mleech

I am NEW to Nitro RC I just got my Revo 3.3, I went through all of the break in procedures to a T that were outlined by Traxxas and on my 6th tank I broke the connecting rod. Is this a typical issue or could I have done something wrong?

jwm2

iTrader: (5)

Those engines are pretty tough. Chances are you didn't warm it up enough prior to starting the engine. In the beginning the pinch on the sleeves is very tight and can stress the Conrod. You'll need to get a new conrod of course and then continue the break in procedure. Maybe give it a 1/8 turn to the left to thin out the hsn prior to starting it up, that should help alleviate some of the pressure from the fuel to air mixture that was putting extra stress on the conrod during break in.

spookie

iTrader: (25)

I made my son go through 10 tanks before leaning out on his new 3.3. Is it cold there? That will affect breakin length. Personally I would slap another rod in it and finish breakin properly. I checked, yeah it's cold there. Cold weather you should richen the engine.
Location: Richmond International Airport
Temperature: 44 °F
Comfort Level: 42 °F
Dew point: 38 °F
Pressure: 29.87 "Hg
Humidity: 79%
Visibility: 10 mi
Wind: 5 mph from 0° NorthDirection South
Last update: Tue 11:54 AM EDT

mleech

lol yeah its a little cold here but I wrapped the head in foil like traxxas suggested and the temp after warm up was around 250

mleech

I sent the engine into traxxas to hopefully to be warrantied but when I get the new one should I let it idle until its up to temp before I proceed with break in all over again?

jwm2

iTrader: (5)

If you have a heat gun i'd heat it up to about 150-180 before cranking it over. If you don't have a heat gun then you can use a hair dryer to get it as warm as you can before starting it. Most of the stress is coming from starting it cold. Right now the pinch is at its greatest, so starting it cold will add more stress to the conrod, especially in 40-50 degree temps. Couple that with the fact that you almost have to run it rich to get it to run properly and its no wonder the conrod snapped. When you run the hsn rich you are actually putting more pressure on the conrod which can shorten its life, but in the conditions you are currently in you probably don't have much of a choice. If you are in high elevation then chances are the trifecta is what did it in and will most likely happen again once you do get it back. Either wait for the weather to warm up, move to lower ground or heat up the engine prior to cranking it over. If you try to start it in high elevation with cold weather and without heating the engine block up prior to cranking it over, theres no doubt in my mind you'll have another broken conrod before you finish breaking it in.

Ok i just checked google and elevation isn't a problem it puts you at just over 300ft above sea level. I know there are mountains in virgina so i wasn't sure. I am at about 600ft above sea level in grand rapids mi.

spookie

iTrader: (25)

Yes! Good point. Sometimes the pinch is so tight being cold, it stresses the rod on the downstroke. I actually have a 500 watt heater I use to bring them to temp before trying to start. It can be 35 degrees, and 4 or 5 minutes in front of the heater they start right up. Of course without wrapping the head, they'll cool down while I'm running them. But not stone cold. That's why I have a winter and summer body. The winter one is tight, holds the heat in, and the summer has lots of windflow.

mleech

Thanks for the pointers guys!
I will go buy a heat gun if that will keep this from happening again! When Its cold outside even after break in should I heat it up before starting it?

Two bodies one for winter and one for summer that's a great idea I will have to try that!

spookie

iTrader: (25)

Just go down the the local dollar store and get you one of those $15 small cube heaters. Set it close enough that the warm air blows over the engine, but not close enough to burn up anything. I never leave mine unattended while I do this this. The engine will feel very warm when it's ready, maybe 5 minutes if that, almost like you just ran it. Then fire it and start the breakin always watching the smoke from the exhaust. You're on the right track monitoring temps with a thermometer. While you have the engine out, I would drill the easystart and do the mod for a shot of WD40 into it. I did this, only I drilled a small hole just for the WD40 tube size. Believe me, you won't regret this. When the OWB, one way bearing, starts to slip, and it will, just give it a shot through the hole with the WD. Instant fix. I would take it easy until I had used maybe 1/4 to 1/2 a gallon through it.
Eta. if you have to stop the breakin and won't be running the car right away, take the glow plug out and push the piston all the way down. This keeps it out of the pinch area at the top of the cylinder as it cools and contracts, and prolongs engine life and compression.

+ YouTube Video