RE: Ofna LX GT pro
Is this what I should do? This thing where you put the piston at the bottom of the sleeve seems hard to do. Do you recomend this? Or should I just run it around rich and lean each tank?
Step 1. The first few runs of your new engine are critical. Once your engine starts, place the car on a stand so that its wheels can't touch the ground. Let the engine idle at low rpm for a few minutes (two or three minutes will do), then shut the engine down and let it cool. During this procedure, it's also important that the piston not be at the top of the cylinder while the engine is cooling. Part of what's taking place during break-in is that the engine's mating parts are being heat-cycled, which means they are expanding when the engine is hot and contracting when it cools. Heat cycling stabilizes the metal and allows mating parts to fit better against each other. Keeping the piston out of the upper portion of the cylinder (which is smaller in diameter than the lower portion in order to create a better seal during combustion) will allow the cylinder to properly contract as it cools-without interference from the piston. To figure out where the piston is in relation to the cylinder, just turn the flywheel-it will become difficult to turn when the piston is at the top of the cylinder, where the fit between the piston and cylinder is its tightest. Just turn the flywheel until the piston is in the middle of its "easy turning" part. Repeat the above steps three or four more times.
Step 2. After you've heat-cycled your engine, you can finally put it on the track. But don't get too excited yet - you must run it with a very rich high-speed needle setting. Lots of blue smoke should be coming from the exhaust, and the engine should sound "blubbery." During this procedure, it's vital that you avoid prolonged use of full throttle, which could strain the engine. You should instead "blip" the throttle as you drive the car to avoid spending too much time in one particular rpm range. Run the engine using these settings for three or four tankful's of fuel, allowing the engine to cool in between runs.
Step 3. Once you've put about six to eight tanks of fuel through the engine (as outlined above), it's time to begin leaning the high-speed needle and making some power! Begin by leaning the high-speed needle (by turning it inward, or clockwise) by about one-hour (if you imagine the needle as a clock face, one full turn of the needle would equal 12 hours). Run the car for a minute or so, then bring it back in and lean the needle by another one hour increment. Repeat this process until the engine begins to achieve good rpm, but it shouldn't be allowed to "scream" quite yet. The engine should still be creating lots of blue smoke from its exhaust. Before you achieve that screaming race setting, we recommend that you run your engine for a few more tankful's in this "almost race" setting. Once you get the needle set to where your engine is making good rpm, richen it (by turning the needle counter-clockwise) by about a quarter of a turn-this is your final setting.
Step 4. Once you've found a good setting for the high-speed needle that allows the engine to make good power yet still push plenty of blue smoke from the exhaust (especially when the car exits a turn), it's time to set the low-end needle and the idle-stop screw. For now, set the idle-stop screw so that the engine will idle at a moderate rpm without stalling. Bring the engine up to operating temperature by driving it for a few minutes. Now stop the car and listen to the engine's idle speed. If the engine idles fast but then slows down in just a few seconds, the low-speed needle is probably set too rich. Lean the low-speed needle (by turning it clockwise in one-hour increments) until, after running a few more laps, the idle stays high for about twenty seconds or so when you stop the car. Once you've done this, use the idle-stop screw to make the final adjustment of the idle speed. Setting your engine's idle speed isn't a contest to see how low you can get it without stalling the engine! Your goal when setting the idle should be to allow the engine to run at moderate rpm without the clutch being engauged whatsoever. Your car should be able to sit at a standstill when idling. If you have to hold the brake, the idle is too high. If you have to blip the throttle to prevent stalling the engine, the idle it too low. Afterthought: Nitro powered R/C vehicles can be tons of fun, or they can cause tons of frustration. The difference between success or failure lies with the break-in process. If you follow these steps, have patience, and use your noggin, you're assured of success. Rushing through the break-in procedure or worse, forgetting it altogether, is a recipe for disaster. Tuning your engine is the hardest part of nitro racing. But once you've learned how the carburetor works, and which screw does what, it will all become second nature. So when you're running your car, you'll always know exactly what to adjust to gain the highest level of performance possible.