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Old T-Maxx 3.3 issue.

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Old T-Maxx 3.3 issue.

Old 12-04-2017, 04:42 PM
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Default Old T-Maxx 3.3 issue.

Hey guys, so coming here as a last resortish kinda thread. I have had my T-Maxx for around 6-7 years now and recently have got here back up and running. Now, she'll start when she wants, but won't hold. Just today I installed a pull-start and got rid of that ez-start bull shit hoping that would fix my problems, thinking the wire to the glow plug wasn't getting currents. Got everything good, went to go start here up and eventually got here going after 30-40 pulls. She is unable to hold an idle, immediately starts to move forward (considered it a tuning issue, but coming to think it may be something more after much nitpicking around with her). So, came here looking for maybe some insight on why she is SO hard to get started and then keep going. I prime the engine every time and I've also heated the engine before starting, with no luck. Any ideas what could be causing the such time consuming and irritating start up? I mean once she gets going, she goes. But just can't hold an idle nor start without tons of pulling.
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Old 12-04-2017, 05:01 PM
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First I would take apart and rebuild the engine, if it has been sitting for that long it probably needs a rebuild, check compression and for any rust, use a super-high grit sandpaper to get it off, I think traxxas said 1200 grit, here's the official post https://traxxas.com/support/TRX-Engine-Rebuild-Instructions-0"Remove this and the quotes"
I'm not allowed to post URL's yet, remove the quotes and stuff after the "0"
After that I would set the carb back to factory spec, maybe lean it out a tiny bit since it's already been broken in, also, sounds like you idles to high, find a large paper clip, they are exactly 1mm, but that in a carb and set it to have a 1mm opening, maybe a tiny bit less.
If that does not work, take your transmission apart, does yours have reverse, if so I would remove it, it's only $12 ish and greatly improves the performance, also check your spur gear mesh.
One last thing, use new fuel, if you are already that's fine, the methanol in the fuel sucks up water in the air and decreases performance and does get "weaker" over time. So always put your fuel cap back on
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Old 12-04-2017, 10:07 PM
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Originally Posted by BrickitSAM View Post
First I would take apart and rebuild the engine, if it has been sitting for that long it probably needs a rebuild, check compression and for any rust, use a super-high grit sandpaper to get it off, I think traxxas said 1200 grit, here's the official post https://traxxas.com/support/TRX-Engine-Rebuild-Instructions-0"Remove this and the quotes"
I'm not allowed to post URL's yet, remove the quotes and stuff after the "0"
After that I would set the carb back to factory spec, maybe lean it out a tiny bit since it's already been broken in, also, sounds like you idles to high, find a large paper clip, they are exactly 1mm, but that in a carb and set it to have a 1mm opening, maybe a tiny bit less.
If that does not work, take your transmission apart, does yours have reverse, if so I would remove it, it's only $12 ish and greatly improves the performance, also check your spur gear mesh.
One last thing, use new fuel, if you are already that's fine, the methanol in the fuel sucks up water in the air and decreases performance and does get "weaker" over time. So always put your fuel cap back on
Yeah, I may just go ahead and rebuild it. Not sure what parts I'll be needing to replace based just off the problems I've been having. Piston and sleeve should be good so hopefully won't need to re-break the engine in. Mine does not have reverse, can't recall if it did or not when I got it, my guess is no. It's about 7 years old with the 27mhz transmitter. Yup, fuel should be all good. Although when I went back in the garage a month back or so to get my RC things I had jelly'd nitro still in the tank, so that kind of wasn't to good. Cleaned all that out and she seemed to be fine after putting new fuel in here other then the current problems I have. Traxxas...
