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TMaxx will not idle down

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Cupooterluvr

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My TMaxx, which was in great tune before today, will not idle down. It might be because I replaced the stock traxxas glow plug with a McCoy 59 plug, which was recommended by the man at the LHS. I would like to know if this is the correct plug, or if I should go back and get the Traxxas plugs.

I tried decreasing the idle set screw, and richening the LSN, along with fully applying the brakes when setting the idle. It just stays where it is. I then tried letting it cool and restarting it, at which point the idle was still very high, but it would cycle from low to high.

The idle isn't high enough to fully engage the clutch, but it is high enough to make the clutch shoes drag on the bell.


Side note: I flooded the engine when starting it today, but I think it was just because I primed it too long. Also, I use a separate glow ignitor (1.2 volt rechargeable nicad). The ambient tempurature was approximately 5 to 10 degrees F cooler today than when I ran it last.

Any help appreciated.
 
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I don't think the plug is a problem, the 59's have been really good for me. Have you removed the air filter to look and see the throttle vavle gap in the carb and see if your ajustments are changing it? Are you sure nothing else changed? Kinda sounds like you might have developed an air leak.
 
thats exactly what it sounds to me, an air leak will take over your motor, idle up and down with no option to control the motor, i would start there
 
I would agree. Check the seal on the tank lid, fuel line connections, fuel filter, carb neck and backplate. Seal the neck and back plate with red RTV and let it cure for 24 hours. Restart, retune, repost.
 
Will Permatex 2B "gasket sealant" compound work? It says on the tube it is used for engine component seals, and on the front it says "pliable non hardening". I ask because my dad already had some in his toolbox.
 
Unfortunately, sealing the engine and carb neck did not stop the leak. It is still there, though it isn't as noticeable. Now I'm thinking it may be either the lines, fuel filter, or one of the needles that is leaking. I'm going to wait for the engine to cool then unscrew everything and check the gaskets.
 
are the needles back to factory settings, it'll be easier to know whats going on with them like that, after they are at stock settings turn lsn counterclockwise 1/4 of a turn let us know what happens
 
Checked the lines, fuel filter, and gaskets-- none are messed up. I'll try stock settings tomorrow like RC said. Unfortunately it looks like rain so no runs for me today.

Got my first taste of nitro cleaning out the lines. Note to self: don't get it on mucous membranes. :LoL:
 
I think its the lsn screw personally. I had that problem and swore it was an air leak, set the needls back to factory and bam ran like a champ. When the lsn gets lean it increases the idle, which is what sounds like your problem. Also, if I'm not mistaking, there is a gasket(o-ring) on the idle screw on traxxas mills. I have read cases where they crack. Might want to check that if nothing eles works out. I'm going to check my back up 2.5 when I get home to confirm the o-ring thing though. Good luck and keep up informed.

Bryson
 
Ok, I'll be sure to check that tomorrow. I was thinking it could have been the LSN too since it sounded a bit lean when decelerating.

Hey, at least I have a nice, tightly sealed engine if it ISN'T an air leak.
 
That is pretty awesome looking, but the reason I asked about the Integy pipe is because I actually wanted a rear exhaust.
 
i wouldnt really go with a dual exhaust, it doesn't great much backpressure which the motor and exhaust needs, i would go with the carbon one that cupooterlurv before the dualies, or try to find a good stock replacement, the stock exhaust on the revo is nice think its interchangable but might want to look for something like that
 
I asked momanddad for a Resonator for Xmas.... and judging from the tower hobbies pamphlets that seem to be floating around everywhere I think something came for the maxx.

On the high idle issue... I know that a high idle is bad for cooling but I was thinking of getting stiffer clutch springs to both counter the effects of a high idle and give it a better jump off the line. Would this be a good idea?
 
I had the same problem with my 1/8 Buggy. Would not stay on a steady idle and was quite high. I thought the solution was to keep richening the LSN, but this was going the wrong way. Turns out that the LSN was set rich at the factory for breaking in purpose and the LSN actually needed to be leaned out until the idle was steady, then the idle speed adjustment screw was turned out to lower the rpm of the idle.

This info below from ParisRacing solved my problem.

Tuning tech: carb Needle balance
We get dozens of tuning questions from around the world at Paris racing daily, The number one questions is, were do I set my needles on the
carb?
Unfortunately there is no such thing as a definitive universal setting for any engine!
Every application will have it’s own unique requirements, even two IDENTICAL set ups can and most likely will have at least slightly different
settings.
Please see tech tips following the article below [from our web site]
I would like to address what seems to be the # 1 mistake we encounter in engine tuning:
Carburetor Needle balance:
It has come to our attention some racers are making the mistake of setting the idle speed opening to wide [high idle] and setting the bottom
end too rich!
This will give a false normal idle speed even though the speed is set to high because it “loads up” the engine with excess fuel causing the idle
to be lower than set!
The end result is a very unstable idling engine that surges and may cut out as full throttle is applied because the over rich bottom end can
disguise a too lean TOP end setting!!!
Let’s address this a little more in depth!
Idle speed opining set too wide:
It is possible too set the idle screw adjustment in to far but yet the idle speed is not high!
Even though the air regulation [carb barrel or slide] may be set to a position that would normally equal a vary fast idle, the idle is low because
the low speed mixture adjustment is set so rich that the engine loads up with excess fuel and the engine goes into what’s commonly called a
four cycle idle.
One tell tail sign of this is if after revving up the completely warmed up engine it tends to idle fast for a few seconds then drops to lower idle
speed.
[Here we go again with the written sound effects :-)]
Something like da..da..da..da..da..da..da..da then it drops to da….da….da….da [if it were sheet music it would be like dropping from 8 beats
per measure to 4 beats per measure]
If you start leaning the bottom end a little at a time [then repeat the revving up and idle test] and it takes longer before the idle drops your going
in the right direction!
Eventually as you keep leaning the bottom the idle will stay to high, now it is time to lower the idle to were it belongs by re adjusting the idle
screw!
CAUTION!!!!
Now that you have the idle set correctly the top end may be too lean!!!
 
Last edited by a moderator:
I think that's what the problem was. Carb opening was rather wide, about 1.5mm. I leaned it out LSN and decreased idle gap. Will RRR tomorrow.
 

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