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Carb. tunning???
Posted: Mon Apr 16, 2007 7:18 pm
by silverbullit
I just got done running sevral tanks of fuel through my .21 in my buggy today. It went quite well after buying a heet gun and hooking my pos starterbox to a car battery LOL.......thanks for the info. Dan.
anyway, after brake in. I started to do a lil tunning about a half tank at a time with running temp. above 200 deg.F
It runs great but when I come off the throdle and let it sit it idles high for about 3 to 4 sec. then drops to a respectable idle. is this normal?? if not wich direction should I go with it?
any info would help. thanks

Posted: Mon Apr 16, 2007 7:40 pm
by mrgrinsters
does that carb have a midrange needle or just the low and high speed needles?
Posted: Mon Apr 16, 2007 7:45 pm
by silverbullit
yes, it has a mid. but, I havent toucht it yet. still fiddelling with the low end.
Posted: Mon Apr 16, 2007 8:05 pm
by mrgrinsters
ok i know i hate touching the mid range needle myself but it could be that it might be a touch on the lean side try turning it just a very small amount to the the left if you can't get it to work with the low end in my unprofesional opinon and i could be wrong unless someone else might have better knowledge of this
Posted: Mon Apr 16, 2007 8:10 pm
by Jato Too Fast
be very very very stingy on turning this needle!!!!!!!!!!!!!!
Posted: Mon Apr 16, 2007 8:14 pm
by silverbullit
Jato Too Fast wrote:be very very very stingy on turning this needle!!!!!!!!!!!!!!
by "stingy" to you mean alot or alittle?
Posted: Mon Apr 16, 2007 8:37 pm
by mrgrinsters
yes indeed stingy is the key a very tiny amount
Posted: Mon Apr 16, 2007 9:04 pm
by SIRMAXXALOT
My opinion is NEVER touh the mid needle? It is set at the factory and I NEVER mess with it. Sometimes it is an air leak that does it--even with a NIB motor like yours or the throttle is just not returning that extra little bit until it sits there for a second, a lot of guy's run a throttle return spring just because of this symtom.
Posted: Mon Apr 16, 2007 9:33 pm
by Tice
DON"T TOUCH IT!!!!!!!!!!! I have yet to see anything good come out of a motor with the midrange adjustment....Unless you count a smoooshed low speed needle. As a matter of fact one motor manufacturer had a midrange needle but told you not to touch it.

CHRIS, help the Bullet out..Chris knows all!!!!!!!!
http://www.rchobbies.org/cars_eng-tuning.htm
or try this site. I believe the "too lean low speed is the cause", try the pinch test.
Posted: Mon Apr 16, 2007 9:58 pm
by SIRMAXXALOT
thank you for confirming that sir
Posted: Mon Apr 16, 2007 10:42 pm
by gubbs3
Ditto- Don't touch the midrange. What you have is still likely a rich low end. An overly rich low end will cause the engine to idle high after coming off of a full throttle run for a few seconds and then drop rpms after a few seconds. Lean the low end until the engine has a steady idle after coming down from high speed. Then if you let it sit and it increases rpm, you are too lean.
Posted: Mon Apr 16, 2007 11:37 pm
by silverbullit
thanks for the info EVERYONE!! it will be well noted in my study of NITRO!!!:D

Posted: Tue Apr 17, 2007 1:31 am
by Kevin/Jabber
Great post with the website tice, I think im going to have to read it!

Posted: Tue Apr 17, 2007 2:25 am
by BigRed
Kevin/Jabber wrote:Great post with the website tice, I think im going to have to read it!

Yes that is a good article. I will sticky this thread because of it:)
Posted: Tue Apr 17, 2007 5:32 am
by Hammer
Bullet,
DON'T TOUCH the mid! PERIOD!!
Of all I read Troy has a finger on it.
In order to play with the mid you must understand what is happening. The MID range needle is essentially an adjustable seat for the low range. If your motor seems to run, idle, accelerate, and has power but it seems to have trouble transitioning from the middle to the top end that would be the only time to play with it.
If your low is fine and you want to add a little fuel in the middle as you turn it you are pulling the "adjustable seat" away from the low needle so to keep everything the same you must follow the middle amount with the low by turning it in.
You will NOT be leaning the low but rather keeping it the same. If you don't move the low the same as the mid then you are actually richening up the low without moving the low needle.
The factory set the needle for flow to keep it smooth from low to high and any adjusting just play's havok with it and the changes you would make are so subtle it's probably not worth touching unless you need to.
Remember that a new motor will have a few glitches and not keep a set for very long until the break-in is complete and even then the weather will keep you twisting screws but once you have it you should really only have to ever play with the high and just a small amount at that.