FrankM
08-21-2007, 03:25 PM
Has anyone experienced the following problem:
I got a new O.S. 18TM for my Revo, broke it in and raced it at the Off-Road Madness event at R/C Madness in Enfield, CT. Engine ran well (although it was hard to restart) and I TQ'd the small-block class with it. After getting home and cleaning the truck in preparation for a photoshoot, it ran well enough for me to re-tune it for the different weather conditions, but then would not run again. It starts and idles, but loses fuel pressure when throttled up. You can see the fuel line dump back out into the tank when it dies. [Note: I have tried different tanks with it to no avail, including a new Kyosho 777 tank]. Now, I suspected an air leak. So, I completely tore down the carb and rebuilt it; everything was fine and the O-rings looked intact. No better. I had a Roto-Start backplate on it, and the one-way doesn't engage the shaft all that well with this setup (the shaft is well recessed on this engine). I removed the backplate and lo and behold, the bearing was toast and the shaft was severely worn, as was the bronze bushing. Okay, I thought, there's my air leak -- not enough crankcase seal to draw in the fuel. I got a new crank and sealed backplate from O.S., installed them, and the same problem occurs. I'm convinced the leak has to be coming from the carb, but this is so uncharacteristic of an O.S. engine; I've never experienced anything like this before -- and all three of my race engines are O.S. I am thinking that somehow air is getting past the slide and its boot. I may just get another carb to try. Any similar experiences/suggestions?
I got a new O.S. 18TM for my Revo, broke it in and raced it at the Off-Road Madness event at R/C Madness in Enfield, CT. Engine ran well (although it was hard to restart) and I TQ'd the small-block class with it. After getting home and cleaning the truck in preparation for a photoshoot, it ran well enough for me to re-tune it for the different weather conditions, but then would not run again. It starts and idles, but loses fuel pressure when throttled up. You can see the fuel line dump back out into the tank when it dies. [Note: I have tried different tanks with it to no avail, including a new Kyosho 777 tank]. Now, I suspected an air leak. So, I completely tore down the carb and rebuilt it; everything was fine and the O-rings looked intact. No better. I had a Roto-Start backplate on it, and the one-way doesn't engage the shaft all that well with this setup (the shaft is well recessed on this engine). I removed the backplate and lo and behold, the bearing was toast and the shaft was severely worn, as was the bronze bushing. Okay, I thought, there's my air leak -- not enough crankcase seal to draw in the fuel. I got a new crank and sealed backplate from O.S., installed them, and the same problem occurs. I'm convinced the leak has to be coming from the carb, but this is so uncharacteristic of an O.S. engine; I've never experienced anything like this before -- and all three of my race engines are O.S. I am thinking that somehow air is getting past the slide and its boot. I may just get another carb to try. Any similar experiences/suggestions?