2.5 In S-Maxx. Idle fluctuates and doesnt hold tune! HELP  
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2.5 In S-Maxx. Idle fluctuates and doesnt hold tune! HELP - 8/17/2005 12:41:55 PM   
zr1s10



Posts: 372
Joined: 5/1/2005
From: Fort Huachuca, AZ, USA
Status: offline 		Ok my buddies got a S-maxx and I'm somewhat baffled myself. He filled the tank up after warming it up. We got it tuend great, plenty of smoke and it has lots of power. But the idle fluctuates and after running for a while the tune kind changes.

Now I told him he probably has a air leak, BUT the truck is still almost new?!?!!? He's never messed with the carb (never removed it) or the backplate. I think he's got a little over a half gallon thru it.

Ideas???

_____________________________

T-maxx: Picco P2, XR2i, & much more
9.5 MBX: Proline truggy adaptors, Proline 23mm Wabash's, Proline 40s Dirt Hawgs, & XR3i!
Hyper 7 PRO: Picco 27 OUTLAW, Nova Race PRO Head, graphite goodies, Futaba S9350's, JP-2, Crimefighters, & Spektrum DX3 2.4gh
       Post #: 1

RE: 2.5 In S-Maxx. Idle fluctuates and doesnt hold tun... - 8/17/2005 1:15:06 PM   
proxpilot


 

Posts: 989
Joined: 10/13/2004
From: High Point, NC, USA
Status: offline 		check the gas tank gasket make sure it's not messed up, and if there are two little screws on the under side of the tank lid tighten them down, also check and see if the high speed needle is tight

(in reply to zr1s10)
       Post #: 2

RE: 2.5 In S-Maxx. Idle fluctuates and doesnt hold tu... - 8/17/2005 1:41:30 PM   
zr1s10



Posts: 372
Joined: 5/1/2005
From: Fort Huachuca, AZ, USA
Status: offline 		When you say high speed needle you mean that collar around it?

_____________________________

T-maxx: Picco P2, XR2i, & much more
9.5 MBX: Proline truggy adaptors, Proline 23mm Wabash's, Proline 40s Dirt Hawgs, & XR3i!
Hyper 7 PRO: Picco 27 OUTLAW, Nova Race PRO Head, graphite goodies, Futaba S9350's, JP-2, Crimefighters, & Spektrum DX3 2.4gh

(in reply to proxpilot)
       Post #: 3

RE: 2.5 In S-Maxx. Idle fluctuates and doesnt hold tu... - 8/17/2005 1:52:01 PM   
maxximum_overdrive


 

Posts: 510
Joined: 3/16/2005
From: little rock, AR, USA
Status: offline 		the tuning issue is prob. do to the infamous max fuel tank. it has a design flaw. it is to tall. when it is full it will cause the carb to let more fuel though, making the truck run rich. so when you tune it out at full tank, by the time you get to half tank you are lean and starting to over heat. by the time you are almost empty you are starting to really overheat and lose power. on the other hand if you tune when it is almost empty, it will be so rich at full tank that it will hardly run. the solution...................get a rustler tank, or tune at half tank, so you will be slightly rich at full tank and slightly lean near the end but not so much that you will cause the engine harm.


your idle issue does sound like an air leak.........to check for a leak spray some staring fluid (ether) around the base of the carb and around the back plate while it is running. if it is sucking air the engine will accelerate. if theres not an air leak it will clean your engine off a little . anyway the 2.5 is a tricky engine that once tuned properly will really impress you for its size. good luck and if you don't get it worked out you can always tell your friend ot upgrade to an os .18 tm. it drops in and will greatly improve drivability/tunability. peace

(in reply to proxpilot)
       Post #: 4

RE: 2.5 In S-Maxx. Idle fluctuates and doesnt hold tu... - 8/18/2005 8:59:02 AM   
Dil



Posts: 518
Joined: 10/27/2004
From: Colombo, SRI LANKA
Status: offline 		well i know this kind of thing very well i had the same problem with my brand new t-maxx, idle goes up and down tune settings never stay, engine stalls, well here's when i figured it out, check out the two silver nuts in your carb in front of your high speed needle and on the side of it, get a hex wrench and remove the nut and check the nut thread in the carb, in mine the thread was all in pieces when i removed the nuts, (in both) , and the nuts could be just put in and taken out i mean the thread was totally gone , in a problem like this the carb will have to be replaced i preseume this might be your problem, but sometimes when u remove it the threads might seem to be in place therefore try tighting it and before removing it, if it does not tighting(the nut will just keep turning and not tighting) it will confirm your problem or if its not that u have water in yor fuel!(your fuel is contaminated)

_____________________________

I Could'nt Fix Your Breakes, So i hooked up a loud Horn

(in reply to maxximum_overdrive)
       Post #: 5

RE: 2.5 In S-Maxx. Idle fluctuates and doesnt hold tu... - 8/18/2005 1:05:47 PM   
zr1s10



Posts: 372
Joined: 5/1/2005
From: Fort Huachuca, AZ, USA
Status: offline 		Well I highly doubt theres water in his fuel considering its brand new and it would be a manufacturing issue. But like said earlier I really think it's the tank pressure thats causing the tuning issues. Still dunno bout the idle?

_____________________________

T-maxx: Picco P2, XR2i, & much more
9.5 MBX: Proline truggy adaptors, Proline 23mm Wabash's, Proline 40s Dirt Hawgs, & XR3i!
Hyper 7 PRO: Picco 27 OUTLAW, Nova Race PRO Head, graphite goodies, Futaba S9350's, JP-2, Crimefighters, & Spektrum DX3 2.4gh

(in reply to Dil)
       Post #: 6

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All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> RC Monster Trucks >> Traxxas Monster Truck forum >> 2.5 In S-Maxx. Idle fluctuates and doesnt hold tune! HELP
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