NRG 70 running very bad after fitting stage 6 exhaust?

njanoskis · L Plate Warrior Joined: 11 Jan 2015 Karma :

Hello, I have a 2010 NRG Power with stage 6 70 kit, running a 21mm TNT carb with 72 jet and 4g rollers. I changed the exhaust (wasnt standard but definitely not a performance one) to a stage 6 pro replica exhaust and now it just doesn't run right at all.

Very slow from take off to about 5000rpm, followed by a surge of power mid range accelerating fast and revving its tits off for about 3 seconds, then suddenly drops down again and sits at just under 8000rpm at around 30mph. Before it would uniformly rev up to around 9000rpm with good acceleration.

, i know it must be to do with rollers, clutch springs, etc but i havent got the money for trial and error so any info on the general types needed would be appreciated

evoboy · World Chat Champion Joined: 20 Aug 2009 Karma :

Needs lighter rollers. Trial and error is the only way you can do it when tuning the gearbox on a scooter.

The rollers in it may also be flat spotted.

The belt may also be due a change.

It may also need heavier clutch springs.

72 main jet seems very small on a 70cc kit and 21mm carb. Are you running an airbox?
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mospeed · Renault 5 Driver Joined: 26 Dec 2012 Karma :

I assume that you have removed the restrictor...

njanoskis · L Plate Warrior Joined: 11 Jan 2015 Karma :

rollers arent flat spotted, yes the restrictor is removed and i am running standard airbox with malossi sponge

njanoskis · L Plate Warrior Joined: 11 Jan 2015 Karma :

by heavier clutch springs do you mean stiffer? and from what ive seen on the internet 72 jet seems to be a fairly staple size to go for

BMWilliams · Two Stroke Sniffer Joined: 08 Jan 2015 Karma :

Find out what the standard jet size was then upjet to suit the parts just to make sure you have the right size to lessen the risk of running lean and seizing your lump

70cc Kit - 10-15% upjet
Exhaust - 5-10% upjet (depends on exhaust, some have been known to need up to 15%!)
Open Filter - 5-10% upjet

The new exhaust should have a set of rollers with it, 9/10 these normally help, if not buy a set of diff size rollers lighter than the ones you have, sounds like it needs lighter ones, not too light though, as it may affect your top speed

Trial and error though with the rollers and clutch springs
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