DT94588

Hi guys,

So after several tries at getting the low speed and idle speed set, I'm completely baffled.

I have a Losi XXX-NT with a Mach .15 engine. Following most engine tuning instructions, I warmed the engine up running a complete tank of nitro through it.

Then, I tuned the high speed needle so that a nice blue smoke comes out the exhaust while running at higher speeds.

At the low end, I experience the following. When I "blip" the throttle (pull it to full open, then let it go back to idle), the engine dies.

I thought I was running to lean at first since I couldn't see any blue smoke while the engine was idling, so I made the mixture richer (turning counterclock-wise 1/8 turn). However, I noticed that the exhaust was spewing out quit a bit of fuel sitting at idle and still didn't see any blue smoke. I went the other direction in 1/8 increments and it stalls.

Questions are:
1. At idle, should there be smoke?
2. Should there be nitro coming out the exhaust pipe?
3. Is this symptomatic of a lean low speed, or am I running it too rich?


Any help would be appreciated.

Thanks in advance

crash_me_over

My Feedback: (16)

The blue smoke that you are looking for is when you "apply throttle". As the engine builds rpms you then should begin to see blue smoke coming out of the exhaust. That is a sign of an engine running rich....besides the "sound" the engine makes when it is running rich. Set it to lean and it will make a high pitch sound.....set it rich and it will have a burbbling sound to it.

Re-set the needles back to the manuals instructions and start over. FOLLOW THE INSTRUCTIONS for setting it richer or leaner. ALWAYS RUN IT ON THE RICH SIDE......unless you have deep pockets and can afford lots of engines!

Good Luck!

gubbs3

My Feedback: (1)

It sounds like you started out a little too lean. You were right to open up the low end, but you went too far. You don't need to see blue smoke when you're idling. Set the low end so you can idle for about 10 seconds and then have a smooth start when you punch full throttle. If it bogs down and then accelerates away then you're too rich.

speedoo

It sounds to me that your high end mixture is too rich. Which end did you tune first the high or low end? You will have lots of questions here about why this and that about engine tuning and setting. I suggest you read this article which will answer most questions on engine tuning.

http://www.rcnitro.com/rn/articles/super_tune.asp

There are lots of pages here with photos to help you. Just read them all before going full out with your new engine. It will not only explain what to do but why. Excellent stuff.

DT94588

I adjusted the high end needle first and it runs fine at the high end with a nice trail of blue smoke while it runs.

The problem I'm having is that it seems to idle too fast and even opening the carb (turned the idle needle counter clockwise) doesn't seem to slow it down AND it will idle forever if I let it.

The second problem is that when I pull the throttle completely open really fast, then let it go back to idle (I pulse the trigger on the transmitter), the car will stall. Is that a sign of the low end being too lean?

Krusty

You adjust the idle speed with the 'idle stop screw' not the low speed needle. The first needle you adjust is the 'main' needle. It should have a wisp of blue smoke under acceleration. If the engine is idling too fast or slow, use the 'idle stop screw' to adjust the speed. The engine should idle just slow enough to keep the clutch from engaging. DO NOT ADJUST FOR THE SLOWEST SPEED. Now adjust the idle needle so the engine has a nice transition from idle throughout full speed. That's how I usually do it. The instructions you have received should cover these adjustments in more detail. Tuning an engine and needle adjustment has been covered many times in RCCAction. I suggest you look at this and other magazines dedicated to R/C nitro cars.

speedoo

O.K. you seem to be putting the cart before the horse here. If you are breaking in a new engine you have to do it correctly or you are waisting your time and might even damage your engine. There is plenty of information out there on how to do it correctly which it seems you have not read. Here is one of my favorites.

http://www.rc411.com/howto/enginebreak-01.html

It has more than 1 page so be sure to read all of it before you start then print it and follow the instructions. Fire up the engine and go for it. This should answer most of your questions and get you racing fast.

DT94588

I adjusted the Main needle(High speed) first, then adjusted the low speed needle while using the idle stop to try and keep the engine idling while I leaned the low speed.

I wasn't trying to adjust the low end by purely making changes in the idle speed.

Before embarking on this "learning to adjust a nitro engine phase", I broke in the engine per the manufacturer's (Team Losi) recommendations (when through about 6 tanks of fuel driving at very low speed in an oval configuration, varying the speed and not doing any hard accelerations).

By the way, I appreciate all the responses. It's good to have a forum like this where the more experienced folks can help us newbies.

