Nelson Q500 Break In Technique - Randy Bridge

I met briefly, and I mean briefly, Randy Bridge at the 2002 AMA Nationals in Muncie, IN. He and fellow racers had come over to the combat field to check things out. Early in 2004, during my quest to get back into racing I decided to be bold and send Randy an e-mail. I figured he probably wouldn't remember me but what the heck, what did I have to loose. I asked questions about his techniques, specifically about breaking in a new Nelson Q500 motor. Not knowing him, I wasn't sure if he'd take the time to share his speed secrets.

I was blown away, and continue to be blown away, by Randy's openness and willingness to share his experiences. He has answered every question I've ever asked and believe me, there have been many. I used this technique to break in my first new Nelson. The motor is as strong as any I've flown against. I figure if it works for the reigning 5 time AMA Overall Pylon National Champion (that's five in a row), then it's plenty good enough for me.

Thanks RB.

Randy Bridge:

Everyone has there own theories on how to break in a Q500 motor. Here is mine.

1. Start with the motor set up. Set the liner/deck height at the .190”. You can't go wrong there, and you'll never need to change that again. The head spacing should be around .010" total clearance, but for your first 5-10 runs you should leave the head up a bit higher (.012" or .013”). This will reduce your chances of getting the motor too hot during break in. After those 5-10 runs, you may want to get down to .010”, BUT... No lower.

2. Prop? You want something that will hit 20k rpm. Some guys put a FAI pylon prop on and run them in on the ground at around 26k. So don't worry about the rod or wrist pin, it will hold up to around 30k.

3. Run it first before flying it. No need to run it long. Start it up and let it run pretty rich for about 30 seconds. That should clean all the debris out of it and should help set the bearings. Then turn in the needle so that it is on the pipe (about 18k to 18.5k). Shut it off and let it cool. Refuel. Go fly it. This time start it up rich again. Screw the needle in until it gets to 18.5k and pinch your fuel line and see what it does (rpm). You'll probably have to launch at about 18.5 to 19k, but no higher. Do that for about 3 flights. You can now start running it a bit leaner, still using the 20K prop. An 8.75 x 8.5 or 8.8 x 8.5 should get to 20k without much problem.

4. Once you have 5-7 flights on it. Use some more prop, 8.75 x 9.0W or 8.8 x 8.75. Still run it rich. Meaning, make sure there is always about 600-800 rpm of pinch up in the motor. These props will not turn the same. The 8.75 x 9.0W should hit 20k. The 8.8 x 8.75 may hit 20k but may not. Remember the head spacing is about .002” to .003” high still. You can lower the head to .010" if you wish. You'll certainly see more static rpm on the ground. Just remember your 600-800 rpm pinch up rule.

5. When you hit your 10th run. You're pretty well broke in.

You just want to avoid really stepping on it until around 20 runs.

Is it a "stump puller" motor? Who knows, but here is what I turn some props:

8.8 x 8.75 = 19.8K to 20.0K rpm
8.8 x 9.25 = 19.2K to 19.5K rpm

You shouldn't need to change much with the weather changing. If it gets hot and humid, you could raise the head .002". I rarely change, I just needle it differently. Mostly set it richer when it's hot.


 
Published: 11.14.2004