bicyclebob

hey guys, just took my caldera out to try and break in the engine and ran into a problem. when i start the engine, the engine revs at such a high speed i guess that the wheels spin. However, looking at the carb opening, it is just about a 1mm open, so i'm not sure how this could be. i tried turning the idle screw down to close the opening, but the engine just died. also, after a few minutes of running, the engine would rev real high and quit. any ideas or suggestions. keep in mind this is a brand new truck and engine. thanks.

nitrosportsandrunner

were the wheels off the ground?
if there is no resistance on the wheels, then the clutch will grab and spin the tires...and this will also allow the motor to rev higher.
remember, even tho the carb opening is small, the high speed needle is set way open. this is to lube the motor well durning breakin, but also can allow the motor to rev high in the beginning.

you should have the truck on the ground. it may want to move forward, but it should only take light effort with your hand to stop it. if thats the case, then just put a block in front of it.

after the 1st tank, let the truck putt around in a circle or figure "8". no punching the throttle or slamming the brake. just rolling around slowly till the tank is gone.

also, during the breakin tanks its normal for the idle to raise toward the end of the tank. has to do with temps raising and the low tank pressure lowering the fuel going to the motor.

bicyclebob

okay, that sounds good, i will put the truck on the ground next time with a block in front of it. the car doesn't die toward the end of the tank, it just revs up after a minute or two and then dies. would the gear mesh have anything to do with this?

nitrosportsandrunner

nope.
the rev up a couple mins before dying is do to the lower pressure in the tank.

the term "mid tank lean" applies.

its common in most nitros that when the tank level drops below half, the amount of fuel that goes to the motor decreases a bit.

bicyclebob

the reving up was actualy going on during the entire tank. is there anything i can do for the low pressure in the tank?

bicyclebob

okay, i think i just figured out the problem. i have the high speed needle set 4 1/2 times out (counterclockwise) from closed, and the book says that it should be around 2 1/2, but it also says at another part of the book 4 1/2. i checked the temp and it was running around 150 degrees F while running, so i'm assuming that is my problem, it is running too rich.

nitrosportsandrunner

OK, i know its confusing. redcat does need to work on their manuals

put your high speed @ 4 turns out from closed. it is supposed to run very rich during breaking.
the fuel contains the oil needed to help cool the motor.
each tank that you run, you will lean out the high speed 1/2 turn.(thus you will end up around 2-2&1/2 turns out when done with breakin)
thus, with each tank the motor temps will rise.
by tank # 4 you should see temps 200-240
then its safe to tune for max performance.

dont focus on the high idle. there is now point in messing with the idle till beakin is almost done.
each time you lean out the high speed 1/2 turn, the idle may raise slightly.

bicyclebob

okay, so the high idle isn't a bad thing, but having it idle fast will cause the wheels to spin, correct? when i had it idling up on a block with the wheels spinning, i grabbed one of the wheels to stop it and the car died. also, why would the car all of a sudden, when the tank is full, rev up real high and then die? i just got through my first tank and it died probably 5 times or more.

nitrosportsandrunner

it takes patience my friend. i had a backdraft 3.5 and it was the same way. the 1st couple of tanks were a pain. had to starte the motor many times.

breakin is a real pain. youll start that motor so many times during breaking youll get a blister on your finger.

once a motor is broken in, and the carb is tuned it will be a much easier thing.

just start running a tank at a time with the truck slowly putting around in a parking lot or your driveway(flat surface)
its not nessesary to have the truck held in place after the 1st tank

after each tank, let the motor cool. then lean out the high speed and repeat.

with each tank, the motor will stay running easier and have more power.

bicyclebob

okay, hey i appreciate it man. sorry if i sounded a little frustrated, i just didn't expect the difficulty of the break-in period. i should have, after all that i have read, but its different when you can't wait to get that truck out on the track. again, thanks for all the help.

nitrosportsandrunner

no problem. MANY new to nitros get frustrated.

its a steep learning curve with nitros.

kelynsdad1023

also just to add during break-in you want to get the engine temp up to 200 degrees.....so pre-heating it with a heat gun or hair dryer helps to do that and it will start much easier.

