asg_crew1

Hi im new to nitro cars and I just got a used rustler. Its had about 15 tanks total through it. It was runing good when Igot it then I started ****in with it now its all outa wack. The problem is the engine keeps cutting out after I give it gas and the rpms start to come down. It seems to bog down some at low speeds to. It idles fine maybe a little varation in speed. It seems like when the RPMs are going down it drops real low and sometimes comes back up to idle speed other times it will cut out. I have tried tuning the high speed needle untill Ifelt it was at peak performance then tuning the low speed. Ihave tried the pinch test and it cuts out after a few sec but doesnt speed up before it does. I have also turned the idle up without any luck.Ichanged the carb settings to stock and tried all over again but im geting basicly the same problem of it cuting out after Ilet off the gas. Also Iseem to be able to find a sweet spot every now and then where it runs decent and will wheele but then as it keeps going it will start to cut out again. The low speed needle doesnt seem to be moving on its own but Icould be wrong. There are no air leaks that Ican find and the intake and exhaust are on tight.Thereis a little bit of gas coming from the exhaust.Any help would be greatly apreciated iv been trying to tune this damn thing for two solid days.

CarGuy7a

Usually when I EFF my tuning up I'll go back to factory settings. HSN 4 turns out from closed and LSN Flush with the housing.

I usually start with the LSN I know it may sound backwards but try it once. I do it to mine everytime and I usually get a great tune when I do it. The Pinch Test is only used as a guidline. Mine likes to run with a Pinch Test of about 4 to 6 seconds.

Set back to factory first before doing this.
What you wanna do is take off your air filter assembly off the carb and unscrew the idle screw until the slide fully closes. Ok now screw the idle screw back in until you see the slide move just a little bit. Now re install the filter assembly. Your motor should Idle very high when you start it (at least that's what mine does when set back to factory) Ok now start richening the LSN until the RPM's become stable and do not Increase and Decrease rapidly. Sometimes if you go a little too rich it will stall, if it does lean it out about an 1/8th turn or so then fire it up. You may have to hold onto the truck and give it full throttle for a second just to clear the built up fuel and then continue LSN tuning. The point of this is to try and get a good stable idle without having to use the idle adjustment. Now by this time the engine should be at operating temps around 200 degrees F. Run the Truck around a few passes and check the pinch if it's under 3 seconds richen the LSN if it's over 3 seconds by not much maybe 4 seconds or so and runs good without stalling leave it alone and go to your HSN settings.

Usually when you have a Lean LSN when you let off the gas from full throttle the RPM's will stay up there and take a few seconds to drop. What you want it to do is pretty much drop to idle when you let off.

Chris_RC

Also, what happen to my engine was the LSN was too rich and it did the same thing as LSN too lean. I got a pro to tune it and havent even touched the needles in a couple weeks. This is what he does: Start leaning LSN, then counteract the idle by lowering the idle. Do this until the engine revs up slightly and dies within 4-5 seconds. Now you have your LSN and idle perfectly tuned, you now tune your HSN. Before you tune that, richen LSN 1/8-1/4 turn depending on how lean or rich the HSN was before (if it was at race tune, rich lsn 1/8, if at factory richen about 1/4) I do this because when you lean the HSN you also lean the LSN. Now you can bascially call your temps and performance from the HSN. Once you got your engine running great with a "fair or small" arount of smoke, check temp. Engine should be around 200-250. If lower, lean HSN and if higher, stop engine and richen HSN. If the engine is in between 200-250, recheck LSN with the pinch test-let idle for 15 seconds then pinch it, engine should rev up slightly then die in 4-5 seconds. Your engine should idle low, tires shouldnt spin if your tires are off the ground (well they could spin slowly but I would decreasew the idle a bit more). NOW you have a perfectly tuned engine. After that, you really shouldnt have to tune your LSN and idle much unless of big temperature or humidity changes. This way has worked out the best for me, rather than the HSN first, then LSN, then idle. That method never really made sense to me for some reason.

CarGuy7a

Exactly. Everytime I've tried doing the HSN first my temps usually get jacked up in the 300's then I have to sit and wait for it to cool down before I can continue. It's always made more sense to me alsoto tune from the Low end (LSN)to the Top end (HSN).

Everyone has a different "Method" of tuning. You just have to find one that's easiest and quickest for you to do. Once I get mine set I usually only have to move the needles a max of 1/8th turn from one day to the other. Of course when you switch fuel brands you also need to re tune. I found that out when I went from Traxxas Fuel to Wildcat. I had to richen it way up for the Wildcat.

fasty

check your clutch spring it might be broke

MCSRacing

My Feedback: (2)

lol i tune both needles at the same time .... works for me i guess, i always get a good tune that runs 210 or so if the motor is good to go

rustler1882

I've have the same problem with my 2.5 nitro rusty, also mine is running very rich and still the engine gets super hot! I'm lost - people were saying maybe there's an air leak in the engine somewhere and to seal it but then it voids any warranty

Chris_RC

You want the engine to actually run right? Then seal it up. How in the world would it void warranty for a common practice? Oh, I know-some newbie knows nothing about cars and see sealing engine videos and uses homemade silicone and destroys the engine but if yuo do it right don't worry about it.

rustler1882

I'm not really sure the detais, was just told by the hobby store owner, ya i'd obviously rather the engine run right... never done it before tho - best method to use, best sealant?? I wonder whyt they dont have gaskets... it would make sense in sealing the engine. Do you think thats my problem tho - from what it sounds?

CarGuy7a

Any kind of air leak will make an engine run hot whether you are on the rich side or not. Even a minor leak can cause it to do this. On my Slayer I've had the fuel tank O Ring leak a miniscule amount and it made the temps hit the 300's. Fixed that little minor leak and it didn't overheat anymore. These motors are so small it doesn't take much of a leak to make em cook.

I've not had any leaks in the 3.3 motor itself but that's just my motor and I can't speak for the millions of them out there. If I absolutely had to I would seal it up with RTV and if you ever needed to send it back clean it up real good and get all the RTV off before you send it in. What they don't know won't hurt them.

Chris_RC

Get Lucky 7 sealent instead. RTV is NOT Nitroproof.

MCSRacing

My Feedback: (2)

yamabond works great we use it on nitro burning banshee engines .. its the best out there i have found .. i havnt tried lucky 7 but i will tho

Chris_RC

Put RTV in a cup of nitro. Get up the next morning and it WILL deterioate. I also use Associated Green Slime to seal the tuning needle o rings(idle, HSN, and LSN).

rustler1882

K cool thanks guys, I saw an awesome link in another thread to RC Hobby's Online - for car engine tuning and set up that gave a great tutorial on how to find air leaks so I'm going to go through the whole process tonight and see what I can find. the link is www.*********.org/engine-tuning.htm