But i guess it was fun while it lasted! I think I might of hit 60 mph on that thing.
If it ain't broke, don't fix it.
Running a very lean engine caused mine to make "A" great run,when I applied brakes the idle'ing climbs and then the engine dies.
Then back to the drawing board run it rich and and go from there again. Still not purrrfect but getting there.
I think the key here is "PATIENCE"
I think i finally have it. I just ran 2 tanks out didn't get hot, plenty of smoke, starts pretty good off the line. I think the LSN needs to be a 1/16 leaner and I'll have it. Boy it was flying tonight.
TMaxx 2.5 with 72 RRP spur gear.
I bought a 2.5 used and it ran fairly well, but had problens trying to fine tune. I was unable to repeat the running quality when making adjustments 1/16 up then putting it back the same 1/16 turn. I noticed that the dust bellows over the carb was cracked and brittle, and there was play in the carb throat, so I got the rebuild kit and rebuilt the carb. Now I can't get it to run at all.
It started several times but shut down, then trying to start would flood the muffler with fuel. I believe that it is getting way too much fuel at the 4 turn setting but all the adjustments I have made seem to be in vain, (near the factory settings).
I did note htat the HSN has a gouge down the thin part of the needle, could this be creating my problems?
2.5 new Horst
If it was running well (more or less) before you rebuilt the carb then you probably need to go through the tuning again. If you eliminated air leaks and now it wont run, or runs super rich, that may indicate a blockage in the exhaust pipe. Take it off and inspect it from both ends making sure the exhaust tip is not clogged.
"Fortunately son, I says fortunately I keep my feathers numbered for just such an emergency!"
Well it is nice to see that I am not alone. Recently bought a sportmaxx and the truck seems to run really well, except after running a few minutes, it will stall out once you let off the throttle. Obviously not a new issue. Before I read the post in the forum, I thought that the truck was loading up, or flooding itself. Seems like a lot of unburned fuel coming out of the pipe. So I leaned out the High speed valve about a quarter turn, but really no difference in duration. I then read some the post on this forum, proceeded to adjust the low speed, out about two turns, made sure the brass nut on the HSV was tight, tightened the gas lid to make sure it wasn't sucking air, and still have the problem.
When I first noticed this was a problem, i thought maybe the truck was overheating, because if I let it sit for five minutes, it will start up, but it will not start right after is stalls. So now I am unsure what to do, lean it out, richen it up, adjust the LSV, or even the idle. I will keep trying different combinations, but if someone who has been through this has any other ideas, I would appreciate it.
I did also put a new glow plug in it and I am running fresh fuel. I also zip tied the air filter. Right now I have been going between 4 turns out and 3.5 turns out. On the LSV, i am two, 1.75 out. I am hoping it is not a bad engine because the three or four minutes it runs, it rips. Then at the end of the run, it starts to bog and then if I let off, it stalls. Thanks for any tips.
how fast would would the 2.5 engine go if you got it ported?
R.I.P Eric(Eazy-E)Wright 1963-1995
I also am having problems!
I got a new Sport Maxx with the 2.5 a few weeks ago, followed all the instructions for break in etc. and I have had about half a gallon of fuel through it so far.
I have the problem where it will run for 5 mins then stalls and overheats.
I have tried the tuning guide and according to all indications it is actually running rich but still overheating.
The only time it ran for more than 5 minutes was on a really windy day which was enough to keep the engine just cooler than steaming hot.
I have had plenty of air holes cut in the windshield etc. but still no luck.
I have plenty of smoke so pretty sure it's not running too lean.
Have you guys seen this document >>>
It seems I have the symptoms of a worn piston/sleave but this engine is supposed to be brand new!
The only way I can run it reliably is to run it really slow, any full speed passes for more than 3 seconds and it overheats straight away.
Any help would be much appreciated,
I stumbled on this forum trying to find out why my throttle will stick open sometimes even though the servo is back to idle position. I even put a throttle return spring on to insure it came back only to find I sometimes I still have the problem. I have found that if you manually snap the throttle it will sometimes cure it. However, this does no good when she's wanting to run away! I got so interested in what was being talked about here I read the whole darn thread and after reading it I found, I too wanted to post my thoughts and findings on the TRX 2.5.
