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carb question....

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icunvmytmaxx

icunvmytmaxx

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Ok Ok....here's the deal. This should be an easy fix but I can't figure it out..I just put a new 2.5r engine in my Tmaxx. Broke it in right to traxxas specs. When I hit my brakes, the barrel closes till the 1mm gap. Now, my question is....when I shut my truck off, I've got a pretty good gap, (more than 1mm). If I take my finger and push the barrel in, by the lsn, it kind of springs back out. And opens the gap back up. When I hit the throttle, it opens all the way but only comes back to about halfway. Give or take a little. What's going on here? To my understanding, when the throttle servo returns to neutral, the gap should go back to 1mm. Any thoughts or suggestions would be great....thanx in advance.....Kev
 
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To me, it sounds like you have a servo saver on the Throttle/Brake Servo, and it isn't allowing the Engine to close all the way back to the 1mm setting. The spring on the servo saver is pulling the engine open. Past the 1mm gap and when you hit the brake the servo saver is springing the other way which is pushing the carb closed. releasing the brakes releases the extra tension and it opens back up....
 
mjneid said:
To me, it sounds like you have a servo saver on the Throttle/Brake Servo, and it isn't allowing the Engine to close all the way back to the 1mm setting. The spring on the servo saver is pulling the engine open. Past the 1mm gap and when you hit the brake the servo saver is springing the other way which is pushing the carb closed. releasing the brakes releases the extra tension and it opens back up....
Click to expand...
ok......so is this normal? I mean, it just don't look right to me. My idle seems ok but i do have a little bit of the "creeping forward" thing going on at idle. I also saw in another post something about adjusting the throttle return spring on the rod? Something about keeping a little bit of a load on it so the carb returns back to the 1mm gap. I really don't see this as being a bi deal but is like to try and get rid of the creeping forward if I can. I've only adjusted my hsn. Getting great smoke. I haven't touched my lsn yet. Thanx again.
 
What radio do you have? Your new carb may not be at the same angle as your old one exactly and adjusting the EPA on your radio should get it done. With the radio at "neutral", the carb barrel should be resting on the idle set screw. You should not be able to push it in at all.

Either linkage or EPA's need adjusted or both.
 
Yeah, it's probably the linkage. Every time you drop a new engine in your truck you should always adjust your linkage. It just takes a few minutes and it will save you headaches later on.



:Washington_National:redbuggy:
 
cwal1774 said:
My money's on the linkage, pop it off and shorten it a couple turns.
Click to expand...
now when you say linkage, which part do I take off? I've got the small rod with the cup on it that goes from the end of the barrel to the bell-crank. Then ya got the long one that goes from the bellcrank to the servo. I'm thinking you mean the short one with the cup on it. Take this off and shorten it so it pulls the barrel closed?? Thanx again for the help, all your responses are appreciated. Bear with me now.....I'm still new at this. Learning everyday.
 
I would pull the linkage off at the carb and check where your idle gap really is. Adjust it as necessary to get it to 1 mm.
Take off the throttle servo horn and turn on your radio and zero the steering trim. Then put the servo horn back on. Then put the linkage at the carb back on and adjust the length as necessary so it doesn't pull the carb open at idle. That should fix any linkage issues.
It sounds like your linkage is off and opening the carb up too far at idle. Your linkage shouldn't close to 1 mm when your brake. It should close to 1 mm after you release the throttle. That might explain the creeping forward issue you're having. Idling high enough to engage the clutch.
Hope that helps.
 
You may even get away with turning your trim back a little. With the radio and rx on, squeeze the trigger slowly all the way and see if the servo is still trying to open the carb after it's all the way open. If it is, you should be able to trim back. Then adjust the brake linkage to operate correctly.
 
After messing with this. I'm still seeing a problem. It may be so stupid, I'm looking past it but. I took my engine off and played with the idle screw a little bit. When I hit the throttle, it returns to this spot in the pic. After braking it returns to this same spot. Why is it doing this? It just seems like I can't get it to stay at the 1mm gap. It keeps "springing" (so to speak), back to this spot. Any help would be great. Thanx again.......Kev.
e488392f.gif
 
Maybe I am missing it in the pic but I don't see a throttle return spring. That may be part of your problem there.



:Washington_National:redbuggy:
 
Riz23 said:
Maybe I am missing it in the pic but I don't see a throttle return spring. That may be part of your problem there.



:Washington_National:redbuggy:
Click to expand...
yea man, I took my engine off. I still can't figure this out. Anybody got any ideas? Pretty sure I've tried just about everything.
 
cwal1774 said:
Have you tried loosening the pinch bolt and turning the carb?
Click to expand...
I took my idle screw all the way out, turned the carb, replaced the screw. It just seems like when I push the barrel all the way closed, it pops back to this position. Where's the pinch bolt? Not too sure about any springs. I'm worried if I rip this thing apart any further, I'm gonna screw something up. I might learn something though. Thanx for all your help.
 
The linkage keeps it closed when it's assembled. It's normal for the boot to hold the barrel open a little bit. That's why it's a good idea to have a return spring directly on the carb; not just the linkage. If it's not closing all the way when assembled, the linkage needs to be adjusted.
 
Is it normal for it to do this with my engine right out of the truck? I mean, I have the motor in my hand, with nothing hooked to it, and it still has the spring action thing going on. I'm not understanding this at all. Must be Soooooo stupid. Cause its the easy things I don't get. It just seems to be forcing its way back to this position. Doesn't seem right to me.
 

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