits.
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20:02:36 Jammy-R6: any holes a goal
20:02:48 kev: even if its a hairy mans arse
20:02:56 Jammy-R6: hell yes

[Skvara]

But if it is new piston you should get it rode. You can't go as a racer with new piston!!!

[kev]

[aRe_eSs]

bed it in is what i think was meant?
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>> Nova boy in rehab.....

[Guest]

As I understand it, reed valves simply close on the compression stroke stopping the mixture being forced back through the carb. The ports in the barrel must match the cut-aways in the piston otherwise they're not working as they should. It would restrict the power as you've found, like blocking off part of the exhaust or inlet (which is what's actually happening)

[Flywheel]

Thanks for the help.Im gona get the right piston now.I would have also thought that Stan Stevens would know what they where talking about since they are 2 stroke tunners.

oh ye this is after i ran it in.

[cagiva gezzer]

Some people sell pattern pistons that do almost the same job as OE pistons, but because they are manurfactured differently they are of different density and therefore can not be made to the same shape.

No doubt the piston was a weisco or prox one. From my experince with pattern mito pistons, the prox ones have lower side skirts and smaller windows which do not work as well as the OE ones.

Even though the ensine is a reed valve engine, the timing is also controlled be the height of the piston and the shape of the windows.

I've got nothing against stanstephens or the "other main prox dealer", as they have served me well in the past, but stick to OE pistons.
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"because one stroke isnt enough and four strokes waste two"

[Skvara]

kev:sorry I cannot translate it to better English but if you want I can post it here for you in Czech

[kev]

Sorry mate I just thought you were a chav doing text talk kind of thing.
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20:02:36 Jammy-R6: any holes a goal
20:02:48 kev: even if its a hairy mans arse
20:02:56 Jammy-R6: hell yes