I read the document listed above and would have to agree with with Traxxas. In the short amount of time (2 months) that I have been messing with this "Nitro Thing" I have found that I need to learn "my" engine because not all engines are made the same, close but not the same. I have been doing machine work for 20 years and fully understand how all this works. Another thing that I'm learning is this is not a hobby for those that want it right now. I would also have to agree with Ron Paris, that learning to tune is the hard part. I'm sure the pro's have gone through their share engines and glow plugs. For those well experienced folks with plenty of engine knowledge who are having problems with this engine, Are you used to and like one brand of engine? I only add this because when your used to working and playing with a Chevy it's hard to bring us around to Ford, no matter how good it may be or via a versa! On the flip side you also know when something isn't right! And for that Traxxas seems to want to work things out. Heck, it's in their best interest unless they want to get out of this business!
The one problem that I did struggle with is the blue smoke issue. I have found that if the engine is not running hot enough (lean) there will be little to no blue smoke (not enough heat to burn the oil) but lot's of unburnt fuel coming out of the pipe. I have yet to see this addressed my LHS guy told me to watch for this. And sure enough when the tank started to get low the blue smoke increased. So... I leaned her up a little and all is well so far... But tomorrow will be a different day. I live in Georgia and the weather can make yesterdays settings useless. Which does get agravating I admit!
I don't have a temp meter so I use the spit on the head method, read the glow plugs, listen to what she's telling me, and watch the blue smoke. I 've found when you've hit the sweet spot she'll tell ya, if you know what I mean! I am going to try a different plug other then McCoy, that is all my LHS offered me.
Speaking of reading glow plugs, Ron Paris has a great advice in this area. However, it is a shame there are no pictures. I even asked OS about this and they said, sorry what we have on the web is the best we can do. Look up any spark plug reading material and there will generally be pictures associated with it.
One last thing and probably most important to me is this is a race engine! No less then any other Alcohol burnin, top fuel dragster! Traxxas may say RTR but IMO that is kinda of a tounge in cheek expression.
I have enjoyed reading your posts and have learned as well. I look forward to chatting with you in the future as I'm sure I'll run across that strange thing goin' on that I can't figure out as well.
Last edited by redpwr; 05-29-2007 at 09:35 PM.
OK, I think I have it running now, I can keep topping the tank up from about 1/3rd full and keep it running. (I found some metal particles and rubber 'worms' when I removed the HSN).
It now is definitely running well into the rich side though, and I am scared to lean it any more in case it starts overheating again.
It take ages to warm up now before I can get second gear, how long does it normally take to warm up this engine with normal conditions?
If I keep it running it's ok, but it bogs if left to idle for more than a few seconds. Once left to cool down, It takes a long time again to warm up (a good few minutes).
I actually watched the dvd that came with my new t-maxx. I ran the 5th tank through as shown on the dvd. I called my hobbie shop guy, and he informed ms that I should run a gallon to break in the motor. I am having a hard time getting the motor to shift into second, thats when he told me to hold on before I go balls out!!Originally Posted by JoulesWinfield
1 gallon! No the motor breaks in way before that, but you don't get optimal performance till 1 gallon. There's a sticky in the FAQ section to assist with the Traxxas tuning method. Check it out, it has some excellent tips on tuning to kind of help clear things up.
Founder of H.U.A.
I spent What??
I had a promblem with tmaxx. It starts out great, but then it dies out. any suggections
does any body know the best needle settings please help me?
whts the difference of getting a tempature reading from the glow plug instead of from the outside of the head
it wont be as hot on the outside of the head. so you will get false readings.
Those who throw dirt are bound to lose ground.
The link does not work.
