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Tuning complication engine rich and lean at same time

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Tuning complication engine rich and lean at same time

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Old 02-04-2019, 02:56 PM
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Default Tuning complication engine rich and lean at same time

canít 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.
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Old 02-04-2019, 03:15 PM
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Bad bearings.
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Old 02-04-2019, 03:25 PM
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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.

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Old 02-04-2019, 06:03 PM
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Originally Posted by illmatic94 View Post
canít 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.
Sounds like you pretty much answered your own question... fat on bottom and too lean on top.
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Old 02-04-2019, 06:10 PM
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Originally Posted by Juice1 View Post
Sounds like you pretty much answered your own question... fat on bottom and too lean on top.
you would think it was that simple . Nothing fixed it. Was constantly fat until the crank cleared then immediately overheated or cut out from NO fuel .
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Old 02-04-2019, 06:11 PM
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Originally Posted by Winner's Circle View Post
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
pressure tube? Like from the exhaust to the engine? Also would seeing bubbles in the fuel line to the engine be of any significance?
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Old 02-04-2019, 06:16 PM
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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.
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Old 02-04-2019, 06:41 PM
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Originally Posted by illmatic94 View Post

you would think it was that simple . Nothing fixed it. Was constantly fat until the crank cleared then immediately overheated or cut out from NO fuel .
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.
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Old 02-04-2019, 08:03 PM
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I've seen this happen when the tank / fuel line isn't getting pressurized. You can richen the HSN all day... you pull the throttle, engine will clear, lean out, starve itself for fuel, and flame out.
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Old 02-04-2019, 08:35 PM
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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.
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Old 02-04-2019, 08:37 PM
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Originally Posted by E1 Diablo View Post
I've seen this happen when the tank / fuel line isn't getting pressurized. You can richen the HSN all day... you pull the throttle, engine will clear, lean out, starve itself for fuel, and flame out.
thatís my exact problem. I help alleviate some of the issue by changing the pressure line as well as a rotted seal between the manifold and muffler but the issue is still there just not as bad.
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Old 02-04-2019, 08:38 PM
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Originally Posted by fyrstormer View Post
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.
engine has good compression when cold. Doesnít seem worn at all. I am running 30% fuel
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Old 02-05-2019, 06:02 AM
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Originally Posted by SlowLST2 View Post
An engine cannot be rich and lean at the same time. Itís 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 ďblownĒ glow plugs. As clear of a picture of the element itself as possible. Itís easy to spot.
Again what engine is this? Change all fuel lines, exhaust seals, glow plug, air filter. Make sure carb is not loose either. Set needles to factory and start over.
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Old 02-05-2019, 07:54 AM
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Originally Posted by sebtarta View Post
Again what engine is this? Change all fuel lines, exhaust seals, glow plug, air filter. Make sure carb is not loose either. Set needles to factory and start over.
I donít believe the engine brand would change any of the symptoms. Itís a Losi 454. Iíve changed everything . Thereís no leaking bearings either.
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Old 02-05-2019, 10:50 AM
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Originally Posted by illmatic94 View Post

I donít believe the engine brand would change any of the symptoms. Itís a Losi 454. Iíve changed everything . Thereís no leaking bearings either.
Get a can of carb cleaner. With the engine running spray the front bearing behind your flywheel. If it changes the way your engine is running you have a leaky front bearing.
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