tuning/keeping it running/starting problems, please help

[GsElRiMkS]

I have a traxxas sport that I put a 3.3 on it and its very hard to start, but once I do get it started it idle realy high, this is all at traxxas specs for break in and minor tweeked as it is already broke in, and the idle is set at a good gap according to traxxas web site, but wen I hit the breaks it kills even with the carb slide adjusted open more / less or even with fidiling with the lsn and hsn and I'm ready to throw it away or sell it couse its so frustrating, please help

 

[Metalhead Matt]

Make sure everything is sealed. Read the tuning tips and tricks at the top of the nitro forum for sealing details. Check the tank cap, coupler, header and fuel lines for leaks as well. Being that it's hard to start, it sounds like the fuel system is not building pressure properly. I'd seal the engine, make sure the fuel system is sealed and start over.

 

[GsElRiMkS]

Thanks a lot man ill look over that and keep it posted ,

 

[MotoGod]

If your engine is dying when you hit the brakes, you need to adjust your idle screw a bit. Pull your air filter off, turn on your radio. Look down the carb barrel so you can see the carb slide. Now hit the brakes. If the idle gap disappears, then it's set too far out. With the brakes on, adjust your idle screw so that you have @ 1mm of a gap between the end of the carb slide, and the carb body itself.

As far as the idle being high, my guess is your low speed needle is too lean. Richen it up 1-2 hours and see if the idle drops down a bit.

Once you get those things squared away..then go read the tuning guide and try to get a proper tune on the engine. Remember, temp is NOT everything. Listen to the engine, watch the smoke trail, and try and feel the power curve. Temperature is kind of a 4th guideline for tuning a Nitro engine. Don't use it as gospel. The 3.3 likes to run hot more times than not. My Revo would run like crap until I got the engine tune to where it would run @ 280 - 290 degrees. Some of them like to run cooler.....each engine has it's own likes and dislikes ;-)

 

[darkslayor24]

it sounds to me like your throttle linkage isn't set up right. You definitely need to pull the air filter off and set your idle screw with your brakes fully engaged. from there, adjust your throttle linkage so that when you have no throttle input (neutral) so that your carb is closed as much as the idle set will let it. it dousnt sound like an engine issue at all to me, i had the same problem before many times when i switched motors.

 

[GsElRiMkS]

See that's the thing, my idle is set out good and the linkage is good, with the breaks on it does close al the way but dies, if I open it more it idles way high.

I even tried setting it the same as my revo and it does the same thing, that's what is confusing me.

And ill try the lsn in the morning and post up if I'm still having issues, thanks guys

 

[PaulC]

How does it behave if, after letting it warm up, you give it the boot? I realise it will cut out when you hit the brakes, but that's not important at the moment.

If it takes off and screams to full speed with virtually no smoke at speed, I would not bother touching the LSN, I'd richen the whole thing 2-3 hours and take it from there. (ie. the HSN out 1/8 to a 1/4 turn).

My new Picco should have been way rich as it didn't move much lean from factory, but it started to idle high and turned out to be slightly rich. I haven't touched the LSN and as I understand it, if you car accelerates off the line from 0 to WOT without hesitation or stutter, LSN is pretty damn close.

 

[darkslayor24]

well, nothing was said about the engine running erratically at speed. my thought is that the linkage at idle, isn't even resting on the idle screw. and that is why the idle is high. and that would be why the brakes cut the engine off, is because when brakes are applied, the screw is so far back, that it cuts off when the throttle backs off. to me it also seems right because he did mention an engine change which would change the linkage setup. but ok...

heres a quick tuning tip/guide
run the vehicle until the engine is up to temp.
make sure that you have lots of top end, but plenty of smoke from the exhaust. once the highs speed is set. then work on the low speed.
the engine should not bog when going from neutral throttle to wot
your engine should have a fairly smooth acceleration.
smoke is the main factor.
you need to see smoke or you are too lean

 

[NitroArsenal]

I don't know much about the sport, but looking at my t-maxx and reading, my money is on the servo/linkage. It is definitely important to make sure the servo is not slightly opening up the carb, most ways i would tell is by turning everything on to let the servo's set, shut it off and try to push the carb closed, or other tests such as that, to make sure the servo is not keeping it slightly open. Never want to adjust your idle by the throttle trim (servo setting) or you will always have problems.