How to reset NS-25 carb to factory specs.

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CRSMP5
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How to reset NS-25 carb to factory specs.

Post by CRSMP5 » Thu Oct 16, 2003 10:08 pm

from HPI's forum

First, set the Idle Adjustment Screw so that the gap is around 2mm. This adjustment is like a doorstop, it prevents the carb from closing all the way. If this adjustment is set too small the idle speed will decrease and/or the engine will shut off when you apply brakes. If the gap is too big your idle will be too high. Clockwise (CW) = bigger gap.

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Second, adjust the Low Speed Needle. The key point is that the low speed needle must be adjusted with the carb in the closed position. If you don't hold the carb closed, the low speed needle will force the carb to open as you turn the screw, which is probably why it seems like it turns more than 3 revolutions before it is closed. To adjust it correctly, you can use two different techniques. Technique #1 is to hold the carb closed gently, then watch for movement in the carb gap, as soon as it starts to open you have found the fully closed position. Technique #2 involves holding the carb closed very firmly, either by hand or with the carb linkage. If you hold it tight enough you will be able to feel resistance when screwing in the low speed needle, when it feels harder to screw in you have reached the fully closed position. Don't overtighten it, the tapered needles inside the carburetor will be damaged if you force it too much. From the closed position, the suggested starting point for the low speed needle is 3 turns. Adjust in 1/8 turn increments depending on conditions. Once the low speed needle is set, you shouldn't need to use it for tuning, rely on the high speed needle adjustments for most of the tuning. Clockwise (CW) = lean.

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--or--

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The last adjustment is the High Speed Needle. To reset it, close the carb and then screw in the high speed needle gently until you feel resistance. Don't overtighten it, the tapered needles inside the carburetor will be damaged if you force it too much. From the closed position, the suggested starting point for the high speed needle is 4.5 turns. As the engine breaks in, the high speed needle will probably need to be set lower, 3.5 to 4 turns depending on conditions. We suggest using a digital temperature gauge to monitor the engine, keep the temperature under 300 degrees. Always tune the engine when it is fully warmed up, tuning a cold engine will result in a lean setting once the engine is warmed up, which could damage the engine. Tune the engine so that you see a trail of smoke coming from the exhaust at full speed with a warmed up engine. If you don't see a trail of smoke, richen the high speed needle 1/8 turn CCW. Clockwise (CW) = lean.

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Note: All engines and conditions are different. Factors like the type of fuel you are using, altitude, humidity, temperature, glow plug, engine condition, air filter condition etc. make it impossible to give a "perfect" setting for tuning the engine. You must adjust the carb settings according to your conditions.
Last edited by CRSMP5 on Thu Nov 27, 2003 9:52 am, edited 1 time in total.

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FlashRC
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Post by FlashRC » Thu Oct 16, 2003 11:39 pm

Sweet, very useful information CRS.

Steve
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Post by SavageSSOwner » Sat Oct 18, 2003 10:58 am

Yeah, thanks alot!!

SS

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Post by Badger » Sat Oct 18, 2003 12:39 pm

Thats a great post! My bro and friends have had that problem of setting the carb, I will pass the info on! Thanks!

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tuna
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Post by tuna » Wed Oct 29, 2003 3:30 am

CRSMP5, What a great post, I've learned a lot from the information you have been posting, thanks.......... By the way, did you trim your fingernails for these pictures too....LOL, Peace

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cduna
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Post by cduna » Thu Nov 06, 2003 10:02 pm

I cant say enough about this posting helped me out a great deal . Keep up the good work .


:lol:

Chris

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