4-tec with 1.5 pro giving huge problems.

[Bigpapasmith]

Hello guys I am realativley new to the hobbie but I understand the basics. I rebuilt a 15 year old RC10 and got it running fine then upgraded to a bigger better engine and am still running it and having fun. I recently got a traxis 4-tec with a pro 1.5 in it. The guy I got it from had the carb all screwed up and could only get it to run when he squirted gas in the carb. He gave it to me and I retuned the carb and was able to get it to start with no problems and even drive it at about 2 miles an hour. If you leave the throttle open just a bit it will sit and run through a whole tank of gas but if you try to give it more than just 10% throttle it just shots off. It doesn't make any noises it doesn't bog down it just stops. I tried tunning the needles both ways and got no results. I figured the enginge was jsut worn out. I bought a new piston and sleve and new gaskets for the exhaust and head. I also bought all new o-rings for the carb. I tore the hole engine apart and rebuit it with the new parts and inspected everything, nothing seemed wrong. I readjusted the carb back to factory settings for break in and fired it up. It started right up and I let it idle for a few seconds and then tried to drive it and I am having the same problem. It just shuts off. I know its not the needles Low or High speed settings becuase when I adjust them all I manage to do is make the engine idle worse. I also did the pinch the fuel line technique and it idles fine and then revs up a little and dies if I dont un-pinch the line. Its tuned right. I jsut dont know what else to do. Also before you ask I removed the spur gear's so that the engine was running free. I know that is normaly a bad Idea but I wanted to make sure that the transmission wasn't the cause. With nothing hooked to the engine I still can't get past 10% throttle without is just shutting off. I dont think it is an Air leak because my RC10Gt had one and it cause wierd hickups in idle and acceration. This car idles fine it just doesn't like to go. Somone please give me some Ideas or sugestions. If you can get me to get it running I send you a video of me blowing it up as I red line to take out my frustrations.

 

[nitroghost]

Go get a trx 3.3 and put it in the 4-tec. I dont think the pro 15 are even worth building anymore. I have a 3.3 on mine and man does it move!!

 

[brad55102]

I am going to have to agree!! get rid of that .15 and get a 3.3 your going to be much happier in the end. If it is a money issue then set the carb to the original settings. Whatever you do dont rebuild the engine. A new sleeve and piston will cost you $50 and will probably still give you problems. A new 3.3 will cost you $100 and run great.

 

[Scrogg]

Those pro .15 's can be mofos, I had one in my first nitro. Damn near made me cry trying to get it to run.
From what you described somethin in the engine is slightly binding. Did you replace the engine bearings when you rebuilt it? Also check that the OWB is not locked down on the starter shaft. Look for things of that nature.

 

[Bigpapasmith]

I put the factory settings on the carb back to default and I allready replaced the sleeve and piston. I know that needed to be done anyway because I could turn the motor over with out hardly any pressure at all. Once I replaced the sleeve and piston, Which only cost 35 bucks, there was a ton more compression. Also I called traxxas because I thought that maybe it was a bearing in the crank as well. But traxxas told me that if it starts and idles as easily as it does than its not a bearing. They told me that it has to be a fuel problem. He says that my Carb is not getting enough fuel, and that if I have the carb set right then it has to be a clog in the tank or I am not getting enought back pressure off my tuned pipe. I checked both things. The tuned pipe and it is not clogged at all. I can blow right through it. And if I blow on one end of the gas tank then gas freely poors out of the other end so I know its not the gas tank. I also slightly submerged the car in water and pressurised the whole system and the only place that I saw bubbles was out of the low speed needle assembly. I checked with my other car that runs great and I noticed that under water and pressure it boubles in the same place, so I am assuming that that is normal. So I just dont know what to do. Someone help me. Without telling me to buy a new engine. I could figure that one out by my self.
Sorry for the long winded reply.
Thanks

 

[Scrogg]

Bubbles from the LSN is a big problem. Replace the O-rings, and grease them before you install them.

 

[Bigpapasmith]

the o rings on the carb were replaced, all of them. And the low speed doesn't bubble when it running just when I submerge it under water and plug all the open wholes and pressurerise the system by blowing through the fuel tubbing. I was checking for air leeks. My Other engine a .18 cv-r from O.s. is brand new and runs great and did the same thing when I tested it to make sure it was normal. And it not exaclty the lsn its the rubber boot that goes around the throttle arm the the low speed needle screws into, is where the bubbles came from and I had to blow really, really hard to get them.

Is it possible sense the piston and sleeve are brand new its just a little tight. Maybe I should just let it iddle for a few tanks of gas and see if it loosesns up a little. I noticed with the head off, if I try to turn the engine over and I am pressing really ahrd on the sleave it still wants to push the sleave up a few mm right before TDC, I think the sleve is slightly tapered or something at the top. Maybe its just getting stuck when I try to go fast. I dont know. All I know is its getting me upset. It starts and Idles fine. I just can't give it gass or it just shuts off. I checked and thier is no fule blockage or air leaks. And traxxas tch support said that if it was a bearing in the crank then it wouldnt idle and besides the I checked the bearings last night they seem fine. I thinks its time for some C4 and a pull rope. I am gonnas tow it behind my RC10 GT and blow it up going down the road.

 

[Rolex]

One thing I found while reading this thread is that there is NO mention of a break in. When an engine is new, what needs to break in is the fit between the piston and sleeve. Your engine is old, but your piston and sleeve are new...=another break in. It needs to be treated like it just came out of the box.
If you can start it and idle it, then do that for a tank or two with the needles at factory settings. You might need to richen the LSN since it cuts out as soon as you give it any throttle. Once you can accelerate and run it slowly for the break in, follow the recommendations in your manual.

 

[Scrogg]

I totally agree with Rolex. The engine is no where near broken in from your lost post's description.
Preheat the engine before you start it. This does wonders for easing the break-in process. A hair dryer will get you to 150F which is good enough but if you have access to a heat gun you can get it to 200F which is golden.

 

[olds97_lss]

I also didn't see any mention of you trying a new glow plug. When glow plugs sit for a period of time after being used, the coating on the coil gets eaten away by the acidic environment inside the engine (fuel/exhaust/fire = bad). When glow plugs start dieing, you will be able to start an engine with the heater on the plug, but as soon as you take the heater off, it dies. Or, as soon as you apply throttle from an idle, it dies.

If you leave the heater on and apply gas, it more than likely won't die.

First, read the above posts and do a break-in process. Until this is done, it needs to be tuned a bit rich. If, after 4-5 tanks your still having the issue, then let us know.

Before you start the break-in, get a new glow plug if the one in the engine is old.

 

[Bigpapasmith]

That seems to be working. I didnt have a manual for this car since I got it off a friend. And I was following the break in specs for my O.S. .18CV-R and that engine ran right out of the box. I have now run 2 tanks of gass at idle through this engine and it is getting much better. I can give it more gas now before is stalls. I think in another 2 or 3 tanks it should be much better. Thanks for all the advice. I will keep you posted.

 

[Rolex]

If you're idling well, lean the LSN a little to get it to drive around slowly for another tank, then lean it a hair more. As you start to increase the take off, start leaning the HSN for higher speeds.

 

[joneser4u]

id throw the carb in the garbage and find a old os. carb like a 10e and put on it.