Tuning complication engine rich and lean at same time
#1

can’t seem to tune engine properly. Engine will start. Idle fine. But when it is reving up and or wide open throttle is held for more than 2 seconds the engine shows signs of being to lean. Engine carb was reset to a very rich setting. So rich that if idleing fuel will drop out exhaust and engine will need to clear the crank dramatalicly before moving. Once the excess fuel is cleared the lean signs show and cause heating issues as well as burnt glow plugs.
#2

Bad bearings.
#3
Tech Master
iTrader: (2)

Air leak. It could be the carb, exhaust gaskets, pressure tubing, or tank.
Check the exhaust gaskets - engine to header and header to pipe. If the the problem continues I coat the O rings on both the high speed and low speed needle with a thin coating of wheel bearing grease to seal them and replace the pressure fuel tubing. If that doesn't correct it then it is probably engine bearings.
Lee
Check the exhaust gaskets - engine to header and header to pipe. If the the problem continues I coat the O rings on both the high speed and low speed needle with a thin coating of wheel bearing grease to seal them and replace the pressure fuel tubing. If that doesn't correct it then it is probably engine bearings.
Lee
#4
Tech Regular
iTrader: (16)

can’t seem to tune engine properly. Engine will start. Idle fine. But when it is reving up and or wide open throttle is held for more than 2 seconds the engine shows signs of being to lean. Engine carb was reset to a very rich setting. So rich that if idleing fuel will drop out exhaust and engine will need to clear the crank dramatalicly before moving. Once the excess fuel is cleared the lean signs show and cause heating issues as well as burnt glow plugs.
#6

Air leak. It could be the carb, exhaust gaskets, pressure tubing, or tank.
Check the exhaust gaskets - engine to header and header to pipe. If the the problem continues I coat the O rings on both the high speed and low speed needle with a thin coating of wheel bearing grease to seal them and replace the pressure fuel tubing. If that doesn't correct it then it is probably engine bearings.
Lee
Check the exhaust gaskets - engine to header and header to pipe. If the the problem continues I coat the O rings on both the high speed and low speed needle with a thin coating of wheel bearing grease to seal them and replace the pressure fuel tubing. If that doesn't correct it then it is probably engine bearings.
Lee
#7

An engine cannot be rich and lean at the same time. It’s just not possible.
What engine is it?
How is the pinch? How much fuel has the engine seen (realistically)?
What fuel is being used? (Nitro/oil/fuel brand)?
Glow plug brand and heat range / plug #?
Has the fuel system been checked for leaks thoroughly?
Any bubbles in the fuel feed between tank and carb when tank is half full to full is not good.
Unstable fuel mixture tuning and blowing glow plugs is a classic sign of bad bearings causing a crankcase pressure leak. Post pics of these “blown” glow plugs. As clear of a picture of the element itself as possible. It’s easy to spot.
What engine is it?
How is the pinch? How much fuel has the engine seen (realistically)?
What fuel is being used? (Nitro/oil/fuel brand)?
Glow plug brand and heat range / plug #?
Has the fuel system been checked for leaks thoroughly?
Any bubbles in the fuel feed between tank and carb when tank is half full to full is not good.
Unstable fuel mixture tuning and blowing glow plugs is a classic sign of bad bearings causing a crankcase pressure leak. Post pics of these “blown” glow plugs. As clear of a picture of the element itself as possible. It’s easy to spot.
#8
Tech Regular
iTrader: (16)

Like others have mentioned, check to see if there are any blockages in the fuel system. Try blowing back into the pipe and tank on the pressure tube. I would also completely remove the high speed needle and check the banjo fitting to make sure it is clear... all it would take is a grain of dirt to cause a significant restriction of fuel.
#10

A partial blockage of the fuel or pressure line does sound plausible. Alternately the compression ratio could be wrong. If the compression is too low, you'll have to lean-out the HSN too much just to get power; if the compression is too high, you'll have to enrich the LSN and possibly also the HSN to the point that the engine bogs-down frequently just to keep it from overheating. If thoroughly cleaning the fuel system doesn't help, try adding another shim to the shim stack, because it sounds to me like the compression ratio might be a touch too high.
#12

A partial blockage of the fuel or pressure line does sound plausible. Alternately the compression ratio could be wrong. If the compression is too low, you'll have to lean-out the HSN too much just to get power; if the compression is too high, you'll have to enrich the LSN and possibly also the HSN to the point that the engine bogs-down frequently just to keep it from overheating. If thoroughly cleaning the fuel system doesn't help, try adding another shim to the shim stack, because it sounds to me like the compression ratio might be a touch too high.
#13

An engine cannot be rich and lean at the same time. It’s just not possible.
What engine is it?
How is the pinch? How much fuel has the engine seen (realistically)?
What fuel is being used? (Nitro/oil/fuel brand)?
Glow plug brand and heat range / plug #?
Has the fuel system been checked for leaks thoroughly?
Any bubbles in the fuel feed between tank and carb when tank is half full to full is not good.
Unstable fuel mixture tuning and blowing glow plugs is a classic sign of bad bearings causing a crankcase pressure leak. Post pics of these “blown” glow plugs. As clear of a picture of the element itself as possible. It’s easy to spot.
What engine is it?
How is the pinch? How much fuel has the engine seen (realistically)?
What fuel is being used? (Nitro/oil/fuel brand)?
Glow plug brand and heat range / plug #?
Has the fuel system been checked for leaks thoroughly?
Any bubbles in the fuel feed between tank and carb when tank is half full to full is not good.
Unstable fuel mixture tuning and blowing glow plugs is a classic sign of bad bearings causing a crankcase pressure leak. Post pics of these “blown” glow plugs. As clear of a picture of the element itself as possible. It’s easy to spot.