Difference in Carbs

S

Scootershack

New Member
I was watching a youtube video the other day on the three different types of carbs for these babies..Im looking at buying a high performance carb for my 48cc bike. The guy in the video says that there isn't much difference between the 48 and 66cc high performance carbs. Im skeptical on getting the 66cc carb because I don't wanna ruin my bike. So question is, can I get the 66cc carb or not. Thanks a lot.
 
The Carbs are the same physically its the main jet inside that is different. What the 66cc means is the main jet is sized for a typical 66cc ht engine. What a lot of members including myself have found is your engine may run ok with that carb as it is. I had to drill out the jet on mine to get the right mixture and spark plug color. So the best think I think to do is try it first and go from there.
 
The 48cc and 66cc motors are very much the same, as carbs go you can use the same carb on both motors, however, the carbs may need to be jetted differently to run well on each respective motor. Tuning a carb is a balance, there are other issues at play like the dampening of the particular exhaust and air filter that will effect how a carb needs to be adjusted, so it may work well right out of the box and may not.... Also, keep in mind that you will likely need a new/different throttle cable when changing carbs....
 
Funny great minds think alike! Just kidding N/C we probably were responding at the same time.
 
actually, it depends on which carb you buy.
if you buy an nt carb specificallyfor a 66 c.c. engine, and you want to put it on a 48 c.c. engine, it MIGHT be jetted a little to rich for the 48. but as far as i can tell, all of these carbs are jetted the same. they are all jetted for the 66 c.c. engine.
even tho it specifically says "66 c.c. carb" it;s just like the ones that go on the 48 c.c. engines.

if you're talking about the cns carbs, they are actually too big for the 66 c.c. engine (jetting) and it would probably need to be re-jetted for a 48.
But the cns carbs are junk, i wouldn't waste my money.

now, if you have the oddball 48 c.c. china 2 stroke like i have (it doesn't have an intake manifold. the carb bolts right to the cylinder) it has a totally different carb than the n.t.
this is a carb is used for scooters and pocketbikes, which is a totally different design.
the only real difference between a 66 c.c. nt and a 48 c.c. nt MIGHT be the jetting, but i'm pretty sure that all nt carbs are jetted the same, no matter what engine it goes on. they are set up for the 66 c.c. engines, but they put this same carb on the 498 c.c. engines with the same jetting.
I re-jet every carb i put on a bike no matter what, because no 2 engines will run the same.

if you're looking for performance, get the nt "speed" carb, but to get it to run perfect, re-jetting may be in order.
if anyone just bolts a carb on and leaves it the way it is right out of the box, they're not getting all of the potential power out of these engines.
every carb should be torn apart and re-jetted to suit the engine that it's going on.
like i said, no 2 engines will run the same on the same jetting.
you need to jet the carb based on YOUR engine and where YOU live.
yes, the outside air has a lot to do with how you jet the carb to make it run right.
 
It sounds like we all agree that the key to a good running engine is the tuning. You have not said which carb you have or why you want to replace it, you might try some of the mods in the performance section of this forum to get yours running correctly.
 
You guys this is by-far the most feedback ive got on a topic on here, haha, thanks. First off the carb I have on it now is just the standard 48cc carb that comes with the non-upgraded kits you would buy. The only reason I wanted to know about this is because someday I would like to do a build of my own (since the bike I have now I got free) and when I do the build ill probably buy the 66cc motor. What I was thinking of doing was buying a 66cc cns high-performance carb so that I could beef up my 48cc for now and then transfer it to my 66 at a later date. I appreciate all the feedback. Does anybody know of a thread on this site dealing with different jet sizes, where there located ect..thats like the only part on a carb that I havn't found yet. Thanks again.
 
