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Can't get the truck to idle at all!

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R

Runaway Jim

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Hello,

I recently leaned my engine out a little bit and as a result, initially, the transmission wasn't shifting into second gear. i tightened the slipper clutch nut and adjusted the shift point which seems to have fixed the shifting problem. Since then though... no idle!

The truck won't stay running at idle. I've tried adjusting the idle needle on the engine along the whole spectrum of settings, close to closed and all the way close to wide open. No setting allows the truck to idle at all. When I start it up I have to be quick with the trigger or else it stalls immediately. It runs fine when it doesn't stall, just no idle at all.

The only other things I've done to the truck recently is add the teckno sway bar kit and the traxxas resonator tuned pipe. That's it. The clutch seemed to be stuck engaged one time for about 30 seconds about two weeks ago but that hasn't happened since. Any ideas?

I'm new to tearing into the truck, this is my first vehicle, so if what you suggest I try involves tearing the engine out or getting into the clutch bell, if possible let me know what I may be looking for as the problem so I don't, you know, see it and not know that the problem is staring me right in the face.

Thanks in advance to anyone who responds!
 
Is your throttle servo set to its normal position? If it is and the carb is open a lot, you can change the position of your servo arm by taking it off the servo and setting it into a position where the carb opening is fine.
 
ohmygahitscoby said:
Is your throttle servo set to its normal position? If it is and the carb is open a lot, you can change the position of your servo arm by taking it off the servo and setting it into a position where the carb opening is fine.
Click to expand...

how come adjusting the servo would need to be done if the truck used to run fine before i tuned the engine to run a little leaner? is it possible that i tightened the slipper too much and things arent' loose enough to allow the engine to completely disengage from the clutch while at low speed/idle speed?
 
Coby knows what he's talking about so check that.

If you changed your exhaust pipe that will affect your tune also. Whenever I can't get my engine to run properly after replacing something, I set the needles back to the factory setting and go from there. For me it's usually faster than trying to figure out which needle (hsn or lsn) the change affected.
 
i checked the manual and will set them hsn and lsn to factory tomorrow. 4 turns out on the high and flush with the inside of the ring around the lsn. you're right, it's a place to start. i may have missed it but where should the idle screw be set to go along with the hsn and lsn factory settings?
 
For the idle, the manual won't say anything. Take your air filter off and look inside the carb, turn on your TX and then your RX and check the amount of 'gap'. It should be about the thickness of a credit card. Oh yeah, also make sure your throttle trim is set in the middle on your TX before checking the gap. You can adjust the idle screw to make the gap bigger or smaller. With all 3 set to factory you should be on the rich side but in the ballpark.

Let us know how it turns out. What kind of fuel are you using?
 
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MrClean said:
For the idle, the manual won't say anything. Take your air filter off and look inside the carb, turn on your TX and then your RX and check the amount of 'gap'. It should be about the thickness of a credit card. Oh yeah, also make sure your throttle trim is set in the middle on your TX before checking the gap. You can adjust the idle screw to make the gap bigger or smaller. With all 3 set to factory you should be on the rich side but in the ballpark.

Let us know how it turns out. What kind of fuel are you using?
Click to expand...

Hello all,

Thanks for all the advice on things to check. I got back to the truck today and got it up and running. Basically there were two things wrong. First, I'm an idiot. Second, one of the pads on the slipper clutch managed to somehow fall off so the gear was spinning off center. I went to my local hobby shop which had the slipper clutch rebuild kit in stock, $5, and fixxed that.

Reason I'm an idiot is that I was turning the idle needle the wrong way to increase idle. I was decreasing it the whole time. As I mentioned...IDIOT! I reset the two other needles to factory as well as turning the idle screw the right way to increase it and it's running and idling. The last remaining problem is that after I let it idle for 10 to 15 seconds and then give it some gas it stalls out. I imagine it's a bit to rich and the engine has too much in it after idling. I'll work on it a little more tomorrow and if worse comes to worse the guys at my hobby shop said that I should bring it down and they'd be willing to let me work on it with them to figure it out and learn something at the same time. I love my local hobby shop!

I think that a little more fine tuning on the engine and it'll be fine again. I'll post again to let you all know. So far your advice has really helped. Thanks again everyone...

RJ
 
You sound like me RJ, I do so many dumb things and then figure them out later. You're not an idiot, just learning and that's a good thing. You pretty much figured it out by yourself, we just helped with the tuning part. My lhs is the same way, they used to tune engines for people, but that didn't work out so well for them, now they offer to help you with tuning yours. Which I think is a much better idea, that way the owner of the rig learns how it works and what to look for.
 
