Results 1 to 3 of 3
  1. #1
    RC poster
    Join Date
    Nov 2003
    Location
    Cumming, Ga
    Posts
    15

    Truck jerking when starting from a dead stop - normal?

    A few days ago I drove my Tmaxx for the first time.

    When ever its stopped and I start to drive forward it jerks really bad a couple of times until the truck gets moving. Is it just the clutch breaking in?

    Also I put the truck in reverse and now it's not going back into forward gear. What am I doing wrong?

  2. #2
    RC Qualifier
    Join Date
    Aug 2002
    Location
    Colorado Spirngs CO.
    Posts
    944
    It is normal in that EVERYONE has this problem at first, but this can be fixed. Your engine rpm at idle is to high. Because the engine can't stop turning when the truck stops, and because of the reverse mechanism, power had to be stoped inside the tranny. An internal clutch will engage at a certain rpm to drive the truck. An idle rpm that is too high will cause the clutch to grab, but when it dose, the extra load slows the rpm and the clutch lets go. I have had mine just sit there and shake because if it. I would look first at you idle stop screw located on the carb. The opening in the carb should be 1.5-2 mm when at idle. If you have this adjusted properly, then it is engine tuning. The fast idle will also cause the truck to get stuck in foward or reverse because there is an other clutch that prevents the truck from being shifted into the opposite direction while in motion. Make sure to break-in the engine properly, or if you have already, then make sure to warm up the engine before tuning.

    Put the trigger to the plastic!

  3. #3
    RC Qualifier
    Join Date
    Aug 2002
    Location
    Colorado Spirngs CO.
    Posts
    944
    So, after you have broken in the engine, if you have not yet finished break in, don't bother with the jerking and shifting untill you do. The engine is not running at performance levels during break in, so don't expect it to.

    After break in, the way to fix the problem if it dose not fix itself is this: The jerking under acceleration is mainly caused by a rich fuel mixture. This will cause the engine to have very poor power output when starting from a stop. Because of this, when the tranny clutch grabs, the engine rpm drops because the engine dose not have the power and the clutch lets go. This can occur serveral times in a row before the engine either blows all the excess fuel out, or gains more rpm. Make sure your low speed needle is flush with the arm housing. This screw, once adjusted, should not realy need to be messed with anymore.

    So, after you bring the engine up to operating temp, and you find it needs tuning, proceed to observe how the engine responds to figure out what you need to do.


    Let the truck idle for 5 seconds, then gun it. If the idle speed drops, causing the need to blip the throttle to keep the engine running, or after the 5 seconds, when you hit the throttle and it bogs down right off the bat for a moment. You need to lean the mixture.

    If the truck takes off after the 5 ok, but seems to cut out once the truck has gotten some speed, the mixture needs to be richened.

    Note the engine should still be putting out that blue tint smoke, particulary under acceleration, and should not become hotter than the engine max operating temp. (depending on engine)
    Put the trigger to the plastic!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •