WOW, pretty harsh guys, tough crowd I guess. Alright, I'll give you a quick rundown on how to inspect the motor to see if things are up to par or not.
1.) Checking pinch- clean around the glow plug with some solvent and compressed air. I use carb spray. Remove glow plug and slowly rotate motor and watch the piston as it approaches top dead center. The piston should start to pinch on the sleeve a little. If it doesn't it doesn't mean its not any good, it just means its either well broken in or approaching replacement time. You could also get it pinched from a reputable company for under $25.
2.) Checking for air leaks- If the motor has been run and there is dirt on it, check for saturation around the carb area(where it seats to engine and around needles), lower front bearing near the clutch and around the head gasket. If there isn't any signs of fuel saturation in those areas then you are in good shape with that. If you what looks like wet dripping sludge in any of those areas, make necessary repairs.
3.) Checking fuel lines- inspect all fuel lines (pressure and fuel) from the pipe to the tank and from tank to the carb. Also check the filters if you have any.
4.) Tank Inspection- A simple way to do this is to blow lightly into the return line to see if you have any fuel being forced up to the carb. Don't blow hard, just a nice steady pressure is all it should take.
5.) Inspect Pipe- Check to make sure pipe is seated to the exhaust flange properly and that there are no cracks or other restrictions that could cause low or no backpressure situations.
6.) Setting Needles- There are several ways to do this but I'll give you the easiest way to do it. Set the High and Low needles to 3 turns out from seated. Start motor only if steps 1-5 are good to go. The motor should fire up, it may run eratic but thats ok for now. Start turning the high speed needle out and rev the motor a few times wide open. Only rev it at WOT for about a second or two. Don't pin it and hold it there. All you are trying to do is see if the high speed is in the ballpark. If you rev the engine and it sounds blubbery, lean it in a 1/4 turn at a time until the needle no longer responds or the rpm doesn't change much. Once you are there back it off a 1/4 turn and leave it for now. Next let the vehicle come an idle and pinch the fuel line and count the seconds it takes for the engine to stall. If set up correctly, the idle shouldn't change at all for the first few seconds indicating great fuel signal and needle pressure, then the idle should raise for about 2-3 seconds and then the motor should die out. If the motor speeds up as soon as you pinch the line, its too lean and if the motor idles for more than 6-8 seconds before idleling up or stalling then it's too rich. Play with it until you get it where you want. After that, set the car down and run it for a little while checking the temp to see if it is heat saturatin. If the temp continues to rise past 260-270, back off the high speed screw until temps maintain. Your motor should be somewhere between 220-250 when tuned correctly. Some engines run a little hotter so 270 is not uncommon. It should definately stay under 290. I have never had an engine run over 285 that was tuned correctly. After you think the engine is running decent, come to a stop and let it idle for 8-10 seconds and then stab it. If you see smoke and it sounds like it blubbery, then its rich. Lean the low end in a 1/8 turn at a time and repeat test until you achieve the desired response. If tuned correctly, the engine should be able to idle for 10-15 seconds and snap to life when you pull the trigger and should only have a very mild richness to it when idling over 30 seconds.
If you have tried all of the above and nothing works, then the motor might be tired and may need a rebuild or replacement. Due to the lack of rings in these engines, the piston to wall clearance is critical for creating the vacuume necessary for each cycle. if you have any questions, feel free to give me a call.
Mark @
www.PowerHouseRCPerformance.com