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Author Topic: oversize piston?  (Read 545 times)

chaz35

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oversize piston?
« on: January 18, 2015, 02:58:24 PM »
Has anyone bored out the OEM cylinder for more displacement?  As I understand it, the BBKs have modified ports for more performance, probably raised and enlarged.  The oversized pistons are available separately, so just wondering?  If just riding on street, maybe would be good cheap way to get a little more performance IDK.  I expect some to say it won't work, but maybe someone has actually tried it that wants to comment.  Cheers
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BettinANDlosing

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Re: oversize piston?
« Reply #1 on: January 18, 2015, 04:30:21 PM »
Unless you have friends at the machine shop it'll cost about the same as a 70 cc kit without half the power gain. Anything is possible tho...
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zombie

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Re: oversize piston?
« Reply #2 on: January 18, 2015, 07:15:19 PM »
agreed. BUT I see your point. Keeping the OEM porting, and increasing the cc is a good idea.

I see two issues... Opening the jug will actually lower the ports because of the angles involved so you will have to re-port to get back what you lost.
Issue two comes back to B&L's post... Is it worth the time/money to do, and what if there is a slip up in re- mapping the ports. The jug is now trash.

I've bored lots of jugs for my ZX, and used many different pistons in these jugs. Some were Yamaha 80cc pistons in bored Malossi jugs, and Wiesco pistons on JiangWayne jugs, ect... The bottom line is they were all fun, and rewarding but a simple sport kit ie: Malossi or shaving down your OEM head for more compression are easier, and require less risk/work/money.

If you want to do this for fun I would recommend a 47.5mm piston from the Polini Corsa kit, and getting a NEW S-9 jug.
Bore, and re-port accordingly, and 8-9HP is a very reasonable goal.
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