Inferno Engine Stalling - HELP!!!!!!!

[Paullanzarotti]

Please please help! I am new to Nitro RC and just purchased a MP7.5 RTR.

RTR my ass!?! I have had an absolute nightmare with this beast of a car. I have taken it back to the shop who "tuned it" but it's still not running right. I have broken it in finally (couldn't get engine to run for longer than 2 minutes for 3 days?!?) but still the engine is an absolute pig.

It's hunts, if it approaches low revs it cuts out. the revs are set as high as possible now before the clutch engages but when I bring the car to a halt it stalls. Not all the time but roughly every 5 minutes. I have never managed to run a tank of full down without the engine dying and then re-starting can be a nightmare.

I have changed glowplugs, I have changed fuel to a high quality 20% and still the problem persists. My fingers are literally bloodied and blistered from trying constant restarting and I have never managed to run with the body on I'm constantly trying to tune.

Please help! I'm on the brink of giving up and I dreamt last night I swapped it for and electric buggy!?! (Ok - I'm losing it now) I just want it to run without stalling. I've set the high revs needle ok - and the idle is at max. The grey area is the low rev needle. I have kept it close to the setting the guy in the shop made - but it's not working. What do I do next apart from get a new engine??

 

[uDi_MP7.5]

Try screwing what the lhs guy told you, and reset the engines needles to default factory settings. There should be a book or manual that came with the kit that lets you know what those are.

Before you get into engine tuning, make sure everything else is set right. Your idle stop screw should be set to limit the min. carb opening size to 0.5-1mm. You need to make sure your servo keeps it held at the "closed" position at idle, and that it opens it fully at max throttle. This might take some time playing with the trims and servo horn position on the servo since the stock radio doesn't have EPA, but you'll get it eventually. I've got a gut feeling that maybe when you brake your carb is closing more than it is at idle. That would cause it to cut out. Take the airfilter off and note the carb opening, when you go from idle (neutral) to brake with the radio, the carb slide should stay put.

Once that is all set, then fire her up with the factory settings, see how it goes. Assuming it actually runs to some extent...:

It should be blowing a little puff of blue smoke when you accelerate, and there should be a light trail of blue smoke when you are doing some high speed passes.

If there is a LOT of blue smoke on acceleration, and some bogging/hesitation, your lowend needle is too rich, lean it out 1/8 a turn at a time until it accelerates cleaner.

If there isn't much blue smoke on accel, richen up the lowend needle 1/8 a turn at a time.

Once again for the top end, if there is a heavy trail of smoke, just lean it out 1/8 a turn at a time until there is a light to moderate trail.

And if you can barely see smoke, richen up the topend 1/8 a turn at a time until you do.

That's the good old tune by smoke method. Works a charm for me.

i'm not too sure exactly how new to nitro you are, so i'll add some other stuff just in case. Leaning out a needle means closing it (clockwise) and richening it means opening it (anticlockwise). Smoke coming from the exhaust indicates that the engine is being kept well lubricated (running rich), so that's why that's important. Too rich (too much smoke) and it will run sluggish and loose performance so there will be a fine line thats a good compromise between both.

Hope that helps in some way?? Or maybe I am totally off track.
-uDi

--edited--

 

[dgrobe2112]

Right.. ok.. here is what you do.. there is 2 needles on this motor.. the high end.. sticks up next to the air filter.. and the low end.. should be on the side.. where the throttle servo pulls on the carb. or on the opposite side..

First thing.. if you got a new glow plug.. put it in.. then.. screw the high end needle all the way in.. gently.. dont over tighten it.. after than.. you wanna turn it out 3.5 complete turns.. that is 360 degrees..

same thing on the low end.. screw it in.. then screw it o ut 4 complete turns.

This should get you back to close to where you were when you got it.

pull your air filter off..turn on the switch to activate the servos.. pull your throttle just to see what is moving in there.. you will see the slide valve of the carb.. notice the ( in the end of it.. now.. let off the gas.. and let the servos recenter themselves.. you will notice the ( is almost closed.. you should be able to still see some of the opening.. if not.. turn your idle set screw.. this screw is located on the carb.. same side as the high speed needle.. on the side.. can't see it.. except when you look at the car sideways.. screw it.. till you see about a 1mm opening..

then your set.. put your air filter back on.. start the car.. you dont need the body on the car at this time.. until you get the thing to run a full tank..start it.. it should sit there and idle.. if not..

