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  1. #1
    RC poster
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    Oct 2008
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    a little help with tuning ...

    ok i have a t-maxx 3.3 and a t-maxx 2.5 and a rustler 2.5 I switched fuel brands and went with the traxxas fuel 20% which i was running before and now they are hard to start and wont rev up i switched back to the fuel brand that i was running before and still the same thing ..
    i took the carbs off of all three and cleaned and checked the glow plugs and checked the seals and on the 3.3 i went back to the factory settings and it is hard to start and wont idle and i watched the tuning video half a dozen times and still no matter what screw i turn i wont run very well and i was wondering if any one else had this problem and yes i use wd-40 for after run oil and the air filter are clean and when i ran the about a month ago they all run very well ...and also if it does move it wont run past 1/4 throttle and it seems to be smoking like it should... i am at a lost...

  2. #2
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    Jun 2006
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    Central Coast, Cali.
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    I think its time for you to do a leak test. How many gallons do you have on your current engine? Also I would try a new glow plug.
    A lot is two words. Alot is not a real word.

  3. #3
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    Oct 2008
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    ruffly about a gallon and a half and i have a new glow plug in it and i just took the engine apart and i dont see any metal or scoring on the sleeve or the piston.. and it feels like a good tight fit.. and how do i do a leak test i am still trying to learn stuff about this.. and i have the tank off and i plugged on hose and i blew into the other hose and i didnt feel and leaks or see anything leaking out ??? and thanks again...

  4. #4
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    Leak Test

    I don't think the new fuel caused a leak, its just something to look for. If you have raw fuel around the front of your engine that is an obvious sign of a leak.

    Also try being a bit more patient during tuning. Make adjustments slowly.
    Last edited by bikesair; 03-24-2009 at 07:46 PM.
    A lot is two words. Alot is not a real word.

  5. #5
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    i dont have any signs of any fuel around the front or the back side of the engine or any signs of dirt collecting around the engine.. i am going to do what you said and take my time tuning it and i just got a colder and a hotter glow plug to try and also a stock traxxas glow plug to try also and thanks for the help it is very much apperaciated...

  6. #6
    RC Champion
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    Mar 2007
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    western NY region
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    read through this...has everything you need to know about tuning nitro engines...

    here is all the tuning info you should need...be sure to read carefully and check out the links and read them carefully too...

    a general "rule of thumb" when tuning and you lean out (close) your HSN, you have to richen (open) your LSN...this is because when you lean out (close) the HSN it restricts the flow of fuel to the LSN, so you have to richen (open) the LSN to maintain a proper air/fuel mixture & reliable idle...and same applies when when you richen (open) your HSN, but (opposite direction) you lean out (close) the LSN to limit the excess fuel flowing through the HSN to maintain a proper air/fuel mixture...

    so w/that said always remember reset carb to factory settings <~~ when your tune is way off and start re-tuning from there...

    in the following links there are "tuning guides" for nitro engines...they have really good info in them to aid you in the tuning process...and as for tuning, yes the 2.5 & 2.5R & 3.3 are all tuned the same way (incase anyone was wondering)...always tune your needles in this order HSN, LSN then idle, and always tune in the smallest increments as possible, IE: 1/12th or 1/16th of a turn, sometimes even 1/8th of a turn is too big of an adjustment and will pass the "sweet spot" the engine will like to run at...and always begin tuning after you have run through 1/2 of a tank of fuel to ensure the engine is at normal operating temp, and to prevent the dreaded 1/2 tank lean bogging...use a temp gauge for double checking your tune (if one is available, i find the Duratrax FlashPiont <~~ works very well)...and DO NOT tune for a specific temp...ONLY use the temp gauge to make sure you stay UNDER 270 degrees...

    New to Nitro? Helpful Tuning tips. <~~ courtesy of "Nitronaught"
    Tuning Guide #1 <~~ courtesy of "Traxxas"
    Tuning Guide #2 <~~ courtesy of "Traxxas"
    Tuning Guide #3 <~~ courtesy of "RCHobbies.org"

    and finally here is another usefull tip, you can "read" your glow plugs to verify if your tune is good or not...and as for "reading glow plugs"...you should do it after you have ran 2-4 tanks on a fresh plug...then take it out and "read" it...
    here is some more info on reading glow plugs <~~ with illustrations...and here is one more link for Nitro Engine Troubleshooting <~~ for those engines that don't seem to want to start...and here is another for Troubleshooting Engine Problems <~~...and it would be a good idea to bookmark these links for future reference incase you need them, they have allot of great info in them...the last one even goes through finding air leaks and getting that last percentage of the "perfect" tune on the second page of it (tuning guide #3)...good luck!!!...

    also here is a pretty cool nitro tuning flow-chart that someone found online, that i thought i'd post with this to help with diagnosing tuning problems...

    ***image edited to fit traxxas's picture posting standards...***
    the full sized image can be found here <~~...



    ***I DO NOT take any credit for making this nitro tuning flowchart...it was found on-line by another traxxas member...all i have done is print it out, scan it, and upload it to my photobucket account to make it available as another resource/reference to help anyone out that has any tuning problems in which they need help to get corrected...
    "Growing OLD is mandatory, Growing UP is optional"

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