Hey everyone,

I finally figured out what the problem was with my engine. Somehow, somewhere along the way a small piece of the piston head chipped off and banged around inside the cylinder for a few seconds before getting blown out with the exhaust. My local hobby shop ran the truck with me and suggested, something could be wrong with the piston and sleeve because when it ran it ran like a bat outta hell but it would stall frequently and was an absolute bear to start back up again immediately but would start right up after cooling. The compression at high temps or normal running temps was compromised. Once I got into the engine to replace the piston head and sleeve I also noticed the damage to the bottom of the cooling head. So I've got the new piston head and sleeve in but have to wait until a shipment tomorrow for a new cooling head. Here's a picture for all of your entertainment.

View attachment 6419
View attachment 6420
 
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Is that piston head rough to the touch? It looks like it's been hit by a sand blaster, all pitted. I don't think I've seen one like that ever before.
 
Yes sir, it is. I can fit the peaks and valleys of the pits on the piston head right into the matching peak and valley pits on the bottom of the cooling head. Fits like a glove! On the side of the piston head there's a small area that has a chunk out of it. Chunk lends itself to being large but believe me, it's small. Evidently big enough to cause all of this damage though. I thought you'd all think this was interesting to see. At least I know how to rebuild an engine now.:D

By the way, there was discussion around me taking a dremel to the piston head and the cooling head to smooth them over again but it was decided that the compression would never be close to correct again after that and it may cause damage to other parts of the engine running it that way. I'm gonna keep the damaged parts and when I upgrade the engine down the road I'll try to smooth it over and see how it runs afterward... if at all.
 
That's the craziest damage I've ever seen. Keep the piston, they make a cool key chain. I thing you're right, the compression would never be the same, if it would run at all. Hard to tell how bad the pitting is from the pics but it seems pretty drastic.
 
i couldn't seem to get zoomed in enough to really show how bad the pitting is. if you click on the pics they get bigger and maybe a little easier to see. overall though i'll say this. i'm relatively new to this hobby and as soon as i saw this damage i knew that there was no way i'd run with this engine again unless i replaced the cooling head along with the piston sleeve and piston head. in short... bad, bad, bad...very bad! :whhooo:
 
When you have the engine back in, let us know how it's running, and we'll get it tweaked for you. Just remember, a new piston and sleeve needs the same break in as a brand new engine.
 
thanks for the heads up on that. i really didn't know that. glad i posted this stuff or else i'd have blown through this new stuff as well. i hope to have it all back together tomorrow and will work through the break in over the weekend as long as the weather is good. i gotta dig out that traxxas dvd to make sure i remember the right procedure...
 
hey guys, update on the rebuild. got the cooling head today, oiled up the sleeve and piston head and put everything back together. i reset the hsn to 5 turns out and the lsn to 1.5 turns out. primed the engine for about 2 seconds and then tried starting it. it fired right up. it sounds really good but idle is an issue again. i think it's too rich. i tset the hsn to 5 turns at the suggestion of my hobby shop guys. I didn't have time to run through any of the break in today but will start tomorrow. it stays running with a little gas but i can tell it's gonna run real sluggish to begin with. i'll lean the hsn a bit so it won't keep stalling with too much fuel and see how it goes. overall, so far so good. i was really happy it fired right up when i got it all back together especially since this is my first time tearing apart and rebuilding a nitro engine...
 
Hey Jim, good to hear you got it back together and it's running! 5 turns on the HSN might be too much, Traxxas sends it out with it set to 4 and even that's usually a bit rich. On the LSN, not sure about the # of turns but the screw should be flush with the surrounding area. Running rich during break in isn't a bad thing, make sure you put the piston at BDC as soon as you shut it off. I didn't in the very beginning and I think I lost some of my pinch due to that.
 
how will i know that i've got it at bottom dead center? at least i think that's what bdc means....
 
Since you have the motor back together, take the glow plug out and use a thin screwdriver...... or anything that will fit down inside the cooling head. (just make sure it's clean...lol). Rotate the flywheel until you feel the piston go down to the bottom, with a new sleeve it might be difficult to turn by hand when the piston is at the top. With it at the bottom of the stroke, take a magic marker, finger nail polish...anything permanent and place a mark on the flywheel (usually it's easiest done from the bottom of the vehicle). Whenever you stop your rig, the first thing you should do is rotate the flywheel until you see the mark. Sometimes you need to use a screwdrive on the flywheel if the compression is too much to move by hand.
 

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