Ok so bear with me guys as this might be a long one. I came into possession of a rather tatty looking 1999 NRG Extreme that was in bits, being relativity handy with a tool kit i took a punt at it as it was cheeeeap. She needed a whole new top end and exhaust which was promptly bought and fitted. The head and piston was a standard 50cc replacement kit from 101octane, and the exhaust is a Techigas Q'tre. Once fitted i tried firing her up, with no joy, but after a little fiddle with the mixture and idle screw she sprung to life. (At this point i must ad that the carb did not have a filter on as i did not have one. basically a few parts were missing on purchase and amongst these were the standard air filter.) Now i had her running she was idleing very rough and would bog at the slightest sniff of the throttle, gave the carb a clean (and noted it had a 70 jet in it) and she idled much better but still bogged. I remembered i still had the restrictor in the exhaust so i took that out and refitted, she ran much better now i could even open the throttle a bit, but she would bog after she hit about 4k rpm. Soooo off came the carb and in went a 76 jet and i even fitted a cone (tnt) air filter, fired her up and bingo!! i could wind the throttle right open and no boging at all!!! With this now happening i rolled her of the center stand and wound her open again, rev went up .....and up....and up and she started to move and instantly bogged again!! Ok so the revs went super high with no moving, my instant thought was light rollers and i wernt wrong. she had 4g rollers in, also noticed that it has a polini variator and belt...neither of which look very old at all. Replaced the rollers with 6.3's as i understand this is around the standard roller weight on and NRG of this year, while i was in there i had a look at the clutch, springs and contra spring.....all look standard Put her back together ready for another try: So just to recap this is her current setup. standard 50cc head 17.5 phva carb with a 76 jet standard clutch, springs and contra spring polini variator with 6.3g weights And now to test her.....WE HAVE MOVEMENT......ah balls!!! she pulled of from around 3k rpm but as soon as i got to about 5.5k rpm she bogged again *sigh* AN so here is my question, do i go bigger main jet as from reading around on here is seems that 76 main is quite high for a standard head and low level sports exhaust? seen a few post stating that the brass disc in the carb helps with atomisation yet according to here this ped didnt have one, iv also read a blog on pedparts that stated that with an open cone filter the NRG could require upto a 120 main jet?!?!?!?! so just i just keep up jetting till i get it sweet or do i start looking else where for the cause??
Cool cheers for the reply, its what i thought but i just wanted make sure that i was not chasing a unicorn by just continually upjetting. Once i have it close i can look more into the fine tuning of the carb and tranny,
my sym jet, its running a technigas trek pipe full derestrict , a stock airbox and it has an 80 mainjet fitted . im going to say your needing a little more fuel than you have . as a test, remove airbox/filter , start bike and start to add in throttle, when the bike starts to stall out pop a couple finger over some of the open end of the carb to decrease air amount, you may fine rpm raises and thats telling you your running lean on mix ie needing a mainjet increase
ok im gunna need quite a bit higher then if its got and open foam filter, i did want to put a standard filter box on there but changed my mind when i started looking at the price of them second hand on ebay. Have a polini jet kit already purchased just incase with jets up to 98 so will get on it over the weekend once i have fixed the puncture in the front tire
Well managed to get an original airbox for a tenner and its working much better now. got up to a size 98 jet with the cone filter and it still wanted bigger. now i have to jet back down again for the box Only thing missing from the airbox is the little snorkel that connects from the box to the frame, im going to assume that dont matter so much. Also put the 4g roller weights back in and the revs sit bang on 8k during acceleration which is perfect for the Q'tre exhaust
