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Old 06-11-2016, 08:18 PM
Nashville Kat's Avatar
Nashville Kat Nashville Kat is offline
Motorized Bicycle Elite Member
Join Date: Apr 2009
Location: Jacksonville, Florida
Posts: 1,403
Default Re: Help a Veteran with New engine crackiling and 4-stroking

Looks to me like a standard 66cc China Girl.

If you have an older stock carb- those were built originally for the 50cc mortors-

when I did my first build in 09- that was the setup- 66 motor original stock NT carb-

EVERYBODY on here was complaining of bogging down at full throttle- CNS and other cabs were just coming out-

My own solution was found when I put a straight billet intake on- that cleared the four stroking

The NT SPEED carb came out then- Marked with the word "Speed" and generally with the carb shut off valve also- that also helps for the larger 66 motors- an upgrade built specifically for the larger version.
That's all I've ever run. The Speed carb runs well on a 50cc too.

also BEWARE of brushing CHOKE lever on- I've done this a couple of times - not terribly close together, and then wondered why the bike was running sour- a choke lever on perpetually will big it down too.

A smaller back sprocket would give you better speed, but more importantly not so much rev and vibration at a cruising speed- some 1.75 street tires or even 1.5 would give you a better roll, if you're not on rough roads, but they do wear just a bit faster.

A 415 Industrial/Trike chain is the same size but with smaller profile- half the weight, and much les rolling resistance.

Can't tell you much about porting- I think the easiest and most powerful purchased item would be a cylinder jug with a wide 40mm intake and then a billet intake to match, and Delloto style or CNS carb. But haven't tried one- my cruiser with 700c wheels and 34 sprock will cruise at 30 and can get to 35 not quite fully opened. And that's fast enough here.

Last edited by Nashville Kat; 06-11-2016 at 08:30 PM.
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