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Old 12-05-2017, 07:32 AM
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Ok, unless you have not put 7+ gallons of fuel through it the sleeve and piston should be fine, only thing I can say now is rebuild the engine, reset carb, and check the bearings, they should not feel grainy at all, or when everything else is out of the engine, put the crank in, then try to wiggle the crank up-down by the output and if it moves, replace the bearings.
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Old 12-05-2017, 07:58 AM
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I would add new fuel tubing as well. Along with engine and carb rebuild. New plug. How old is the fuel?
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Old 12-05-2017, 04:35 PM
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Originally Posted by Notbrick View Post
I would add new fuel tubing as well. Along with engine and carb rebuild. New plug. How old is the fuel?
Fuel isn't old, guess I'll end up just rebuilding the engine and making sure everything is good in there. Considered that my last resort, but guess I'm at my last resort. Traxxas...
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Old 12-05-2017, 06:38 PM
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1. Not idling and moving forward while idling are symptoms of a broken clutch spring.
2. Replace the glow plug
3. Use fresh fuel
4. Set carb idle gap to .5-.6mm and blow through fuel line to carb at idle. Air should barely get through. Open carb wide open and blow again. Air should move through easily. If air doesn’t move easily, open needles 1/2-1 turn and try again. If no joy, remove the carb from the engine, disassemble, clean with acetone, and reassemble.
5. Check bearings for grittiness. If crank turns smooth, bearings should be good. If crank turns rough, replace bearings.
6. If you get it primed right, glow driver is fully charged, and glow plug is new/known good, it should start and run within 4-6 pulls easily. My 3.3s start in 2 pulls religiously - one has 4 gallons on it and the other has over 8 gallons on it.
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Old 12-05-2017, 07:30 PM
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Originally Posted by SlowLST2 View Post
1. Not idling and moving forward while idling are symptoms of a broken clutch spring.
2. Replace the glow plug
3. Use fresh fuel
4. Set carb idle gap to .5-.6mm and blow through fuel line to carb at idle. Air should barely get through. Open carb wide open and blow again. Air should move through easily. If air doesnít move easily, open needles 1/2-1 turn and try again. If no joy, remove the carb from the engine, disassemble, clean with acetone, and reassemble.
5. Check bearings for grittiness. If crank turns smooth, bearings should be good. If crank turns rough, replace bearings.
6. If you get it primed right, glow driver is fully charged, and glow plug is new/known good, it should start and run within 4-6 pulls easily. My 3.3s start in 2 pulls religiously - one has 4 gallons on it and the other has over 8 gallons on it.
Hmm, okay. Thank you, very valuable feedback. I am going to check the clutch out before opening up the engine. My original guess was something with the clutch, but assumed I was wrong when no one else mentioned it. Thanks again.
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Old 12-05-2017, 11:18 PM
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Originally Posted by CBren32 View Post
Hmm, okay. Thank you, very valuable feedback. I am going to check the clutch out before opening up the engine. My original guess was something with the clutch, but assumed I was wrong when no one else mentioned it. Thanks again.
It’s common sense. If the engine isn’t revving up much if at all or won’t hold an idle but moves forward, it’s pretty obvious to someone experienced that checking the clutch is th first thing to do. When the first responses are to rebuild the engine and check for rust (and sand it off with sandpaper); be wary of what advice you take out of the gate.