Scootershack;...I was thinking of doing was buying a 66cc cns high-performance carb ......a thread on this site dealing with different jet sizes.....[/QUOTE said:
Well, a lot of people hate the CNS carb and would scoff at you for buying one. That said, I love my CNS carb, my bike runs great, fired up perfectly this year after a complete tear down...
The prices I see for a CNS carb assembly with throttle is kinda high (like $65) and I personally wouldn't shell out that kinda money for one. I think the carb alone is like $35 with the high flow air filter so thats not too bad, but if you change from an NT carb you will likely need to change/adjust the throttle cable to fit the CNS carb. You might need to replace or custom make the throttle cable. (which is pretty easy actually, just mark the required length for the ball end then wrap some bare single strand telephone wire around your mark and solder in place, leaving a ball of solder about the size of the original cable) I would probably just set aside your NT throttle cable and custom make a new cable for the CNS if you go that route. The CNS also has a second cable for the "choke", which is actually an extra enrichment jet. You will need another cable and lever to pull that plunger if you want to use it (not sure if the "carb only" package comes with one or not?)
As far as the jets go, they are available, I think sickbikeparts.com has 'em... That said, the best thing to do if you are interested in messing with the carb jetting is buy a set of mini drill bits, they're only like $5-8 on ebay or amazon for a set. Then you can drill out your jet to whatever size, going step by step to study the effect, until you get it "right". To go smaller you can solder the jet shut and re-drill to a smaller hole, or start with a new jet. CNS carb rebuild kits also come with a complete set of jets (the CNS carb has 3 jets).
If your looking to tinker and learn I would say go for it, otherwise you might just keep your nt running on your 48cc and when you order your 66cc you can just order a kit that comes with the CNS carb if thats the one you want....
If you decide to tinker I'll be glad to help...
Click to expand...
 
Yeah I meant to add on to my last post that After hearing your guy's opinions, Ill probably just stick with NT, especially after reading your post about all that may or may not have to be done...afterall, I am fairly uneducated when It comes to motors. For now I will probably just wait until I start a new build probably a long time from now. Thanks for your time guys.
 
When the NT speed carb -the "66 cc carb" -came out, the specifications given claimed both a larger port and a larger jet- I don't know the specifics, but I know that to be true. I have a 66 Speed carb I'm eventually going to put on my 50 cc build, to replace the "sleeve carb" which has an entirely different irreplaceable jet than the other NT carbs which CAN be reoplaced.

I have one on my 66 with a billet intake- runs really solid, but not performance "crazy" like these on youtube- actually the billet intake made the most difference when I first put it on with the original older "50 cc" NT carb.
http://www.youtube.com/watch?v=VEpxWg8OYCA

http://www.youtube.com/watch?v=w_F7C2k7xNg&feature=results_video&playnext=1&list=PLE5B285EB29DE0E29


but the 50 is running consistently and I'm getting great miles and use from it- I know the performance will improve- so I haven't rushed into replacing the jug to allow me to replace the intake and carb- I've been busy moving too. When I get that together I'll report back.
 
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It was mentioned above, "where you live" but to expound on that, your altitude above sea level plays a part in proper tuning (jet selection). The higher you are the smaller the main jet needs to be and conversely, lower altitudes will benefit from a fatter mix. At 6000' I solder up the stock NT jet and drill them to .024. It seems to be just the right blend of fuel to air for my altitude. Experimentation will get you where you need to be for best performance.

Tom
 
2door said:
It was mentioned above, "where you live" but to expound on that, your altitude above sea level plays a part in proper tuning (jet selection). The higher you are the smaller the main jet needs to be and conversely, lower altitudes will benefit from a fatter mix. At 6000' I solder up the stock NT jet and drill them to .024. It seems to be just the right blend of fuel to air for my altitude. Experimentation will get you where you need to be for best performance.

Tom
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I'm no expert, as others have pointed out but after playing with stock/CNS/NT speed carbs, I have to agree re-jetting for each bike it necessary but careful with the drilling I jumped two sizes bigger and only needed to go one size. I kept adding bigger and bigger jets and only got worse performance, I had given away my stock carb so I couldn't go back. Be patient with the process and realize you can go too big as well as too small.
 
LaLongueCarabine said:
I'm no expert....I have to agree re-jetting for each bike it necessary but careful with the drilling I jumped two sizes bigger and only needed to go one size.
Click to expand...

You give good advice, I would just add that if you end up going too big with the jet you can solder closed the hole and drill it back smaller instead of getting a new jet if you want....
 
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