Question about 2002 Hyosung RX 125

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Hyosung RX125 I have a slight knocking from the engine. I adjusted the valve clearances to their proper settings but still no change. I dismantled the the engine further but could see no obvious problem. However when putting the timing chain back on, I can only turn the crank approx two cycles before to comes to a dead stop. What could this be??? Note: I have set the timing as per the manual, however I did accidentally drop the chain and turn the crank whilst the cam was not connected. After some time retrieving the chain, I reset the timing so that the marker on the crank corresponded to the cam being TDC. Does anyone know why I can only turn the crank approx two cycles before to comes to a dead stop?

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  • John May 18, 2009

    Hyosung RX125

    I am having trouble setting the timing on my RX. I have rotated the cam several times as this could be 180 degrees out, however still can't seem to get it correct.

    Is there a specific method of setting the timing?

  • John May 19, 2009

    I have a service manual, however it doesn't give a solution to this scenario. You are correct in that the cam gear has two horizontal markings and must be lined up with the surface of the valve cover when the piston is at TDC. The cam however also has two references ('B' and '-') associated with the horizontal markings. Do these have to be a certain way up (i.e 'B' on the bottom and '-' on the top for example)?

    I will remove the cylinder head and check the valves as suggested.

    Much appriciated

  • John May 21, 2009

    The marks are 90 degrees to the horizontal. I have positioned the cam as mentioned, however I have noticed that when I turn the crank one full cycle, the timing becomes out slightly. On the second full turn of the crank, the timing becomes even more out. After about the third/forth turn, the crank comes to a hault. I would be tempted to suggest this to be the timing chain, althought the engine was running fine before I dismantled the timing chain.

    I lifted the head and all valves seemed to be seated ok. I didn't take the head off fully as this requires the engine to be removed from the frame. Would a bent valve cause this sudden halt on the crank? Also, I'm assuming a bent valve would not seat properly. Do you agree?

  • John May 25, 2009

    I have checked the valves and they seem fine. I even disconnected the timing chain and positioned the crank such that the piston was located at the bottom of the engine. I then turned the cam shaft several times; all valves opened and closed a per normal.

    The problem seems to be when I connect the chain. Even when I reset the chain such that the chain is tight from the cam gear to the crank gear on the front side of the engine, the marker points do not line up after two or three revolutions. This happens every time and seems to be knocking the timing out. I would assume the chain to be stretched, however the timing seemed fine before I dismantled the engine, also I would expect the chain tensioner to overcome this.

    I have been asked previously if the chain is seated correctly on the crank end cog. I cannot see clearly inside the engine, however surely the chain would slip resulting in a greater timing mismatch than what I have? Any suggestions?

  • John May 28, 2009

    I've finally got it sorted. The timing chain was seated between the cog and the engine, causing the timing to slip. I've turned it over and seems to run fine.

    Thankyou for your help, it is much appreciated.

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It sounds like you have the cam 180 degrees out of time. The engine locks up because the piston is hitting an open valve. Hopefully the valve is not bent.

Posted on May 17, 2009

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  • tombones May 18, 2009

    Rotate the cam such that the high points of the cam are not lifting any valves when the piston is at Top Dead Center, ( TDC), as indicated by the timing mark on the flywheel. The cam should have one or two reference marks stamped into the gear. If only one mark, then it is usually lined up with the center-line of the piston. If two marks, then the marks are usually lined up with the surface of the valve cover.



    It would be best to remove the cylinder head and be certain the valves are not bent. Look for a strike mark on the top of the piston from where it hit a valve. Look at the valves. Are they fully seated? If a bent valve is found then check the valve guide very closely. Is the guide bent, broken or cracked? If so, you will need to replace the bad valve guide when installing a new valve. After installing the cam chain, slowly turn the crank several revolutions by hand to be sure the piston is not going to strike a valve.



    I don't have a service manual for your bike so I am operating somewhat in the blind here. I advise that you either get a factory service manual or at least check with the dealer to confirm the information I have given.

  • tombones May 19, 2009

    Are the marks " B and - " at 90 degree angles to the horizontal markings? Chances are the "B" is bottom but again, rotate the cam such that the high points of the cam are not lifting any valves when the piston is at TDC. Where is the "B" at in that configuration?

