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Old 12-15-2007, 10:06 PM   #1
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Default motor tuning question....

lets say you tune your motor on say a day that is about 40~50 degrees... and you do it by the pinch test on the fuel line, and it runs good and you think you have a good tune... then you go run it on a colder day, say 20 ~30 degrees and it does not idle fast enough and dies, does this mean you have to lean it out to get the idle correct? or should you turn up the idle ?
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Old 12-15-2007, 10:33 PM   #2
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Once your idle gap is set, you should never have to touch it again. It will always be low and high needles that need a tweak for ambient temperature changing.
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Old 12-15-2007, 10:38 PM   #3
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Originally Posted by SteveJa View Post
lets say you tune your motor on say a day that is about 40~50 degrees... and you do it by the pinch test on the fuel line, and it runs good and you think you have a good tune... then you go run it on a colder day, say 20 ~30 degrees and it does not idle fast enough and dies, does this mean you have to lean it out to get the idle correct? or should you turn up the idle ?
just lean the low end about 2 hours and try it...if it needs a bit more go a 1/2 to 1 hour at a time, keep a close eye on the engine idle temps...

like soapy said once the idle gap is set you should never have to touch it again...
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Old 12-15-2007, 11:05 PM   #4
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Could he just simply put in a smaller restricter.?
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Old 12-15-2007, 11:10 PM   #5
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Could he just simply put in a smaller restricter.?
well not really...the carb has to be tuned for the different restricters also, so its hard to say if one of the restricters would be on tune...
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Old 12-15-2007, 11:11 PM   #6
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well not really...the carb has to be tuned for the different restricters also, so its hard to say if one of the restricters would be on tune...
Ok thanks.
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Old 12-16-2007, 09:53 AM   #7
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this is good to here.....


does anyone have the link that said what to do with your motor tune when the weather changes, it said some like this.... when the temp goes up you should (richen or lean) when the temp goes down you should (richen or lean) when it is more hummid or less hummid you should (richen or lean)


it was a really nice and cool page that had some good info on it


Thanks for all the help
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Old 12-30-2007, 12:06 AM   #8
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i have seen that card you are talking about, there is a link to the page where it is on the forum somewhere, i just cant remember which topic it was under, ill see if i can find it again...
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Old 12-30-2007, 12:17 AM   #9
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go into nitro off-road and skip to page 9 and you will see a topic saying motor tuning guide, click on it and its the second reply that has what you are looking for.
too easy mate
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Old 12-30-2007, 01:25 AM   #10
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Guys the best thing to do is richen all needles a bit and retune.
That's what i do every time i go out to play or race.
It's very difficult to hunt down a tune when you don't know where you are at.

The "map" you are looking for won't tell you much...that's just the theory. In reality things work a bit differently...!!

Take just 3-4 minutes from your time at the field or track...warm the engine at rich settings and retune.
Most of the times i only richen up the high speed needle...warm the engine up by driving slowly...and then tune that needle...then i check for my idle and low speed needle which most of the times is spot on!!!
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Old 12-30-2007, 11:01 PM   #11
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In general temp and humidity variations go like this:

Colder air is denser. Therefore you have to richen the needles.
Wamer air is less dense. Therefore you have to lean the needles.

Humid air is less dense. Therefore you have to lean the needles.
Dry air is more dense. Therefore you have to richen the needles.

I don't have a way to tell you how much to change for <x> degrees of change or <x> percentage of humidity change. What I know from my V-Specs is that they're not very sensitive in that regard. I might have to change up to a quarter turn when going from 70 degree air to 40 degree air. I've never felt the need to change tune due to humidity.

If you run at different tracks, you're going to want to retune anyway due to the different track layouts. Don't be afraid to just try needle changes to see what they do. Starting from pig rich on the high end needle and leaning down until the motor is REALLY singing (then backing off of that about two hours) taught me a LOT about my engines. I found out I have a 120-150 degree window (4-5 hours) where my engines run from good to great.
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