Revo 3.3 Play in starter shaft / Potential air leak
 

Hey guys this is my second revo 3.3 that i purchased new (My original revo is still running like a champ). I'm on about the 10th tank of fuel and have been struggling to tune it and have very high temps. Motor isn't smoking or anything but will reach 300f at the glow plug and forced to shut it down.This engine has ran hot since i got it. I broke in the engine via the traxxas method on both my revos. It doesn't matter how much i richen the HSN it will still act lean and run hot. The engine runs great in 1st gear but once it hits second gear under load it has loss of power and struggles to build rpm. Its also ruining glow plugs frequently, sometimes within a single tank. I can't remember if the issue started when i went to a pull start. I made sure that the backplate wasn't sucking air and there are no visible signs of an air leak. This truck is still very much new with zero exposure to dust, water etc.

I pulled apart the engine and everything still looks new, however there is some side to side play on the starter shaft. Is this normal? Any advice on what to do next would be appreciated!

What fuel (brand, nitro content, oil content), glow plug number/heat range? What does the end of the glow plug look like?

In my 20+ years of running Traxxas, Losi, Novarossi, Picco, OS, and other engines and trucks, I can tell you several things that made a significant difference in how my engines run, tune, and lasted.

1. Never use Traxxas fuel. It has 16% oil in it which is WAY too much. Okay to break in on 16% for the first QUART only. After that, use 11-12% oil fuel. Also, 20% nitro max. More than that is a waste.
2. Preheat the engine to 200°F at the glow plug. You should have mechanical pinch when cold for several gallons if you do all of this right. Pinch is a GOOD thing.
3. Quit using the Traxxas method to break engines in. They are run too rich and too cold and at too low of RPM for the conrod bushings to properly seat. They need RPM and lots of oil to seat. (Ever hear of 3.3’s splitting conrods? Yeah, Traxxas fuel and Traxxas break-in). Take a quart of regular 11-12% oil fuel, and add 2 ounces of castor oil to it. Use this up only slightly rich on the needle and let it rev. Start the engine, run it for 30 seconds to warm it up (don’t baby it, but don’t beat the tar out of it either), and tune the needle leaner so it’s running clean. You want to see it around 220-240°F. Run the quart out using a range of throttle. Full throttle for a second or two, mid throttle, etc. Do not “heat cycle” the engine. It does nothing for ringless ABC engines.
4. Use a long reach medium heat range glow plug. Don’t use HOT plugs.
5. Make sure the throttle linkage moves freely and closes to idle instantly. Check the idle gap - on a new engine, it may need to be opened up to 0.7-0.8mm, however regular running should have an idle gap around .5-.6mm. Wide idle gaps make tuning nearly impossible.

6. The slight play on the starter shaft is normal.
7. LEAN engines quit, burn glow plugs, act sluggish, etc. DO NOT judge fuel mixture strength based on smoke color or amount. Some fuels smoke more than others. Usually high synthetic oil content fuels smoke a lot more because the oil burns rather than stay liquid and lubricate. Castor is more desirable here. Read your glow plugs. Color of body and element, shape of element, surface texture of element are all things you should pay attention to. Reading the glow plug will tell you nearly everything you need to know about how your engine is running and how it’s tuned. A properly tuned engine will have a honey brown color body with a shiny round uniform element. If the body is black and the element is hazy/fuzzy looking, you’re too lean and HOT. 300°F isn’t too hot, but it’s a lot hotter than I like to see. My 3.3s run around 250-260°F on my own 20/12 fuel and a McCoy MC8 or Odonnell SS medium (purple) plug.

This is what it should sound like when it’s rich, but not blubbering rich. This is 10% nitro 14% castor oil fuel I believe.