Please fill out survey real quick on main jet size nt carb only

salorr33cc

Member
Apr 30, 2016
49
0
6
pennsylvania
PLEASE TELL ME WHAT YOUR BEST MAIN JET SIZE AND NEEDLE CLIP POSITION YOU ARE USING AND WHY YOU CHANGED IT,,, ON NT CARBS ONLY PLEASE, ALL INFO WILL BE CALCULATED IN A GRAPH TYPE FORM TO HELP EVERYONE WITH CARB SETTINGS WHILE USING THE NT CARB...ALL INFO WILL HELP THE MOST,,, EVEN YOUR ELEVATION IF IN HIGH AREA..

And briefly tell what is done to your engine ,,,, like exhaust type and picture or description,, light to heavy porting and polish,, PISTON modifications for piston port engine or piston REED valve engine,, what type of HEAD your using,, stock or aftermarket CDI,,

Any and all info will help like your stock came with bike MAIN JET SIZE(70 ish +/-))))) and what you are using now plus needle clip slot position and what modifications were done that you had to change MAIN JET and NEEDLE SLOT.....

Thank you all info will be calculated to try to help everyone with proper jetting..!!!!!!

picture shows old 4 slot needle and slide which is shorter then NEW 5 slot needle and slide......
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,616
422
83
Los Angeles, CA.
Jetting is never consistent in these engines... two brand new engines from the same factory often require slightly different jets to make them run their best.... So posting a chart is pointless.

Most new engines require a slightly smaller jet to run their best, but I always advise that you wait until the engine is completely broken in before changing the jet because as the engine breaks in it will start to run better & better every day, & the jetting will change as it does.

Whenever you add a reed valve, you must jet way bigger!!!

Another thing I recommend is to add all of your 'performance parts' first, & then re-jet, because every time you add a new part (like a pipe or high comp head) the jetting will change.

Last... be careful not to jet any engine too lean!!! It will feel like its kicking a$$, but you're actually burning it up!! Always stay slightly on the rich side just to be safe.

A good way to tell if you're real close to the right jetting is when the engine feels a little 'sputtery' on flat ground & then suddenly feels crisp & strong when you go up a hill.

Most guys here call the sputtery feeling '4-stroking'.

When you have it like I described above?, switch to one jet smaller & STOP THERE!!!
DON'T KEEP JETTING SMALLER!!
 
Last edited:

crassius

Well-Known Member
Sep 30, 2012
4,032
156
63
USA
It is very rare to find one of any of the carbs that come with kits that have a size marked.

I use the NT clone with chinese chars on it and have never had to replace a jet or move a needle setting in the last couple years.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
16
0
memphis Tn
^^What they said.
Every engine is different, even from the same maker.
And even if the chinese stuff WAS stamped, I would not trust the markings.
I've ordered .69 mains from several different vendors and none were the same size.
Solder and drill your own for real control.
 

salorr33cc

Member
Apr 30, 2016
49
0
6
pennsylvania
thats what i have been doing,,, solder and drill,,, seems like .68--.69 is the ticket,,, but be even better to lean out midrange a little more than what raising clip does...wish we could change needle thickness,,
 

2door

Moderator
Staff member
Sep 15, 2008
16,326
124
63
Littleton, Colorado
^^What they said.
Every engine is different, even from the same maker.
And even if the chinese stuff WAS stamped, I would not trust the markings.
I've ordered .69 mains from several different vendors and none were the same size.
Solder and drill your own for real control.
Ditto, ditto, ditto.

Published, or marketed jet sizes are nebulous at best. It would serve no purpose to list jet sizes because depending on where you bought them, or what time of the month they were offered, jet size means little. What one vendor calls a #68, another will sell it as a #70. Due to their source there is little standardization with motorized bicycle parts.

Solder and drill. That's the only way you'll know what size orifice works best for the engine in question.

Tom