How To Guide NT Carb Tuning Basics



beetleman

New Member
Joined
Aug 8, 2016
Messages
29
Well after a long winter hibernation, I started the bike and went cruising. And to my surprise the engine is giving me a hard time.. even though no changes were made over winter. At first I thought it was bad fuel, but there was very little fuel in the tank and I filled it up with fresh fuel which surely diluted the little that was in there.

Basically the engine quits in neutral. As long as I give it gas it goes, and goes strong. But if I squeeze the clutch, as soon as I let go of the throttle the RPMs drop to a stop. The throttle barrel needle, even when turned in all the way, does nothing. So I turned the throttle adjustment screw (top of carb) counter clockwise for more open throttle at idle. That did give me a way too high RPM at throttle, but even with that it slows down and cuts.

My mixture E-clip is at the top notch and I currently have a 0.61 jet (this setup stopped the 4-stroking I had experienced last year).
Are these all symptoms of a too lean setup?
 

gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
3,947
these are symptoms of the gas that was left in the bowl of the carb over winter turning into lacquer. Take the bowl off the carb and clean it out along with the jet and float needle.
 

happycheapskate

Active Member
Joined
Nov 5, 2009
Messages
1,392
It’s probably bad/separated gas. If that’s not the problem...Check for leaks at the intake to block gasket and carb to neck gasket by squirting very soapy water in those spots. If it’s sucking you’ll need to twist the throttle and see if it bubbles or ripples anywhere. You can also drip gear oil there instead to see if it idles better.
Well after a long winter hibernation, I started the bike and went cruising. And to my surprise the engine is giving me a hard time.. even though no changes were made over winter. At first I thought it was bad fuel, but there was very little fuel in the tank and I filled it up with fresh fuel which surely diluted the little that was in there.

Basically the engine quits in neutral. As long as I give it gas it goes, and goes strong. But if I squeeze the clutch, as soon as I let go of the throttle the RPMs drop to a stop. The throttle barrel needle, even when turned in all the way, does nothing. So I turned the throttle adjustment screw (top of carb) counter clockwise for more open throttle at idle. That did give me a way too high RPM at throttle, but even with that it slows down and cuts.

My mixture E-clip is at the top notch and I currently have a 0.61 jet (this setup stopped the 4-stroking I had experienced last year).
Are these all symptoms of a too lean setup?
 
B

Beetleman217

Guest
these are symptoms of the gas that was left in the bowl of the carb over winter turning into lacquer. Take the bowl off the carb and clean it out along with the jet and float needle.
Nah, I checked and the gas in the bowl looks fresh. There’s no lacquer or any sign of tarnish. The engine sat for no more than 3 months over the winter. Besides, I since rode it 8 miles with new fuel in the tank so a lot of gas went through the carb already.
 

beetleman

New Member
Joined
Aug 8, 2016
Messages
29
these are symptoms of the gas that was left in the bowl of the carb over winter turning into lacquer. Take the bowl off the carb and clean it out along with the jet and float needle.
Nah, I checked and the gas in the bowl looks fresh. There’s no lacquer or any sign of tarnish. The engine sat for no more than 3 months over the winter. Besides, I since rode it 8 miles with new fuel in the tank so a lot of gas went through the carb already.
 

Frogslayer

Well-Known Member
Joined
Jan 20, 2019
Messages
855
The bowl being dirty has little to any effect on how it runs, it's the little stuff moving into the jet that screws you over. It needs to be medically clean, they are so small one little grain of sand will change your fuel mixture and cause it to run like crap. Take the jet out and make 100 percent sure it's perfect.
 

Frogslayer

Well-Known Member
Joined
Jan 20, 2019
Messages
855
Finally got around to jetting. Looked for a little bit on eBay, couldn't find a jet set 65 to 70 in increments of 1 so i tried the solder shut and drill out. Got the $3.99 micro drill bit set at harbor freight today. I measured in mm since it's a Chinese carb and bad conversions are what took out that space shuttle that one time. The kit says .5mm .6mm and .8mm. seems this wasn't what was in the kit at all lol. The biggest bit i could fit through the jet measured .56mm. my next biggest bit in the set measured .76mm but wouldn't go through the hole in the jet. So i soldered the jet shut and went with the .56mm thinking if it's too lean I'll have to ream the hole a little or break down and order a legit jet set. Took her for a cruise and so far it's way better. Runs smoother at low rpm and revs higher easier than it did before as well. Wish i would have done this a long time ago. 1355' above sea level is my attitude of anyone is wondering. 72 degree semi humid day for the weather. Rooster crowed 3 times this morning, he usually just does 2.
 

extremeodd

Active Member
Joined
Mar 30, 2019
Messages
287
Finally got around to jetting. Looked for a little bit on eBay, couldn't find a jet set 65 to 70 in increments of 1 so i tried the solder shut and drill out. Got the $3.99 micro drill bit set at harbor freight today. I measured in mm since it's a Chinese carb and bad conversions are what took out that space shuttle that one time. The kit says .5mm .6mm and .8mm. seems this wasn't what was in the kit at all lol. The biggest bit i could fit through the jet measured .56mm. my next biggest bit in the set measured .76mm but wouldn't go through the hole in the jet. So i soldered the jet shut and went with the .56mm thinking if it's too lean I'll have to ream the hole a little or break down and order a legit jet set. Took her for a cruise and so far it's way better. Runs smoother at low rpm and revs higher easier than it did before as well. Wish i would have done this a long time ago. 1355' above sea level is my attitude of anyone is wondering. 72 degree semi humid day for the weather. Rooster crowed 3 times this morning, he usually just does 2.
For drilling, this set is awesome
https://www.amazon.com/gp/product/B000TY190C
It's sizes #61-#80 which equates to 34 to 99 jetting in approx 3-4 jet size increments. For the 60s it should do 61, 64, 66 however because they are drill bits you can always waller out the hole a touch and have every possible size with just this cheap set.
 
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