You have to find that for yourself. Read the manual (!!) supplied with the truck, and follow the instructions on how to achieve the correct mixture for your engine. Be patient!! It takes a lot of experimentation and effort to truly understand how your engine will respond to different settings. If I want to make an adjustment on my engine, I don't even have to think anymore on what to do. Like learning to ride a bike... AND: Because of temperature, humidity, and altitude differences, each engine will be happy on it's own unique settings --> that is why YOU have to tune your engine. The sooner you start to put effort into learning how your truck works, the sooner you will begin to enjoy it!! Good luck, and rememeber to read the manual. Don't overlook the basics like a using clean air filter, fresh fuel, and a good plug.Originally Posted by Traxxas King
Revo 2.5 that pops wheelies like nothing!
Carb issue: Been there done that... On the REVO, there are two holes in the engine base where the throttle bellcrank locates. Use the hole closest to the carb (nearest to engine). You can also adjust the angle of the horn on the carb slide where it fits into the bellcrank slot. Loosen the grub screw on the side of the horn and operate the throttle by hand. Adjust the angle until you get a smooth motion from the mechanism.Originally Posted by redpwr
Glow plug in TRX 2.5: Use the genuine Traxxas plug or alternatively a NovaRossi #5
Revo 2.5 that pops wheelies like nothing!
"Quit wile you're ahead" - put the truck away before it diesOriginally Posted by tmaxx25101
Be a bit more specific. Does it start easy? How long does it run before the trouble starts? Will it rev cleanly and change up wile it is still good?
Revo 2.5 that pops wheelies like nothing!
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 your HSN, you have to richen your LSN...this is because when you lean out the HSN it restricts the flow of fuel to the LSN, hence you have to richen the LSN to maintain a proper air/fuel mixture & reliable idle...and same applies when when you richen your HSN, but (opposite direction) you lean out 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 (<-- Click!) when your tune is way off and start re-tuning from there...in the following links there is "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...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 (<-- click!) works very well)...and DO NOT tune for a specific temp...ONLY use the temp gauge to make sure you stay UNDER 270 degrees...(Click! -->) Tuning Guide #1, Tuning Guide #2 & Tuning Guide #3 (<-- Click!)...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 (<-- click!) with illustrations...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...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...***
full sized image can be found here (<-- click!)...
***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 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"
Maybe you should email Traxxas itself. I know them to be nice and sympathetic on trouble like this. Good luck and better rides!
how bought a "how to tune your 3.3
because it is tuned exactly the same way as the 2.5 and 2.5R...Originally Posted by REVOGOD33
"Growing OLD is mandatory, Growing UP is optional"
if its running to rich your engine wont have enough umph to engage the syntripical clutch that shifts it into the second gear.thats what mine does anyway. hope it helpsOriginally Posted by tinmannj
I have a Go Tech R21 engine and would like to know if it would work on my original T Maxx .15????? email me at firstname.lastname@example.org
Ive got the trx 3.3 and have to say it was the easiest thing to tune. I didn't have any problems with break in, and it just stayed running no matter what i did to it. No complaints on this side for sure with the 3.3. The 2.5r i had works excellent well no issues what so ever. I live in upstate NY where it usually stays right around 80 with 60 percent humidity al the time in the summer so day to day running is very simple.
Read the link I provided and all links within it. If you have further problems you can PM me or contact Traxxas Support, they are acturally one of the best support groups I have ever dealt with.Originally Posted by tmaxx25101
The tuning is not different. Read that sticky and it will give you a couple of tips and tricks as well, like tuning with 1/2 a tank.Originally Posted by REVOGODD33
There are only the factory settings to get you started, there are too many variables to be able to specify how many turns out your needles need to be. If you read your book you would know that Temperature, Altitude, Humidity, the type of fuel and nitro%, your exhaust and air filter types all affect what your needle settings would be at.. On top of that no 2 engines are 100% identicle.Originally Posted by Traxxas King
Follow the sticky I posted and all the links, if that does not work then contact support because you may be having some other issue affecting your tune...
It is the area of the glow plug that is most steady in it's temps, as the wind flows through the wind they cool and dissapate the heat from the motor like a radiator. But the position of the glowplug is consistant in temps and that's why all mfr's refer to glow plug area temps in their manuals....Originally Posted by Traxxas King
Founder of H.U.A.