1. turn your low end needle 1/8-1/4 turn... clockwise.. like tightening a screw.. restart it.. give it some gas.. by blipping the throttle.. see if it will idle after that.. if not...

2. turn up the idle just a little.. you may want to adjust this with the engine running.. i set mine.. when the engine is running.. and i am holding full brake..

by now.. you should have this thing sitting there idling.. at least.. next..

while its sitting there.. pinch the fuel line that goes into the carb.. pinch it closed.. the motor should idle for 2-3 seconds.. before you notice it change note.. if it changes faster than 2-3 seconds.. then turn your low end needle (on the side of the carb.. counterclockwise.. 1/8 of a turn.. then.. give it some gas.. if it sits there and idles for more than 3 seconds.. you can lean.. or turn your low end needle.. 1/8th turn clock wise.. then give it some gas.. then repeat the process until you get it to be around 2 seconds..

go ahead and run it down the street.. or down your driveway.. dont go full throttle yet.. just see if it will run.. if so.. gradually start to speed up.. you will notice the motor want to go fast.. or be blurbing.. like gargling sounding.. if that is the case..

1. turn your High speed needle.. the one that sticks up from the carb.. 1/12 of a turn.. that is 1 hour on a clock.. just a hair.. not a full turn.. then run it down the driveway again.. and see how it responds.. keep repeating this process until you get the car to clear out.. and go faster.. make sure you got smoke coming out of your pipe..

 

[Paullanzarotti]

Great advice!

Thanks guys for getting back to me so quickly. The funny thing is a can build, tune and max out VW engines from scratch - so I kinda figured tiny little Nitros would be a walk in the park.

I was half right. I've been running across my local park with a glow start in hand for 3 days!

Seriously though - the instructions with this thing are so bad it actually quite amusing. Obviously English translators are thin on the ground in Japan?!

The "instructions" also say no more than 2-2.5 full turns on the top valve - yet you suggest 3.5?? Shall I ignore the instructions full stop?

I will take your advice with me to the park tonight and see if where I can get to.

What I have found suprising is how eratic the engine is. If there was a pattern of behaviour I might stand a chance but it really dos seem very, very random which makes it hard to get to the bottom of the problem.

I will reset everything and start again and report back.

Thanks again.

 

[dgrobe2112]

well 3.5 is a almost sorta standard i guess.. if i am working on someones buggy.. helping tune.. or soemthing.. that is where i start.. taht way i am not too lean.. if your too fat.. you will know it.. and you can work in from there.. but if you drive the buggy too lean.. then its hard to sneak up on the tune.. go with what the book says.. i dont know if those setting are for going.. or for breaking in.. but go with what your manual says.. and make sure to let us know how it goes..

 

[uDi_MP7.5]

Dude tuning needles are different for all engines. The way the needle is made, the taper, the thread pitch, bla bla.

So a "standard" never works, there's always a default setting for each engine.

Paul - i'd stick to what the book says - if 2 - 2.5 is what it says for topend, use that, and work from there.

 

[Nitro_Freak]

umm, uDi, i think you made a couple mistakes about which way to turn the needles... clockwise means leaner, counter clockwise means richer. i've done it like this on all my rc's, they all run good......

 

[dgrobe2112]

i'm not too sure exactly how new to nitro you are, so i'll add some other stuff just in case. Leaning out a needle means opening it (counter-clockwise) and richening it means closing it (clockwise). Smoke coming from the exhaust indicates that the engine is being kept well lubricated (running rich), so that's why that's important. Too rich (too much smoke) and it will run sluggish and loose performance so there will be a fine line thats a good compromise between both.

Hope that helps in some way?? Or maybe I am totally off track.
-uDi

yeah.. your right.. lean the motor means turn the needle clockwise.. and fat the motor means turn it counter clockwise..

 

[uDi_MP7.5]

sorry my mistake. *blush* it was like 2am over here that day i was typing that and i looked at the clock to work it out and i obviously did a pretty poor job.

Leaning = clockwise (closing)
Richening = anticlockwise (opening)