Reluctant to run

[CH3-NO2]

I've managed to get my Hyper 21 4 port tuned really well now. Over here in the UK, the temperature is around 1 degrees so I'm running it slightly on the rich side to compensate.

I'm having a little problem getting the engine to start running though. It starts up fine, despite the cold and will sit and idle happily. However, the second I open the throttle, even just a blip, the engine stalls.

What I have to do it start it up and let it idle for about a minute. Then very very slightly pinch the throttle open, literally millimeters at a time (sometimes having to just use the trims on the transmitter) and drive it around at very slow walking pace for another minute or so, whilst gradually opening the throttle bit by bit. If I go too much, then engine just stalls.

Once I manage to get to about half throttle, I can let her rip and drive as normal. It's just the initial coaxing that the engine needs.

Is this normal (i.e. due to the cold weather)? If not, any ideas what the problem may be?

Cheers.

 

[Plaidfish]

No it's normal when you run it rich....lean your LSN a lil bit at a time OR check your idle set screw...sounds like you got it right though....LSN is my bet....

 

[CH3-NO2]

LSN is running almost perfect (I think). I've done the pinch test and also tested it by leaving it to idle for 10 seconds, then taking off with WOT and noting it's behaviour.
Doesn't groan, hesitate, or splutter when doing this, so seems like it's fine.

It's weird because surely it would carry on stalling from idle, but it seems once I've managed to feather the throttle and persuade it to rev, it will run fine for the rest of the day - which therefore leads me to think it's a temperature issue... :shrug:

 

[AC48]

It could be the temperature. But I have run a nitro in -14 F and it didn't do that for as long as you describe. It did, but it usually only takes 10-20 seconds or so.

You could try heating it up with a hiar dryer before starting and see if that helps.

 

[Plaidfish]

you're just real rich on the bottom.....if you leave a nitro at idle they will load up...if it doesn't then you're running real lean on the bottom......that can be bad at a certain point.....keep in mind when you tune an engine it's not "DONE" like it stays tuned forever....a stiff breeze of cool air can lean bog these little things....seen it happen and 4 buggies all just cut out in the middle of a race......funny as hell if you weren't one of the guys scrambling to get it back on the track......did the engine start to rev after 3 seconds when you pinched it?
I run mine real rich on the LSN so I have to keep revving it when it's idling or it cuts out....when I race I'll retune it just before the second heat and that's usually where it stays for the main too.....

 

[CH3-NO2]

Yeah, they're never tuned to the point where you can just leave them, since as you suggest, changes in air density, temperature, humitity etc etc all seem to have a substantial impact on these tiny engines. However, saying that, I seem to have it setup right for the current conditions that I'm running it in, obviously with a few minor tweaks depending on the day.

After pinching it, the engine revs go up a little bit after 3 ish seconds for about 10 ish seconds, then cuts out. Is this correct?

The take off seems to be the one that feeds back to me the most information. After leaving it to idle for a while, it takes off very cleanly to peak RPM, where it appears to clean out nicely. However, it doesn't load up if I leave it to idle. Are they suppost to stall after a while of leaving to idle? When running the engine in, I had the engine running as rich as it would possibly go, and it managed to idle for full tanks of fuel.

Thanks for the tips, guys!

 

[evan811]

I had the same problem, but it was on the starter box, so I gradually gave it more throttle, but it only took maybe 20 seconds, I always figured it was the WD-40 burning off in the 1st couple seconds of run time...I also to run very rich....

 

[Plaidfish]

that's weird that it will rev up for 13 seconds when you pinch it...I think I run rich and it stall after a 5-6 second pinch.....I see guys tuning their stuff to idle all day long but when you think about it you DON'T want that....are you driving or idling all day.....I never care how long mine can idle cause they don't stay still for very long ......I start mine up and set the idle up a lil bit til the temp gets over 140, then I start revving it slow to get it up to temp.....after that it doesn't stay still unless it flips and if you don't rev the crap out of it while it's upside down it should run for a while......I actually hit my brakes and just do 2 or 3 blips when it's on it's lid, if I can't flip it by the 3rd blip I just leave it and let it die.....

 

[CH3-NO2]

Managed to get this sorted out now. Turns out it was running a little rich at bottom end, so I leaned it out slightly and it's fine now. Still requires me to leave it for about 10 seconds on fast idle (using the trim on the transmitter) but then after that, I can drive as normal, without it stalling. So I just leave it on fast tick-over while I put the shell on and that's sufficient.

Thanks for the suggestions, guys.