Traxxas T Maxx 2.5 Idle Issue

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mg444

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Hello -

First off, I'm very new to nitro and the Traxxas T Maxx 2.5 is my first nitro truck. I have many electric RC's. Anyways, I have a brand new T Maxx 2.5 and I have the engine broke in. The problem is the idle speed, it's super super high and I can't adjust it down. I've been doing research on this forum and I know of at least one post about this but I don't know what the definitive solution was. With the engine off the ground, it will idle so high that it will almost hit 2nd gear. I *believe* I have a throttle linkage issue. I've adjusted the idle screw, doesn't help. Tried adjusting the low speed needle, no luck. I have the high speed needle set good, just a little rich but not to much. I don't know how to adjust the linkage though. If someone could help I would appreciate it. Links, pictures, explanations would all be helpful. Thank you.
 

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Hello -

First off, I'm very new to nitro and the Traxxas T Maxx 2.5 is my first nitro truck. I have many electric RC's. Anyways, I have a brand new T Maxx 2.5 and I have the engine broke in. The problem is the idle speed, it's super super high and I can't adjust it down. I've been doing research on this forum and I know of at least one post about this but I don't know what the definitive solution was. With the engine off the ground, it will idle so high that it will almost hit 2nd gear. I *believe* I have a throttle linkage issue. I've adjusted the idle screw, doesn't help. Tried adjusting the low speed needle, no luck. I have the high speed needle set good, just a little rich but not to much. I don't know how to adjust the linkage though. If someone could help I would appreciate it. Links, pictures, explanations would all be helpful. Thank you.
Welcome bud.. well definitely sounds like the linkage is set up wrong or off. Or it could be the tuneing. Since you have messed with your niddles. I would reset the carb to factory settings and start over. Unfortunately.. question what fuel are you running?? That could also be your issue if you say what I think your going to say..here are some links for tuning and reseting the 2.5 carb. I got the 2.5 and recently built the 3.3.. I love them but got to get past the set up.. its frustrating for sure I know your pain😉🤣👍👍
 

mg444

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Thank you for the reply Stoner RC. I'm using Traxxas Top Fuel 20% nitro. I know how to reset the carb to factory settings so I'll do that. What bothers me is the idle adjustment screw does nothing to help. I read someplace about adjusting that "gap" in the carb, is that adjusted by adjusting the throttle linkage? Yes, this is frustrating, but I'm not giving up. I like to tinker on it so I want to fix this myself. Local hobby shop wants $60/hr to tune. They estimated between 30-45 minutes to do this. I really don't want to pay that. I was hoping for some advise over the phone when I called - no luck.
My local hobby shop also said for every degree under 40 for outside air temperature the engine has to be re-tuned.... Is that true? If that is true, I'm going to be doing more tuning than driving.
 
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mg444

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I have it running pretty darn good! I reset the carb, took it out to run, and starting tweaking. The main problem was the low speed adjustment screw - way messed up.

I even got the truck to go in reverse! That's something we could never get to work.

Thanks all.
 

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I have it running pretty darn good! I reset the carb, took it out to run, and starting tweaking. The main problem was the low speed adjustment screw - way messed up.

I even got the truck to go in reverse! That's something we could never get to work.

Thanks all.
I kinda figured you were going to say TOP FUEL... now that you got the engine broken in.. get away from the top fuel.. O'DONNELL, VP,
Bones Brew.. Top fuel has way to much oil in it. That's why you have problems with tuning.. its upper 14% oil.. you want fuel with around
9-10% oil..That's awesome glad to hear you got it running.. yeah I personally don't run my nitro's once it goes below 50° any more.. a little trick for you while running in the cold.. put a piece of tin foil around your cooling head. It will help keep the Engine warm. What I used to do back when I ran them in the cold..helps keep the head warm and not allow it to get to cold.. Also use a hot plug.. just watch your temps. Don't want to over heat the engine.. just watch useing the reverse sometimes the servo doesn't push the rod back into the trans.. and it acts like it's broken or stripped it's gears. I personally took that servo out after a handful of runs. When I first got my 2.5 back in 99 2000.. I have had the truck a long time. It's a good truck
 

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