I spent What??
Links dont work!!!!!!!!!!!!!!!!!!!!!!!!!
Newbie needs help!!! The links to aforementioned article don't work with the new website this is my first nitro adventure. I have a first gen T-Maxx with the original .15. I just need help with tuning. Sluggish off the line, amazing middle, then falls on its face. Lookin for some help ! Lol
Links still no workee...
I am buying a traxxas 4 tech 3.3 from Dubai and i live in Pakistan and i dont think i will be able to get Traxxas top fuel 20% here.
so can you guyes please suggest what kind of fuel can i use. i think i can get fuel used in thunder cat RC cars from here. is there any way i can use the formula and make it myself.?
hy,i am from austria,i need help.i need the part number from the ofna 26 carb.this carb is from ofna Flash 26,it is for my jato 3,3.Thanks
Those 2 links do not work
i once thought i knew it all about tuning engines, with 30 years automotive, motorcycle/snowmobile and small engine tuning experience, i found myself troubled with tuning these little nitro burners. it was not until i really took the time to understand the carb and how it differs from that on a weed eater was i able to get a fine tune on my 3.3. The carbs on nitro engines are called a "simple" carb, there is only one fuel circuit and no air bleeds. a rule of thumb, on a simple carb, the faster the air flows through it, the more fuel it discharges. The High speed needle regulates the amount of fuel coming from the fuel line to the discharge nozzle, the low speed needle regulates the amount for fuel allowed out of the discharge nozzle when the throttle is closed to 1/4 open, after that it has no effect. The reason there is a low speed needle, is that since there is no air bleed, the high amount of engine vacuum at idle would try to suck as much fuel into the engine as the HSN would allow, so the LSN limits the area of the discharge nozzle thus leaning the mixture. So after all of this learning, and reading my manual over and over again, this is what i learned. At 2700 feet elevation 85 deg day 15% humidity, 4 turns HSN and 1.75 turns LSN are a great start for break-in, i had to lean the LSN 1/8 turn to get it to even move at !/4 throttle, it still ran like crap, but i left it set like that . Once broken in, the manual gives no specific needle settings, but to fine tune the engine for best performance. Once i was able to make some short full throttle runs after 7 tanks of fuel, i was able to dial the HSN to 3.5 turns to achieve a nice clean exhaust note, good throttle response above 1/2 throttle with enough smoke. I then started to work on the idle and low speed circuit using automotive knowledge, and the pinch test to verify the results. I set the throttle stop to 1.0mm, Then with the engine running,very slowly started to lean the lsn 1/16 turn at a time and waiting about 10 seconds between turns for the idle to stabilize. after about 1/4 turn in i had to lower the throttle stop because the clutch was wanting to engage.I continued leaning and counting to ten until the engine died from fuel starvation. I then enriched the lsn 1/8 turn and restarted the engine, and then fairly quickly richened the lsn until it just started to run rough. I called this point the rich limit, and the point where it died, the lean limit, there was only about 1/4 turn between both limits. I found the point right between both the limits gave me a 3 second run time using the pinch test. This setting ended up being 1.4 turns out on the LSN on my car in this weather. I feel the pinch test is the best way to set idle mixture, but i feel that by finding the limits allow me to quickly find the needle settings to achieve good pinch test results. If i have to open my LSN much to regain idle quality, i replace the glow plug and look for air leaks. Air leaks affect idle most since crankcase vacuum is high, and as the vacuum drops to near 0 at WOT it makes leaks less obvious. This is my 2 cents.
The article has been moved anyone know where i can find it thanks
This is the second time i have tried to read that article but when i click the link it tells me it no longer exhist, I would love to read it, if anyone has it please email it to me thanks email@example.com
This thread is really outdated, for tuning advice either read your the trx 3.3/2.5 manual or check out these websites:
Intro to nitro engines
General tuning guide
This is how to read a glow plug
Tuning chart posted previously
Also check out post #101, it contains some good info.
Hope a mod sees this and will update the first post of this thread.
Last edited by maxidodies; 01-24-2012 at 04:44 PM.