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  1. #1
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    Is the spur gear supposed to spin while truck is not moving?

    I have a black tmaxx 2.5 that I put a 3.3 into. Is the spur supposed to be spinning when the truck is not moving? Or is this a sign of a bad carb setting?

  2. #2
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    Sometimes the spur will freewheel or “windmill” a little from the vibrations of the idling. If it is spinning so fast that the clutch is engaging and the truck is moving the. Your idle is a little too fast .

  3. #3
    Marshal Double G's Avatar
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    The idle should be low enough so that the clutch does not engage the bell. If you have a two-speed tranny then there is a second clutch inside as well. It could also be the clutch is fine but the friction in the bearings causes the bell to spin as well.
    The Super Derecho

  4. #4
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    If you have reverse still installed the spur gear can spin without the truck moving. The transmission has extra gears in it. Nothing to worry about. But, if your idle is too fast it will act like it's "bucking" or "jerking" trying to get the truck to move.

    If you do not have reverse in your transmission the spur gear wouldn't be able to turn without the truck moving.

  5. #5
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    Here's a video of what I'm talking about:https://www.youtube.com/watch?v=pEGj...youtu.be&t=119
    At the 2:18 mark you can see truck "bucking/jerking"
    At the 3:33 mark you can see the spur turning and truck not moving.

    Thanks to Double G for finding and posting(in a nitro slash thread) the old Traxxas video.
    I don't know how to copy youtube address with a set time on video.
    Last edited by grizzly03; 09-29-2019 at 02:16 PM.

  6. #6
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    Hey guys thanks for the replies. When I put my 3.3 in, I just reused the fly wheel and the clutch along with the clutch bell. I noticed my clutch was kinda marred and worn but I forgot to buy a new one. I am gonna order a new one this weekend when I have a chance. I noticed my maxx deosnt pop wheelies too much on the street. I’ve seen vids where ppl pop wheelies everywhere. Is this normal? My slipper tight and I have some old chevrons.

  7. #7
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    Quote Originally Posted by Bigboydanny43 View Post
    Hey guys thanks for the replies. When I put my 3.3 in, I just reused the fly wheel and the clutch along with the clutch bell. I noticed my clutch was kinda marred and worn but I forgot to buy a new one. I am gonna order a new one this weekend when I have a chance. I noticed my maxx deosnt pop wheelies too much on the street. I’ve seen vids where ppl pop wheelies everywhere. Is this normal? My slipper tight and I have some old chevrons.
    Well,my T Maxx doesn’t easily pull wheelies on the street either but mine is only a 2.5 and I need to replace the cracked silicone gasket on my header, so the tune is not consistent.

  8. #8
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    Kinda off topic but will the chrome resonator pipe help with power? I am running the crap plastic one. My maxx also rips Gras up so maybe my chevrons slide around too much on the street. I have the old 1st gen chevrons with the smaller rim. I think they’re dry rotted. They have cracks on the inner side wall

  9. #9
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    I can hear my old style chevrons tearing up grass over the noise of the engine, so yea I think they do slip a little on pavement, but grab like the dickens on grass.
    I’m not sure about the pipe. I am pretty new to nitro and have only experienced the stock plastic tubes pipe. From what I can tell, it does it’s job ( as a resonator). I just know I need to replace the silicone coupler gasket on mine.

  10. #10
    Marshal Double G's Avatar
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    "Upgrade" to the resonator and toss the plastic one. Or get a THS.
    The Super Derecho

  11. #11
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    Quote Originally Posted by Double G View Post
    "Upgrade" to the resonator and toss the plastic one. Or get a THS.
    Am I safe to assume that like a bigger gasoline 2 stroke that a new tuned pipe is the best “bang for the buck” upgrade I could do to the 2.5?
    I noticed on one of the “chop shop” hobby suppliers online when I was shopping for the silicone gasket that a whole plastic pipe assembly with gasket and all the mounting hardware was like $2.75 US . Or roughly $1 more than just the Gasket. That alone made me question how good the stock pipe is
    Last edited by Dakratfink; 10-01-2019 at 12:25 PM.

  12. #12
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    Quote Originally Posted by Double G View Post
    "Upgrade" to the resonator and toss the plastic one. Or get a THS.
    Ditch the plastic pipe and get a tuned pipe (Traxxas resonator or THS) Pipes do make a difference in engine power.

  13. #13
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    The plastic one from what I hear is UTTER garbage. When I tune my idle down to the point where the truck stops going forwards on its own a bit and bucking, the engine dies like in 8 seconds if I don’t give it throttel. My truck is also making a wierd noise. It sounds like it is revving while decelerating. Nobody knows what I am talking about...

  14. #14
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    Sounds like an engine tune(too lean?). I have my engines tuned so they can idle longer than a couple of minutes. Make sure exhaust is in good condition. No leaks in silicone coupler.
    As a side note I found that changing to a bigger carb helps with making tuning easier. Less sensitive to needle settings. (ex. 1/8 turn compared to 1/16 turn)

  15. #15
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    Quote Originally Posted by grizzly03 View Post
    Sounds like an engine tune(too lean?). I have my engines tuned so they can idle longer than a couple of minutes. Make sure exhaust is in good condition. No leaks in silicone coupler.
    As a side note I found that changing to a bigger carb helps with making tuning easier. Less sensitive to needle settings. (ex. 1/8 turn compared to 1/16 turn)
    Yeah that’s what I thought but there is hardly any smoke coming out if I lean it any more

  16. #16
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    Could my clutch be sticking to my clutch bell somehow? I think I flipped it when I reinstalled it “for better bite”. I’m tired of th noise the engine makes (it also gets really hot around the cooling head

  17. #17
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    Cool

    Quote Originally Posted by Double G View Post
    "Upgrade" to the resonator and toss the plastic one. Or get a THS.
    You're going to get me into trouble! Lol!

    I really like the look of those

  18. #18
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    I fixed my wheelie issue for the most part. I also flipped the truck in a deep puddle died to the rain in Cali lately. I am running some five year old fuel which I somewhat had a good tune in but I started it today and my idle screw is really far out and the truck is still accelerating on its own while bucking. Is this a carb issue or a fuel thing?

  19. #19
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    Quote Originally Posted by Bigboydanny43 View Post
    I fixed my wheelie issue for the most part. I also flipped the truck in a deep puddle died to the rain in Cali lately. I am running some five year old fuel which I somewhat had a good tune in but I started it today and my idle screw is really far out and the truck is still accelerating on its own while bucking. Is this a carb issue or a fuel thing?
    It sounds like jt is leaning out ,starving of fuel ,if it is ,then it may have a dirty tank filter or it could have a tank pressure
    issue on the fuel tank lid seal ,if your fuel was that old ,chances are ,you have some dried up seals & dirty tank ,carb.!

    Clean the tank ,an check for pressure by blowing into pressure tube ,an holding the carb tube closed ,if you have bleed
    out of pressure out of the tank lid ,then the tank seal is bad ,that will cause a lean out on the engine an rev!

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