  • tombones May 21, 2009

    With the cam marks in position, reset the chain such that the chain is tight from the cam gear to the crank gear on the front side of the engine. All slack in the chain is now at the back of the engine. Now engage the cam chain tensioner. Now it is impossible for the timing mark to advance with each revolution of the crank. If the engine still locks up there is a 99% likelihood that a valve is bent and the engine locks up when the piston pushes against the bent valve.



    If the piston hits a valve, the crank can suddenly stop turning. If a valve is bent it is impossible for it to seat properly. Pull the engine from the frame > it is not that hard to do. Now take the engine in and have the dealer check the valves. Chances are that you will need a new valve or two and possibly new valve guides. The best part is that the dealer will put the engine back together and ready to run. Now you can put it in the frame and then go for a ride.



    By the way, the original problem, a slight "knock" in the engine, is probably detonation, aka: pre-ignition, aka: engine knock. Have the dealer de-carbon the head and piston crown. Use only premium gas. Install a new stock spark plug specified for your bike. Do an oil change, (10w40 motor oil), including oil filter if your bike has one. Check the carb intake for leaks. New carb and intake manifold gaskets are recommended. An air leak will lean the fuel mix and cause the engine to run hot, thus promoting detonation.



    After your first ride, feel free to change the rating to "solved the problem". Best wishes, tombones49 :)

  • tombones May 25, 2009

    It is impossible for the timing to advance with each revolution of the crank unless the crank sprocket or the cam sprocket is slipping on its' shaft. That is not likely. Reset the cam as previously mentioned. Rotate the crank FOUR times. Check the marks now. If the engine locks up I think it is time to take it to a dealer and have them check the valves and set the timing.

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Hyosung rx 125 model 2004 too 2005 please send me your best quotation thank you and best regards mohsen.jvd

Posted on Feb 05, 2011

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Kia sorento 2012 produce sound look like power steering problem and it gets louder when ever I acceleration gear, so I took belt out and start the engin with no belt I found that sound was in engin!!


If its a knocking sound:

A KNOCKING SOUND IN THE ENGINE IS MOST LIKELY CAUSED BY ONE OF THE FOLLOWING
1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.

3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
4. REAR MAIN BEARING KNOCK: Makes dull knocking or thud noise. Detected at speeds between 20 and 50 MPH. Knock will normally decrease or disappear while pulling or decelerating. Noise will be detected the loudest at normal driving speed, when not pulling or decelerating. Correct by adjusting bearing clearance to .001 to .0015 inches. If knock is excessive, crank should be checked for out of roundness. May need to re-pour all main bearings to correct.
5. TIMING GEAR KNOCK: usually the most difficult to diagnose. If gear is loose or badly worn it will knock in all ranges. Run engine slightly above idle speed. Slowly open and close throttle. Knock will continue to be present, but just as engine slows down knock will become a slight rattle. Remove timing pin and reinsert into timing hole on timing gear cover. Press timing pin tightly against timing gear and accelerate slightly above idle. Knock will significantly be reduced or disappear. Correct by replacing both timing gear and crank gear as a matched set. The two gears should have a backlash clearance of .003 to .004. If more than .009 inch backlash, an oversize (.005) timing gear should be installed.
6. WRIST PIN SLAP: This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. This can be corrected by installing a new wrist pin bushing in the rod or new wrist pin f badly worn. Wrist pin should fit the piston and connecting rod with a tight metal to metal fit. The pin can be pushed into the piston and rod with a slight pressure of the hand. Pin to rod clearance is .0003 to .0005 inches.

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TROUBLESHOOTING ENGINE NOISES
A KNOCKING SOUND IN THE ENGINE IS MOST LIKELY CAUSED BY ONE OF THE FOLLOWING
1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.

