67cc big bore for nq50 ??

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67cc big bore for nq50 ??

Post by Brodymartin73 » Wed Mar 20, 2019 1:47 pm

Found some big bore kits on eBay is there anything I should know or to stay away from this kit ? New to the spree world .1985 nq50 spree
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Re: 67cc big bore for nq50 ??

Post by eclark5483 » Wed Mar 20, 2019 8:41 pm

Plenty you need to know before even thinking of buying a kit, link is in my signature.
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Re: 67cc big bore for nq50 ??

Post by motormike » Thu Mar 21, 2019 12:41 am

The choice to modify a Spree engine is a poor one.
The better choice is to modify the Spree chassis by adding a
AF16 and assorted goodies to make it a much better bike in the end
without spending a bunch of cash to end up with a non-variated Spree engine.
imho... :urban:
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Re: 67cc big bore for nq50 ??

Post by kuromi » Tue Mar 26, 2019 6:00 am

+1 Motormike's comment :thumbsup:
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Re: 67cc big bore for nq50 ??

Post by Meatball » Tue Mar 26, 2019 6:35 am

The biggest performance gains you’ll get from modifying a Spree motor comes from the substantial weight reduction of your wallet.
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Re: 67cc big bore for nq50 ??

Post by Wheelman-111 » Wed Mar 27, 2019 3:23 pm


I believe I understand the position BrodyMartin73 is in; You have the Spree, with a worn top end, the kit is cheap, and it'll be kinda fun to install it and experiment. Chances are that the displacement bump will provide a welcome increase in power if you can get it to work and last. A couple of essential hints on the Affordable Chinese kits to keep in mind:

1. Feel the edges of the ports in the cylinder. If your finger comes out bleeding, use a fine file to chamfer the port edges so they don't slice the oil off the piston and create a dry spot. Also this decreases the chance of snagging a piston ring.

2. Don't count on the piston/cylinder clearance to be accurate. Sloppy fit is safer than too-tight. If the measurements don't compare to Honda's specs, AND the fit is Tight, consider honing the bore - preferably under headbolt compression - until that critical measurement is right. If the clearance is Loose, see Item 1.

3. Exercise great care installing the piston pin clips. The Chinese metal is reputed to be soft, and if you exceed its elasticity there's a significant risk of having one pop out underway - with catastrophic results.

4. You will need a bigger main jet and that alone may not be enough to handle off-throttle heat spikes because you can't enlarge the low-speed jet built into the PA carb. Crank down the air screw - like maybe a half-turn out from lightly seated, and hope for the best.

Let us know how it turns out.
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