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  1. #81
    RC Racer
    Join Date
    Oct 2006
    Location
    Middletown, Pa
    Posts
    232
    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.

  2. #82
    RC Racer
    Join Date
    Nov 2006
    Location
    Johannesburg-WestRand
    Posts
    110
    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"

  3. #83
    RC Racer
    Join Date
    Jan 2007
    Location
    Dudley, NC
    Posts
    204
    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.

  4. #84
    RC poster
    Join Date
    Mar 2007
    Location
    Boston northwest
    Posts
    1

    New to R/C 2.5

    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?
    HELP
    Regards,
    2.5 new Horst

  5. #85
    Traxxas Employee Nitro Chicken's Avatar
    Join Date
    Jan 2001
    Location
    Chicken coop
    Posts
    6,245
    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!"
    Foghorn Leghorn

  6. #86
    RC poster
    Join Date
    May 2007
    Location
    Massachusetts
    Posts
    7

    Stalling issues

    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.

  7. #87
    RC Competitor
    Join Date
    Sep 2003
    Location
    South Central,Los Angeles
    Posts
    62
    how fast would would the 2.5 engine go if you got it ported?
    R.I.P Eric(Eazy-E)Wright 1963-1995

  8. #88
    RC poster
    Join Date
    May 2007
    Location
    West Yorkshire, UK
    Posts
    5
    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 >>>

    http://www.tmaxx.free.fr/docs_25/TRX...%20Traxxas.pdf

    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,
    Thanks.

  9. #89
    RC poster
    Join Date
    May 2007
    Posts
    11
    Hello all,
    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.

    Later,
    Last edited by redpwr; 05-29-2007 at 09:35 PM.

  10. #90
    RC poster
    Join Date
    May 2007
    Location
    West Yorkshire, UK
    Posts
    5
    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).

  11. #91
    RC poster
    Join Date
    Jul 2007
    Location
    new jersey
    Posts
    10

    breakin time w/2.5

    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!!
    Quote Originally Posted by JoulesWinfield
    @smg323, Im not denying that my lack of nitro experience could be the reason the first engine was such a pain.

    Like I said, the first gallon was a blast. The thing seemed to run like mad.

    Im hopeing that this new 2.5R will be better, and renew my confidence in TRX enginges, cause I really want to trade this one in for the TRX3.3.