If the clutch checks out, check the throttle linkage and carb slide idle gap. Make sure that the gap is .5-.6mm and the linkage is returning it to idle without having to hit the brakes to close it to the idle stop and also ensure it’s working freely and not hanging up anywhere.
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Old 12-08-2017, 09:34 PM
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Originally Posted by SlowLST2 View Post
Itís common sense. If the engine isnít revving up much if at all or wonít hold an idle but moves forward, itís pretty obvious to someone experienced that checking the clutch is th first thing to do. When the first responses are to rebuild the engine and check for rust (and sand it off with sandpaper); be wary of what advice you take out of the gate.

If the clutch checks out, check the throttle linkage and carb slide idle gap. Make sure that the gap is .5-.6mm and the linkage is returning it to idle without having to hit the brakes to close it to the idle stop and also ensure itís working freely and not hanging up anywhere.
Hey there, so was a bit busy lately but ended up taking out the clutch slippers and springs. There were no problems there. Would there be anything else that would merit this problem, or is it time to rebuild this engine? thanks
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Old 12-08-2017, 10:37 PM
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Originally Posted by CBren32 View Post
Hey there, so was a bit busy lately but ended up taking out the clutch slippers and springs. There were no problems there. Would there be anything else that would merit this problem, or is it time to rebuild this engine? thanks
Tackle the other things on the list I gave. Jumping right to rebuilding the engine may prove more costly than is necessary and may not fix the problem.
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Old 12-09-2017, 01:40 PM
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Sorry, yes checked everything with throttle linkage and carb. Even took off the cleaned it and sprayed it with WD40 to make sure it would open and close freely. Quite confused on this engine, can't think of what the issue could be. I am going to just get new clutch slippers today, because supposely they should form a complete circle. Mine seem barely worn down, but gonna replace them either way I guess gotta go to hobby store anyways. Anything else you can think of causing this issue? Also, when I tried starting it I just can't even get it started anymore. Never wants to pull fuel to the exhaust, so I always have to blow it through. I am going to clean out the exhaust tonight with cleaning foam and see if there is maybe built up dirt in it. Seems a bit dirt, so thinking there could be something blocking air flow, but I don't know. Thanks.
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Old 12-09-2017, 08:38 PM
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Keep the WD40 away from model engines. If you’re going to oil anything on an engine, use air tool oil, sewing machine oil/3-in-1 oil, or regular automotive transmission fluid. WD40 evaporated leaving virtually nothing behind.

As long as the muffler pressure fitting from the exhaust to the fuel tank is clear of obstruction, there’s nothing that needs to be done to it. Most tractability problems are related to the glow plug or the carburetor - whether it be improper needle settings and/or idle gap, or dirty fuel inlet/clogged fuel passages. The latter is rarely a problem.

I prime all of my engines by blowing into the pressure line from the muffler to the tank. Blow until fuel reaches the carb and go 1/2-1 second more. Reconnect the pressure line and start the engine. If your needle setting is too lean, it should fire up, run off the prime, and quit. Open idle needle 1/2 turn and try again. You can use the factory carb settings to get started, but if you do that, lean the main needle 1 turn in and 1/2 turn leaner on the idle mixture. Make sure the idle gap is no larger than .6mm to start and the throttle linkage is working properly and smoothly. Ensure the throttle is closing to the idle stop on its own with the throttle trigger in the neutral position. Ensure you have a little bit of throttle deadband in the linkage!!
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Old 12-09-2017, 08:48 PM
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Originally Posted by SlowLST2 View Post
Keep the WD40 away from model engines. If youíre going to oil anything on an engine, use air tool oil, sewing machine oil/3-in-1 oil, or regular automotive transmission fluid. WD40 evaporated leaving virtually nothing behind.

As long as the muffler pressure fitting from the exhaust to the fuel tank is clear of obstruction, thereís nothing that needs to be done to it. Most tractability problems are related to the glow plug or the carburetor - whether it be improper needle settings and/or idle gap, or dirty fuel inlet/clogged fuel passages. The latter is rarely a problem.

I prime all of my engines by blowing into the pressure line from the muffler to the tank. Blow until fuel reaches the carb and go 1/2-1 second more. Reconnect the pressure line and start the engine. If your needle setting is too lean, it should fire up, run off the prime, and quit. Open idle needle 1/2 turn and try again. You can use the factory carb settings to get started, but if you do that, lean the main needle 1 turn in and 1/2 turn leaner on the idle mixture. Make sure the idle gap is no larger than .6mm to start and the throttle linkage is working properly and smoothly. Ensure the throttle is closing to the idle stop on its own with the throttle trigger in the neutral position. Ensure you have a little bit of throttle deadband in the linkage!!
Okay, will execute everything you have down here tomorrow morning. When trying to start the engine, took off the air filter and noticed something weird but may just be my bad eyes or something. When I turn the idle screw all the way in or to factory, seems as if the carb gap doesn't change. I am not sure how that could be, makes no sense to me so guessing it's just my old crappy eyes but hell might as well bring it up. Really appreciate the help man, you're the best.
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Old 12-09-2017, 09:06 PM
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The idle gap adjustment is the screw that goes into the side of the carb at an angle. The idle mixture needle is in the end of the slide valve of the carb where the throttle linkage connects.
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