bicyclebob

alright, thanks for the info about heating up the engine.

bicyclebob

okay, so i got 4 full tanks through the break-in process and it is starting up easier and i guess it is running stronger. however, i'm still having the problem where it revs up high enough in idle that the wheels move. i have yet to really mess too much with the idle screw since the 2nd tank, so i'm going to mess with it on tank 5 and see if i can get it tuned right. any other suggestions as to why this could be happening?

nitrosportsandrunner

with 4 tanks threw it its safe to adjust the idle set screw.
it natural for the idle to raise as you have been leaning out the fuel mixture with each tank.
what temp has the motor reached?

after tank # 5 you want to be about 2-2&1/2 out on the high speed.
then you can adjust the low speed.
to do this, just run the truck up and down the street(or parking lot) and lean out the mixture till the model takes off without bogging. then richen it 1/4 turn(its always best to run a tad rich)
now adjust the idle again if nessesary.
motor should be tuned for optimum now.

if you havent yet, check out the vids on this page: http://www.redcatracing.com/informat...otraining.html

bicyclebob

okay, sounds good, i appreciate all the help man. i will mess with the idle screw tonight and see what i can do. and most of the information i have has actually come from those videos, but thanks anyway. i'll let you know what happens.

iluvny081

I dont pretent to know everything about nitro but i wouldnt rule out the possibillity that you have a leak somether, an air leak that is. most comonly air leaks come from the plate on the rear of the motor that the recoil mounts to, a pin hole in your fuel line, an air leak in your fuel tank, a crank bearing that has a bad seal and lets air in, a warped cooling head, or a poorly sealed carborater, not saying thats definitely the problem, but you should perform some leak testes to rule it out because when you have a leak it will make the engine run really weird. if you dont know how to look for leaks go on youtube and look up nitro video's by a guy named "squirrel" they should teach you everything you need to know to get your truck running right and keep it running right. I hope this helps.

bicyclebob

okay, i watched some videos by that squirrel guy on youtube and he actually suggest adjusting the throttle servo arm. i'm really hoping that it is simply a problem with the idle screw and low speed screw adjustment, because i really don't know much about these trucks.

bicyclebob

okay, so no luck finding what the problem is, so i'm taking the truck to my local hobby shock and hopefully they can figure out what the problem is.

bicyclebob

okay, so no luck with the shop i took my truck to. apparently they don't work on redcats! i mean c'mon! all i need is a little professional help and nobody is there when you need them!

nitrosportsandrunner

my LHS is the same way! they dont want to mess with anything they dont sell. thats not a way to instill customer loyalty!

in fact, they wont tune nitros anymore either.

if i ran a shop, i would help out anyone i could, no matter what model they had. and i would do my best to tune any nitro. no harm in trying!

kelynsdad1023

tell you what if you wanna ship the truck to me I'll take a look at it for you and tune it !

bicyclebob

hey, i will definately consider shipping my truck to you to see what you can do. i actually got the engine out of the truck, but in the process i stripped all four heads for the engine mount (not sure if they are crappy screws or my allen wrenches are bad), so i drilled the heads off and finally got the engine out. i'm going to go back to my LHS and see if they will just mess with the engine. i mean, how different could a redcat engine be to a traxxas!? if i don't have any luck there, i will definately consider seeking your help.

Yeah, i'm not sure what the guys problem was i talked to. i think he was working on his own truck when i went in, and his associate called him over to help me, so he was probably alittle upset he had to stop work on his own truck. but hopefully i can talk to someone else this time and maybe get something worked out, because i definately got this thing to drive it, not work on it! wish me luck!

rchobbyunlimited

It difently sound like an air leak since you already have the motor out take off your backplate and seal around the entire backplate with hi temp silcone then remove your cab and seal also. Put zip ties around all ends of the the fuel lines on the engine and the tank. This should fix the problem. Is there bubles in your line when you are running? if so the bubbles is whats causing the engine to lean out and thefore rev high and turn you wheels.

bicyclebob

there are a few bubbles here and there when i first try starting the engine, but when i get the engine running there aren't any bubbles.