Quickie JETT QM40
Operating Instructions
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Thank you for ordering the Quickie-Jett Quarter Midget .40 Engine from Jett Engineering. We believe that it is the finest, most powerful engine in its class. If you have any questions or comments, please give us a call any time during working hours, 8-5 central time, at 713-680-8113, or visit our web site at jettengineering.com.
PROP: A high performance engine should have a well-balanced prop to perform well. Reinforced Nylon, Carbon Fiber or Fiberglass are OK, but use extra care to avoid injury. Pick a prop which turns at least 24000 RPM on the ground to get the best needle valve behavior.
PLUG: We get the best RPM from the Nelson HD type plug.
BREAK-IN: There are many theories on break-in. ABC and AAC pistons and liners need very little. However, your rod and other moving parts need to be well seated before they can perform reliably. Piped engines and specifically piped AAC/ABC engines tend to work against you during break-in. To adequately loosen up an AAC/ABC (which has some interference fit) it must be hot. This means running it fast and hard, but you must do that before you break in the rod--Catch-22. This is why almost anything works as well as the next. This is what we do: We run your engine for you and take the first chance. After we start it we heat it up immediately, but not all the way to the peak. We run it rich at about 17500 for about 30 sec., then we run it for several minutes at about 22000. We allow the engine to cool and finally test, very carefully for peak RPMs. THIS ENGINE IS NOT BROKEN IN.
When you get the engine, open the needle FIVE turns and crank it up on a very small test prop that is capable of turning at least 27000. Usually an APC Q-500 prop cut off to about 4 or 5 inches will do the trick. Lean the engine in until it is staged on the pipe and running about 22000. If it isn't still rich, change to a smaller prop. Let it run there for 15 min. Lean the engine in to about 26000 (still rich) and run it about 5 min. You should be able to fly, but be careful!!
TANK: A six oz. Bubbleless JETT tank works well for QM-40. We do not recommend any other tank except the Tettra bubbless CLEAN YOUR TANK AND EQUIPMENT OFTEN AND USE A FILTER IN YOUR PUMP. Do not mount your engine upright. You will experience fuel flow problems because the tank is too low. Turn your engine sideways so the engine won't have to draw up hill. If you have engine problems, look at the tank first!!!! This is where we find most problems. ABOUT 80% OF THE TROUBLE CALLS WE GET ARE ULTIMATELY FOUND TO BE TANK PROBLEMS.
The engine should run almost a full tank of fuel on the ground without changing RPM significantly. Look for air bubbles in the fuel line while running with 1/3 full tank. You should have no air in the fuel line. A tank that is not bubbless must be perfectly isolated by thick, dense foam, around all sides, and front and back. Take the time to do this, along with making sure you have new, good tubing in and outside the tank, and above all else, no leaks.
ADJUSTING THE NEEDLE VALVE FOR FLYING: Your engine should be set slightly rich as you received it, but open it one more turn just to make sure. Start the engine and make sure you have a good working Tach. HINT: Put your finger over the pipe for one second to prime the engine. The engine should be too rich to take off the battery, so start to lean it in (clockwise). The engine should start to move up the stages of the pipe and be running above 20000 quickly. Continue to lean it in until the engine starts to smooth out, but still has the "crackle" of a rich setting. If the prop is right it will now be turning at least 22000. The final peak may come quickly and be a jump above 24000. Back down from there and experiment to get the best setting.
After getting the right prop, open the needle valve a turn, start it up and slowly lean in the engine until the peak RPM is found. Expect the engine to smooth out, then slowly sag as it gets lean and overheats, quickly open the needle 1/2 turn and let the engine cool. Now you know where the peak is - always stay on the rich side of the peak.
MAINTENANCE: Your engine is designed to last for many races, but care must be taken to avoid lean runs. A few laps lean will take away hours of life. If you are getting good solid runs and you are never blowing a glow plug, you may be able to lower your head some. Your engine comes with several .002 shims. Carefully remove one and try it again. Use care in removing and tightening the head. We suggest you have someone help you if you are inexperienced. An improperly torqued head will ruin you piston and liner fit in just a few seconds running.
Use a good after-run oil to protect your bearings. We use Marvel Air Tool oil, found at machine tool stores.
Your muffler has stainless steel screws on purpose. They break when you crash and will do less damage to the engine and muffler. Your muffler is assembled with a special high temp adhesive, so if you need to reassemble it for any reason, return it to the factory, or use "red" Loctite from the auto store. (The red will only work for emergency repairs)
Proper installation of internal engine parts is important, so we recommend you let us do that. If not, we will be glad to assist you in any way.
We hope you enjoy your new Jett engine. If you have any questions, call us at (713) 680-8113. HAPPY FLYING!!!
