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Carb question?

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c0mf0rt

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While I'm waiting to get ahold of traxxas about my new TMAXX issues. I've traded a guy for a used one with a 3.3. I got it to start but the thing goes almost immediately to what has to be max rpms. I adjusted the hsn very rich to where it was just pouring out of the exahust but the thing keeps revving. I also noticed after trading the guy for it that the spur gear is totally stripped.

Any ideas? Vacuum leak? Carb set incorrrectly?
 
Yea def check your gap at idle also where's the lsn at? Hsn is only for when the throttle's hlaf way or more open if its idleing it would b idle adjustment and lsn u wanna look at. Also check your trims on your remote I've seen people have them cranked up before.
 
K thanks guys.... I'll have a look.... so definitely sounds like a carb issue though right... not a motor problem?
 
Yup. Might have an airleak causin it to run lean, search here and you'll find links on how to check for one, but my guess would b carb or trim/throttle linkage issues.
 
I've moved hsn, lsn, and idle screw all over the place and that sucker still goes immediately to "I'm going to friggin explode" rpm once started. Another problem.... probably unrelated but it's pretty hard to get the gas flowin in this sucker.... somewhat difficult to prime... plus the gas line to the carb is short... last guy must have cut it.
 
I would pull that motor and check for air leaks. Grab some soap and water and brush it around the head, backplate, and carb where it seats, then blow into the carb thru a piece of clean fuel tubing with ur finger over the carb and exhaust opening. I would also so the same for the gas tank. If you have a leak it won't generate the pressure it needs to feed fuel in properly and the engine will run hot and lean. (Lean equals more air than fuel essentially) Also blow hard as the tank should hold 6-7psi if I'm not mistaken, tho it could be more or less I'm goin off memory lol. The fuel feed line on these also is normally short, they leave it at the minimum necessary it seems like, which sucks because they flip n shut off 5 seconds later. I personally added a few inches to mine as well as a fuel filter.
Another thing is if you need it factory settings should be 1.5 to 1.75 out on lsn from fully screwed in, and hsn should be 4 turns out from closed. I would set em there then tune from there. Did you get the spur gear replaced so the clutch bell can't free spin?
 
Thanks for the help... I'll give it a shot... I haven't messed with the spur gear yet because I wanted to get the motor straight first. I don't want it revving up and hauling ace or ripping the new gear to pieces.... catch 22 though huh? Not supposed to run it without a load.... hmmmmm
 
So I read up on the "tuning tips" thing.... the spot where I'm supposed to have a 1mm gap is definitely larger on this TMaxx as compared to my brand new one. But the needles don't seem to be changing it. Which needle should adjust that small gap?
 
Make sure ur throttle isn't holdin it open. Cut the trims all the way back to brake and make sure the linkage isn't stuck on anything. Then the screw is at the base of the hsn, lookin at the truck from the back its on the right side. Should be a silver flat head screw, and I believe clockwise closes the gap but dbl check that on traxxas' site.
 
I'll check it... are you saying the idle screw closes the gap? As far as the trim, I actually disconnected the linkage just to make sure that wasn't my problem.
 
Yes, idle screw will close the gap if you turn it CCW. You may have to gently press on the carb slide where the linkage connects to get it to go in as you screw out the idle adjustment screw.
 
FOUND THE PROBLEM..... I went ahead and decided to seal the whole engine since it was used and I didn't know how old etc. Anyway, right at the end I noticed the carb "housing" was cracked around the base of where the HSN goes in... bingo.... rtv'd it for now but will be ordering a new one. Thanks for the help!
 

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