My First Nitro - Having Engine Starting & Idling Issues

[SethWillits]

Howdy - So I got this HPI RS4 Nitro (RTR) sometime back and tried breaking it in, something came up and it got boxed for too long. After just moving, I decided to try it again, so I got it out today and the memories came rushing back in. The friggin' thing is difficult to start and keep running!

Starting I have more or less figured out, but when trying to leave the thing at idle/low speed to break it in like the manual says, one of two things will happen. Either it will a) hum along nicely and then just go randomly go nuts at near full throttle, or b) hum along nicely and then just start to starve and die. Trying to break it in by running at idle for three thanks is extremely difficult when I can't get it to run on its own for more than a minute with out having to slow it down or speed it up, and restart it after it dies.

The manual isn't exactly helpful for either of these problems. I've tried adjust a few things, but nothing seems to make any difference. I'm at a loss of what to do. Any suggestions?

Thanks :thumbsup:

 

[TeamLosiNXT]

Recheck your mixture screws. Low speed and high speed. I know mine was sitting from when i was 9yrs old to now and I'm 21. And I had to dissamble the carb and clean it out. The fuel gummed it up. Try spraying carb clean and compressed air to blow the passages clean. What motor is in it? Also check for air leaks. See if your fuel lines are ok, and check your gas tank.

 

[HeartBreak]

Could be a clogged carb, or most likely, gummed up fuel lines. If it's the fuel lines, it'll cost all of about $2 or so to replace the lines. If the engine itself is gummed up, there's really not much you can do, aside from tearing it down and cleaning it thoroughly.

 

[SethWillits]

It's not the fuel lines or an air leak - checked that. The tank is fine. The behavior I'm seeing now is exactly what happened when I first got the car so it's not a wear or gumming issue.

The motor is a Nitro Start T-15, using factory fuel.

I'm pretty sure it's running really lean as it doesn't have the characteristic smell and smoke of burning rich, but adjusting the needle on the carb doesn't seem to be helping (which is odd). Adjusting either way more than a half turn just kills the motor fairly quickly.

 

[HeartBreak]

How much fuel do you have through the engine so far? If it's fairly new, it could be that its' still too tight.

 

[BOUTCH]

:whistle: Idle screw maybe?

 

[SethWillits]

How much fuel do you have through the engine so far? If it's fairly new, it could be that its' still too tight.

I'm pretty sure at least a tank, maybe more. Not very much.

BOUTCH - it's not the idle screw. I already checked that

 

[HeartBreak]

If you've only got about a tank through it, it's likely the engine is still so new it's pretty tight. It usually takes at least 4 or 5 tanks before the engine shows signs of behaving. Stick with it, it'll come around.

 

[SethWillits]

So I played with it some more and was adjusting the low end carb adjustment which is barely even mentioned in the manual for my particular model, but is talked about more in a later model, so I have it burning nice and rich on the low end and it was doing pretty well for about a minute, then started climbing in RPM rapidly again.

In order to slow it down all I did was brake, and then it would start climbing again. One time, however, I noticed that when I used the throttle instead of the brake, it also dropped in revs significantly, then sputtered and died after about 10 seconds. As soon as it died, I could hear what I thought was something boiling but was just air bubbles being sucked in from the carb into the fuel line between it and the tank.

Interesting.

 

[HeartBreak]

Sounds like you have a hole in one of your fuel lines. It doesn't take much to let a lot of air in.

 

[SethWillits]

I got another tank through. I found a nice spot where it seems to work nicely, but it's burning too rich I think. there's a pretty fair amount of fuel sputtering out of the exhaust, and quite a bit pours out when I tilt it over. The smoke is also a bit more than "a little." However, when I lean it out is when I get the racing RPM climb. Shoving more fuel into it by giving it a healthy stab of throttle brings it under control. So I'm in a paradox. It's too rich, but leaning it out is too lean. Bah

I'll keep trying and get another two tanks or so through and see if it's getting any better. Haven't seen any air leaks yet. I think what happened last time is that the motor overheated so much that it just expanded the fuel line so it started sucking air in when it shut off. It was pretty hot before, now it isn't so much.

 

[jon2]

Ok I can offer three suggestions,

First the glow plug. Its not uncommon for these to get fouled up especially when sitting for a while.

Second, That " racing RPM Climb" sounds like an air leak. I know others have suggested it but have you tried to seal your engine up? Let us know on this one.

Last, your clutch. Does your car idle and seem to roll away even though its at idle? This can be caused by a faulty clutch spring causing the clutch to engage early.

Let us know what you find.

Jon

 

[bourney2006]

forst of all sorry i havn't read all messages so sorry if i repeat anything already said.

Right number one on your list sounds like a radio gear problem, you may be getting interference from somewhere, you should already have a failsafe fitted but if not go and buy one before you do anything else.
Set your carb back to factory settings (if these settings arn't in your manual look on google). Then when you have set the carb back to factory sttings turn the end point on your servo up very slightly and richen up the top end 1/8 turn until it stops cutting out, but not too far or it will load up and cut out. If starting is a problem again carb settings and end points could be to blame, or you could try replacing the glow plug. When you start the car if it cu's out as soon s you take the clow start off the glow plug then you need a new glow plug.


Also try a heat cycle run-in, this is an excellent run-in method, just don't be too mad on the throttle. There should be a sticky on heat cycle break-in's in one of the sections of this forum, it think it's the engine section





EDIT: i looked on google for factory settings but as you didn't state the engine i had a bit of trouble (as the rs4 apparently comes in two versions with two differnt engines, the fr15 and the .18 but i couldn't find settings for either.
My advice is if you can't find the setting's then 3-turns out on the high speed needle, and 1.5-2 turns out on the low speed needle sounds good to me

To set your carb to these settings screw HSN (high speed needle) and LSN (low speed needle) all the way in (but dont screw them down too tight or you will crush then end's and wreck them) Then screw the HSN out 3 turns and the LSN 1.5-2 turns.
Then start it. Mess with end points to keep it running but don't llow it to rev too high




just read jon2's post. He may have a point about the air leak. Does it get extremly hot even at idle? if so ou have an air leak. Also to check if its the clutch start it and even if it seems to rev low but is sill moving then it probably is your clutch. Take it off the box and drop it on the floor if it immediatly cuts out then it's definitly your clutch.
Take your clutch bell off and fix it (if you know how) if not just ask on here