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Bantam d14 performance piston
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Joe6336
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April 6, 2021
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April 6, 2021 - 1:12 pm
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Good afternoon all just looking for a little advice regarding my recently acquired bantam. I bought the bike needing some work. The engine has been fully rebuilt but the gearbox reassembled incorrectly. I plan on stripping the engine to fix the gearbox fault but while I’m at it wondered about fitting a performance piston and having the cylinder rebored. Iv spoken to Rex caunt regarding upgraded pistons and they recommend I post here. I’m wanting the bike to be reliable but something that can keep up with modern traffic. I will be replacing the carb and fitting electronic ignition and 12v to try and update the bike and keep it reliable for sunny Sunday rides out. Thanks 

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AdrianS
Harlaston Staffs
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April 17, 2021 - 9:36 am
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2 questions:

1. Does the barrel need a rebore? Get it measured and check it needs boring.

2. what do you expect with a performance piston?

The D14 is already in a relatively high star of tune for a Bantam and unless racing it I would not recommend trying to improve on the standard state or you may end up with running problems and a temperamental engine.

Many people add thickness to the head gasket to temper the compression so the engine runs better.

Barrels are getting harder to get hold of so don’t rebore and shorten the life if not necessary.

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cocorico
Central France
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April 17, 2021 - 10:03 am
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If you envisage 'keeping up with modern traffic', please remember that even a good late model Bantam will struggle to keep up with a modern Learner Legal 125, which may reach the legal limits, but not actual conditions. Any modification to improve performance will probably tend to reduce reliability and possible reduce the future value of the bike. From what I've seen, the market is going for originality rather than restoration at the moment.

That is not to say you can't enjoy riding a Bantam. You just have to choose time and place and hone your riding skills to avoid Joe Public in his tin box.

As Adrian says - they are old and some spares are becoming unobtainium.

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