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  1. #1
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    Just a little tuning help, please?

    Hey all, it is me again. You know, the guy who asks all the dumb questions.



    Anyways, I'm tuning the engine on me and my friend's tec. Mine is tuned perfect, but his is having a little more of a hassle. I think he tried to tune it himself, and it is WAY out of whack. So, I come to you with the following steps I've taken, please correct me on any of them if I'm wrong.


    1. Set HSN to CLOSED(lean it all the way until you can't turn the needle). Set the LSN screw to flush with the inner ring. Set throttle trim to the point where it just starts to apply the brakes.

    2. Richen the HSN 4 turns out(counter-clockwise, A.K.A. richen). Started engine. Car started up, ran for two seconds, and shuts off. Raised the idle an 1/8th. Car now runs while standing still(after warmed up to 180 degrees) for about 15-25 seconds, then will cut out. I'm leaving that idle alone for now.

    3. I eased on the throttle. You know, ease to 1/4 for 2 sec., then to 1/2 for 2 sec., then to 3/4 for 3 sec., then punch it to full. Everything is okay that way. Plenty of smoke.

    4. Instead of easing it on, punch it. She stutters a bit off the line. So naturally, I richen LSN 1/8th. No more stutter off the line. Do the pinch test, and she shuts off like she's supposed to. About 1-2 seconds, higher idle, then poof, shuts off. Sounds to me like the LSN is tuned right.

    5. Still doing the punch it way of throttle Now she's fine off the line, BLUE smoke like when she was new. But after she gets into second gear(about 1.5-2 sec. after I punched it all the way, and around 30-35 MPH) The engine just completely shuts off. No stutter like when the LSN was lean. So I'm assuming that it is too rich on the HSN, is this correct? I wasn't able to go any farther with it, started getting dark, and I didn't want to ruin any adjustments in the dark. lol

    So I need help with getting it to idle longer than 20 seconds or so. I need help with the cut off at(or around) second gear. Also, the temp after a tank of tuning was 204. There wasn't any excess fuel spitting from the exhaust, which is why I questioned myself about it being too rich on top end. Though it does have nice smoke trail the whole way, but no excess fuel. Throttle trim is set to dead 0. Also, as a side note, does anyone have a good toe-in and/or camber guide?

    Thanks in advance, all.
    -J.D.S.


    EDIT: Oh, also something I forgot to add about engine noise. After bring her past 3/4 throttle and bringing her to a stop, the idle will be high for about 5 seconds after stopping, then lower to its usual mumbling tone. This may help you guys to give me a better diagnostic.
    Last edited by J.D.S.; 03-13-2007 at 07:53 AM.
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  2. #2
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    Man, he's still got the same problem, and I don't know what to do with it. It is un-responsive to tuning the HSN. Same problem at 3-1/2 turns as there is at 4-1/2. I don't know what's wrong with it. It just sounds like it runs out of fuel when you punch the throttle. The car is only about 3 months old, about 2 gallons of fuel through it, and that's being generous.

    The only thing that's out of the ordinary on the car is that there seems to be an excess of bubbles in the fuel tank. We replaced the fuel lines on the car, still the bubbles. Is the tank not sealing!? Any advice would be appreciated.
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  3. #3
    RC Champion
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    You have air leak or the tank is not sealing, also check all fuel lines, exhaust leak. The air leak may be from the back plate behind the easy start or the front bearing or by the carb. also chech where the HSN threads into the carb and make shure it is not loose.

  4. #4
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    replace the fuel line and the pressure line. If bubbles persist, lengthen the pressure line.

  5. #5
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    Yeah, we replaced the fuel lines last week. We still have some leftover tubing, so maybe we should lengthen the pressure line? Will that help?
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  6. #6
    RC Champion
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    Quote Originally Posted by J.D.S.
    Yeah, we replaced the fuel lines last week. We still have some leftover tubing, so maybe we should lengthen the pressure line? Will that help?
    Air leaks mess up everything, so the first thing is to make sure the fuel lines and backplate, carb, etc have no leak issues like mentioned earlier. Sounds like you have done that.

    So, given the info you gave about engine revving when stopping and the amount of smoke and way it is reacting, I would say that you have a combo of too lean LSN and too rich HSN. You must set the HSN first or the LSN will not be correct. What happens is that you overlean the LSN to sort of choke off fuel flow at idle which compensates for the over rich condition and delays the inevitable flooding. The overlean LSN is the only reason why it is still idling for at least 20 sec. I beleive that you will find leaning the HSN will then show a lean LSN and it will die almost instantly when punching it, so I would richen the LSN a bit if this happens, but definitely lean out the HSN. Once it stays running under acceleration, just keep making full speed runs and keep leaning the HSN until it's good, even if the car is a bit boggy off the line. It should clean out and then go ballistic. Once you hit this point, you can start leaning the LSN again. Remember to keep adjusting the idle as leaning the needles will naturally begin to increase the idle.
    -Terry
    "The best part of wakin' up....is Nitro" i

  7. #7
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    Terry, if we even so much as RICHEN the LSN 1/8, the engine won't stay running. So maybe this is the case? Too lean on LSN and too rich on HSN?
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  8. #8
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    Quote Originally Posted by J.D.S.
    Terry, if we even so much as RICHEN the LSN 1/8, the engine won't stay running. So maybe this is the case? Too lean on LSN and too rich on HSN?
    Yes, that is what I was saying. So you need to richen the LSN and lean out the HSN. It does not hurt to have the LSN too rich initially. It is controlled first by the HSN. Think of the 2 needles as valves in your garden hose. The main valve at the house is the HSN and the sprayer on the end of the hose. If you want the right flow from the sprayer, you must first have enough or not too much from the main valve.

    Your idle screw is probably set too high also to keep it from flooding. You will need to readjust it as you start leaning out the HSN. And again when you are ready to Lean out the LSN.
    -Terry
    "The best part of wakin' up....is Nitro" i

  9. #9
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    I don't get it. LOL I'm sorry, I just don't get his car. We've tried again. Leaned it all the way to 3 and 1/2, and richened his LSN by 1 turn. The car ran WORSE. I really don't get it. I put it back to the way I had it, which is the best it runs. 4 and 1/8th on HSN, and 1 and 1/2 on LSN from flush. Idle is about 1-.5 mm out from the carb(no I've never measured it, but if I had to guess, I'd say it is that much.) Car in this set-up idles PERFECT, gets off the line perfect, smokes perfect, just when she hits second gear(if you punch it from dead stop) it shuts down. When I tried leaning the HSN and richening LSN, it just got terribly worse. Couldn't even keep the car running, not even by raising the idle. Tried then leaning the LSN, still wouldn't run. Tried the HSN at 3 and a half, 3 and 3/4, and 4. Same problem ALL DAY LONG. Guy at the hobby shop said it may be a carb leak, brought along a carb that worked from my old motor, same adjustments, same problem. We already replaced the lines, so I guess we'll lengthen the pressure line. If problem persists, I swear we're taking it to the shop...lol Any other words of advice? Please, we're getting desperate.


    Totally off-topic, but my car threw a front drive belt AND an exhaust coupler. Ran it two wheel drive. Never ran a 2wd tec before. Boooooy is she squirrly. :P
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