Engine pulsing?

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vpalace

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In advance, I apologize if this has already been discussed, I could not find an answer when I searched.


I finally got my XTs fuel line straightened out. Radio in, new 7.2v battery, needles reset and new carb/manifold gasket.


Started it with 1 pull, HS needle is set pretty good, revs up good and is fast! I think I had the LS needle set, but at idle, the engine kind of pulses or surges, meaning The rpms go up and down. Adjusting the idle does nothing. If I richen the LS up, it bogs and wants to die, leaning it out and the engine revs real high. I got it to to a point where it takes off great and winds out awesome. Just this little problem.


It was suggested that it could be an air leak, which I was told how to check. Is there possible anything else that I am missing?


Thank you.
 
If you adjust the idle and it does nothing does your servo allow the idle arm to rest on the idle screw? With you car at idle the idle arm should rest on the idle screw if the servo is pulling the arm forward then adjusting the idle will have no effect.
 
might wanna try new gas too. i put brand new premium gas in my atv & it pulsed & sputtered. i cyphoned the gas & replaced it & it ran perfect. hard to diagnose your problem w/out being there but a possibility.
 
sounds like an air leak. Without opening the carb while it's running see if you can wiggle the throttle shaft front to back without rotating it or if it will slide in or out of carb, could be worn.. Or could be a slight gasket leak....
 
Ok, so I got to take it out today, checked for leaks, none, no slack in the throttle linkage either. So I decided to just start over and retune. After loosening up where the throttle linkage connects to the servo horn (it was sticking and when ever you let go of the brakes, it would take off) everything seems to be in tune!

It revs a little bit high at idle, which I like. Is this ok? And full throttle it screams! No, I did not check the plug so I'm not sure if I'm running it too lean yet. I was just happy to have it running and working good! I will do the plug test when I take it out this weekend.

On another note, I thought my carb was bad, and redcat sent me a new one. Ain't broke don't fix it? Thinking I should just throw the spare in the toolbox and leave things be. Good idea?

BTW, with everything stock, except for the new 7.2 battery, servos and dt1 filter with velocity stack, what is the typical top speed of the xt?

I want to thank everyone for their input and patience with me as I was getting this up and running, I know I was a pain in the ass and I appreciate all the help.
 
If your idle is sporadic, you may want to check your choke. The choke lever wiggling around and sporadically richening/leaning your mixture will cause a strange idle. This happened to me when I first got my XB, during the break-in. The choke lever never "clicked" into the proper position because the fuel line was holding it back, and I never noticed.
 
Funny you mentioned that, as I think that was the issue all along. I changed the choke lever and never seated it fully and when I opened it, it wasn't fully opened, just a small small bit closed. Didn't think it would be that temperamental.
 
Lol, not running anymore! Read my other thread in the electronics section. Haha. I fried somethings.
 
I'm not sure. It's been like that for a bit. I think the wires may have gotten chaffed that go into the box and they touched.
 
hey that's possible. i had to cut a lil more plastic off with the servo wires, the killer bee & the voltwatch. what's crazy is that you said your rx was still fine.
 
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