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Motor question, going south, or bad tune?

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Old 03-27-2008, 04:07 PM
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Lordmik
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Default Motor question, going south, or bad tune?

Ok, let me start off by saying I'm way over geared. Some of ya'll know what I did, but for those who don't, I'll explain. I took the suspension off my Volcano EPX and transferred it to my Tornado XL chassis, cuz I wanted a nitro truck. I still have the orig tooth count clutchbell on it, 16 or 17, what ever it is. I know I'm geared high. With that being said, here's my problem. I start up the engine, and it idles great, pulls great, but after about 5 or 6 min, it won't rev out. It revs some, then sounds like it's bogging and won't rev hard. It still pulls good, but won't climb into the higher rpms. But it will for the first several minutes. Now, if I drive it around easy after that 5 or 6 min, after a few min it'll start to rev good again, but never as good as when it's cooled off and then run again. When I say cooled off, I mean still warm to the touch, usually long enough for me to get it into the shop for fuel. So, does this sound like an engine on it's last legs, or maybe I'm too rich/lean? I've got a pretty good trail of smoke, even when it's having this problem. Also, I'm pretty sure it's not overheating because I can wet my finger and run it over the head after a good run, and it doesn't sizzle and pop, it just evaporates off. Any suggestions guys? I don't really want to buy a new motor, and I don't want to ruin this one if it's not already. Thanks

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Old 03-27-2008, 04:30 PM
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Default RE: Motor question, going south, or bad tune?

judging by the sluggish low end and the evaporation (too hot), I'd say the high speed needle is too lean
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Old 03-27-2008, 04:37 PM
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Default RE: Motor question, going south, or bad tune?

Actually that depends on how fast it evaporates. 3-5 seconds on a drop is about where to be. popping and sizzling is bad. if the top end is what is only suffering then you could either be too lean or too rich. The high speed needle needs to be set about 2 1/2 turns open from the closed position. But since you say that it looses power after it warms up that sounds like a worn out sleeve. how does it perform when it is cold and how does it tune when it warms up. a worn out motor won't hold a tune for anything after it warms up.
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Old 03-27-2008, 04:45 PM
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Default RE: Motor question, going south, or bad tune?

It has little power when it's warmed up good, say 5 min or so of jumping a ramp, etc. Runs strong before that. And then gets better if you just drive it easy for a couple min. I'll try resetting my hsn and see what happens. My lsn is way in though, in order for it to idle at all.
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Old 03-27-2008, 04:58 PM
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Default RE: Motor question, going south, or bad tune?

Back out your low speed needle to just under flush with the chrome collar about 1 turn in from flush. then you will need to raise your idle some. it should idle like that. your throttle trim might need to be adjusted too. that might be all thats wrong
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Old 03-27-2008, 05:24 PM
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Default RE: Motor question, going south, or bad tune?

You use the idle adjustment screw to get proper idle. The low speed needle should be close to flush with linkage flange. Get your HSN/high speed needle tuned before you touch low speed needle. When you start tuning for performance, you only want to adjust HSN A hair at a time. When looking at HSN picture the face of a clock around the needle head and adjust in one hour incraments. The same with LSN. When you have it running how you want it at high speed, adjust LSN so that when you squeeze your throttle trigger you get a nice crisp engine rev.. Your idle adj. screw should leave about a 1mm opening it carb. throat when at neutral. Let us know how it goes.
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Old 03-27-2008, 07:52 PM
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Default RE: Motor question, going south, or bad tune?

Thanks for all your help guys. I think I was way lean on the lsn, and rich as all get out on the hsn. I got 'er ripping again!! Thanks!!!




P.S. Hey Macanan, those shocks are friggin awesome!!!!
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Old 03-27-2008, 09:22 PM
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Default RE: Motor question, going south, or bad tune?

To mee with you saying that you are too overgeared sounds like you are overworking the engine and its overheating. Not because its lean but because its working real hard to move a truck thats overgeared. I dont think its anything wrong with your engine. Its definately overgeared adn it will make that engine work hard.
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