3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
4. REAR MAIN BEARING KNOCK: Makes dull knocking or thud noise. Detected at speeds between 20 and 50 MPH. Knock will normally decrease or disappear while pulling or decelerating. Noise will be detected the loudest at normal driving speed, when not pulling or decelerating. Correct by adjusting bearing clearance to .001 to .0015 inches. If knock is excessive, crank should be checked for out of roundness. May need to re-pour all main bearings to correct.
5. TIMING GEAR KNOCK: usually the most difficult to diagnose. If gear is loose or badly worn it will knock in all ranges. Run engine slightly above idle speed. Slowly open and close throttle. Knock will continue to be present, but just as engine slows down knock will become a slight rattle. Remove timing pin and reinsert into timing hole on timing gear cover. Press timing pin tightly against timing gear and accelerate slightly above idle. Knock will significantly be reduced or disappear. Correct by replacing both timing gear and crank gear as a matched set. The two gears should have a backlash clearance of .003 to .004. If more than .009 inch backlash, an oversize (.005) timing gear should be installed.
6. WRIST PIN SLAP: This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. This can be corrected by installing a new wrist pin bushing in the rod or new wrist pin f badly worn. Wrist pin should fit the piston and connecting rod with a tight metal to metal fit. The pin can be pushed into the piston and rod with a slight pressure of the hand. Pin to rod clearance is .0003 to .0005 inches.

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A KNOCKING SOUND IN THE ENGINE IS MOST LIKELY CAUSED BY ONE OF THE FOLLOWING
1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.

3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
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6. WRIST PIN SLAP: This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. This can be corrected by installing a new wrist pin bushing in the rod or new wrist pin f badly worn. Wrist pin should fit the piston and connecting rod with a tight metal to metal fit. The pin can be pushed into the piston and rod with a slight pressure of the hand. Pin to rod clearance is .0003 to .0005 inches.

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1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.

3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
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Depends on which engine you have. If you have


ADJUSTMENT Although it is sometimes possible to reuse an old cylinder head cover gasket, in most cases it makes more sense to purchase a new one before beginning the procedure. Some vehicles may require the use of silicone sealant either with or without a new cover gasket. For more details, please refer to the cylinder head cover procedures in Engine & Engine Overhaul of this repair guide and refer to the gasket manufacturer's instructions.

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See Figures 1, 2 and 3
For the intake valves: 1-4-5-8 valve clearance is 0.012 in. (0.30mm). For the exhaust valves: 2-3-6-7 valve clearance is 0.012 in. (0.30mm). The pivot locknut torque specification is 12-16 ft. lbs. (16-22 Nm).

  1. The valves must be adjusted with the engine warm, so start the truck and run the engine until the needle on the temperature gauge reaches the middle setting. After the engine is warm, shut it off.
  2. Note the location of any wires and hoses which may interfere with cylinder head cover removal, disconnect them and move them to one side. Remove the bolts holding the cylinder head cover in place and remove the cover. Remember, the engine will be hot, so be careful!

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Fig. Fig. 1: Check the valve clearance with a flat feeler gauge-Z24i engine





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Fig. Fig. 2: Loosen the locknut and turn the adjusting screw to adjust the valve clearance-Z24i engine


1c1d35c.gif


Fig. Fig. 3: With the No. 1 piston at TDC, adjust the top set of valves FIRST; with the No. 4 piston at TDC, adjust the bottom set of valves SECOND-Z24i engine

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  2. Refer to the accompanying illustration (upper part), then check valves (1), (2), (4) and (6) using a flat bladed feeler gauge. The feeler gauge should pass between the valve stem end and the rocker arm screw with a very slight drag. Insert the feeler gauge straight, not at an angle.
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  5. See the illustration (lower part), then check valves (3), (5), (7) and (8). Check and adjust valve clearance as necessary.
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See Figures 4 and 5
These models utilize hydraulic valve lifters. Periodic adjustment is neither necessary or possible. There is however a bleed down procedure that is necessary when the valve train has been disassembled.
HYDRAULIC LIFTER BLEED DOWN
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Fig. Fig. 4: Cross-sectional view of an installed hydraulic valve lifter-4 cylinder engine


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Fig. Fig. 5: Cross-sectional view of an installed hydraulic valve lifter-6 cylinder engine

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Hyosung RX125 I have had an oil leak ever since I dismantled the engine last month. There was a slight knocking, however I went out on it last weekend regardless. The bike started to lose power after 2...


Is your bike making blue/blueish smoke while running? From the stuff you told us, it is either worn piston rings or worn valve seats, but i would personaly bet it's the valves, because the knocking sounds would be the valves being severely out of adjustment, leading to a huge loss of power and many noises. Hope i helped you :)

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