steven16

ok i just put this carb on a engine i finally got to work so now how do i tune it ? right now it runs really rich {for breakin} but after when i want to tune for power whats the basics that i would do. the carb is of a cheap no name engine and the engine im runing is a cen nx 76 which probly doesnt matter because its a mix match kind of thing
steve

silverman1

My reccomedations, don't mess with the third screw. Start leaning the high speed screw out first after your satisfied with your break in process. Tune your high speed needle with a half tank of fuel and warmed up. Continue to tune through the high speed tuning process until you get no more performance gain on top end. Richen the the high speed needle by 1/8 a turn, make sure your getting decent smoke, if all is well there move on to the low speed needle screw. after having her warmed up, bring her in and pinch the fuel line, if it dies right now, richen the low speed slightly by 1/8. If you pinch the line and it revs up real slowly at idle 3 to 5 seconds, lean the low speed up an 1/8.

Make sure your throttle slide it set correctly before doing these adjustments, you know the gap at idle.

Also take your time doing these adjustments 1/8 at a time and give it a chance to adapt to the adjustments.

I don't know much about the third screw, all i know is if you adjust it you'll need to adjust your low speed screw. If its set at factory settings leave it alone.

good luck

DaveG55

What do you mean by a "3 screw carb"?
Most carbs for rc vehicles are three screw HSN, LSN, idle screw
BUT some are 4 screw HSN, LSN. mid range needle and idle screw. The 4 screw one is oftenrefered to as a 3 screw carb. If you've got the first variety then adjust the HSN first, then the LSN and finally set the idle.
If you have the latter carb then do not adjust the mid range needle as it is very difficult to get set properly and does not really need any adjustment for normal running.
Here are a couple of tuning videos that are good guides to nitro engine tuning
http://www.youtube.com/watch?v=oSmMzpZM_As
http://www.youtube.com/watch?v=BJFsJAxNoRg

NitroDemon18

Don't tune the middle needle, it should be set fine. Just tune the low and high speed needles.

SAVAGEJIM

I agree. Dont even mess with the middle screw. Return it to factory position and only tune the high and low needles.

I have no earthly idea why engine makers even make a middle screw; it is merely the hole the LSN closes into. On a two needle carb, the "middle" needle is just the fixed hole that the LSN goes into as the carb opens and closes.

steven16

its a 4 screw carb it adjusts how much of the low speed needle is showing at all stages of throttle but i dont know factory settings so i just kind of measured and compaired it to my normal 3 screw carbs and it came out to be flush and my engine runs so i guess it will work there

SAVAGEJIM

Flush would be a good place to start and just tune with the other needles. That is, if you dont have the owners manual or the website does not mention factory settings. I personally would hit the CEN website and download the NX76 manual.

steven16

i would but this carb isnt off the cen motor it off a nother motor and i put it on the cen motor so it wold run right so i was tryin to figure out the basics but flush seems to work so far