I did go through the linked articles, and was able to get this far. I'm just having a bit of trouble getting the car to not stall when I blip the engine.

flbucsguy

I also just purchased the xxx nt from Losi and I too am having the same problems you are...

Mine will run fine for about 1 lap around an oval and then when I slightly blip the throttle or let out of the throttle from full it stalls...

It is driving me nuts.... I also noticed that I am getting some air in the fuel line to the carb and when the engine stalls the fuel line to the carb partially returns to the tank...

I think part of my problem is that my fuel system is leaking...

not sure.....

DT94588

I took off the air filter and watched the carb.

With throttle at idle, the carb has about a 1mm gap. If I slowly increase the throttle, then bring it back to idle, the carb behaves as it should meaning that the gap remains back at idle.

However, when I blip the throttle quickly, the carb opens up, then closes completely instead of stopping with a 1mm gap.

I readjusted the carb (with air filter off so that I could see inside) so that even when I blip the engine, it will always return and stay open with that small gap.

No more engine flame outs now.

Hope this helps.

flbucsguy

I am glad to hear that you have your problems solved.... It is funny, because I basically did what you did last night and got the car running pretty strong...

However, I now need to replace my fuel tank being it developed a crack in it...

crash_me_over

My Feedback: (16)

Hmmmm.....I have a XXX-NT in the box still needing breaking in. I'm glad you guys posted your problems & results for fixing them.

Thanks!

DT94588

my pain was not in vain! Hope to share more tips and problem solving issues with you XXX-NT owners!

By the way, Happy Holidays!

Tux

I am having similar problems except i cant seem to keep mine idling, where should the setting screws be to break in

shoehead

Everyone says to return to the factory settings to start over.
And also to start with the high speed needle.
But the factory dosnt say where the low speed needle
should be to "start over"
Anyone have a good theory on where to put it?
I usually start with the high speed at 2 1/2 turns.

1fstxnt

2-2.5 high speed 1.5-2 on the low speed

shoehead

Cool Thx!!

code_finger

1fstxnt - is that what you have your Mach .15 set at to start or is that just your standard setup for an engine?

The reason I ask is this- I'm having the same issues all you other guys are having-

But, I didn't have any engine instructions with my XXXNT RTR- so I called losi-

they said 3 on the high end and 3.5 on the low end.

didn't work.

then I found this link- which is the engine instructions from dinamiterc.com: http://www.dianmiterc.com/support
which has the pdf instruction file for the Mach .15

it suggests the settings are 2.5 on the high end and *4.5* on the low end!

Needless to say, at 4.5 the engine was soooo rich the head was locking and the cord couln't even be pulled.

Lame.

So, after a new glow plug and a dry engine, and a few cranks on the low end screw (leaning it out to about 2- 2.5) I started and ran it agian- very rich.

then something really whacky happened.

It started to sort of bog down, (lose power even at full throtle) and then it konked out.

Tuners out there- does it sound like the engine may have warmed up and was too lean on the high end? That's what I suspect.

I also noticed when I got to the truck that there didn't seem to be fuel in the line to the carb- the tank wasn't empty so I'm thinking there may be a fialure in my tank... I always seem to see bubbles in the line when I try to start it that are between 1/8th and 1/4 inch... strange.

Also, I have to hold my thumb over the pipe hole to draw fuel to the carb by pulling the cord a few times- is this normal?

I know this is a ton of info/quesitons, but right now I'm about to light the Mach .15 on fire, film it and upload it here for your viewing pleasure. To say the least, my RC10 electric buggy is a heck of a lot easier to run....

Help appreciated!
Pt

solo racer

I had the same problem with the same motor in the same truck. Ran great at higher rpms, idled for ever, but sometimes stalled out when I let off quick or gassed it to quick.

Leave the high speed needle alone and richen up (counter-clockwise) the low speed needle. Mine now runs like a bat out of hell!

Tux

I had a similar prob with myt xxxnt i found flush on the low and about 2 turns out on the high and set the idle stop to between .5mm and 1mm and that gets you to the ballpark

code_finger

right on! I'll give it a try tonight!
Pt

Tux

Glad I could Help

1fstxnt

code-finger, I always put my low speed at 1.5-2 turns out on the Mach. It seemed to work great for me but, if it doesn't help you than try and keep it flush. Sorry for taking so long to reply but it is cat-fishing heaven here in Ohio. Jon

code_finger

what about on the high end?
Pt

Tux

i dont about 2-2.5 turns out