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Discussion Starter #1
I own a 85 Kawasaki GPz 550. I reved up the engine too much and now it sounds louder, and the engine heats up too quickly. So within 5 miles of driving the bike will gradually slow dow doesn't matter how much I accelerate and finally it will shut off.
Does anybody know whats wrong?
 

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An engine heating up too quickly, is in my experience, a bad bearing. It could be a lot of other things as well though. How are you determining its heating too quickly? Is it knocking at all? Does it run poorly before it shuts off, or does it just seem to lose 'oomph' and then shut off? Does it restart shortly after shutting off, or does it not want to start at all?
 

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Discussion Starter #6
it starts up ok but it does not sound like it used to. Then it loses oomph and turns off. It won't turn on until the engine cools down.
 

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The oomph you are referring to is called compression. When an engine warms up, oil flows easier. If there is too much room between the cylinder walls and the pistons, compression becomes to low. If the pistons are not going up and down, the bike doesn't go anywhere.

I don't know of any other way to describe it. I'm not trying to talk down to you.
 

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Poor Running or No Power at High Speed:

Firing incorrect:
Spark plug dirty, broken, or maladjusted
Spark plug cap shorted or not in good contact
Spark plug incorrect
IC igniter trouble
Pickup coil trouble
Ignition coil trouble

Fuel/air mixture incorrect:
Starter plunger stuck open
Main jet clogged or wrong size
Jet needle or needle jet worn
Air jet clogged
Fuel level in carburetor float bowl too high or too low
Bleed holes of air bleed pipe or needle jet clogged
Air cleaner clogged, poorly sealed, or missing
Air cleaner duct poorly sealed
Water of foreign matter in fuel
Carburetor holder loose
Fuel tank air vent obstructed
Fuel tap clogged
Fuel line clogged

Compression low:
Spark plug loose
Cylinder head not.sufficiently tightened down
No valve clearance
Cylinder, piston worn
Piston ring bad (worn, weak, broken, or sticking)
Piston ring/land clearance excessive
Cylinder head gasket damaged
Cylinder head warped
Valve spring broken or weak
Valve not seating properly (valve bent, worn, or carbon accumulation on the seating surface.)

Knocking:
Carbon built up in combustion chamber
Fuel poor quality or incorrect
Spark plug incorrect
IC igniter trouble

Miscellaneous:
Throttle valve won’t fully open
Vacuum piston doesn’t slide smoothly
Brake dragging
Clutch slipping
Overheating
Engine oil level too high
Engine oil viscosity too high
Drive train trouble
 

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Does your engine have oil to the "FULL" mark? If you are low on oil the engine will be louder; real low and you overheat and stop - continue to run it without filling the oil up will result in engine failure.
 

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Discussion Starter #11
I am sorry if I have not been clear with my problem. It was a cold day. I tried to start my bike but it won't start. So after a few tries, when it did start, I revved the engine till it reached the red area on the tachometer. Keep in mind I haven't put the bike in gear yet. After I held it there for a 5 seconds I put it in gear and started to drive. It sounded louder than usual. I mean other sound than the usual firing of spark plugs was going on. 10 mins into driving, I rev the engine to go above 70mph. Usually this is not a problem, but this time the speed went up and gradually came down. I gave it more and more accelerator but same thing. 'I have been driving for 8 months, so I am pretty sure it is not my driving that is making the bike decelerate'. It became harder and harder to accelerate the bike. So I pull into an exit and I stop at the signal light and the bike dies. I leave it there for 4 hours, and I started to again. It start but the sound was still there. 'I don't think it is a knocking sound, because it is not as loud as knocking'. But I suspect something went wrong with the pistons, because the engine would heat up in about a minute. Usually it took around 15 mins for me to feel that heat.

If someone understand how or why this is happening. I would really appreciate it. If you could tell me how to fix it, eg: floating valves, you take the tank off and open the engine up. I would appreciate it even more.
 

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Cold Seizures explained

The text below is reproduced from a posting to the BMAA eGroup, where a member helpfully shared this information - which comes from a Rotax expert - with the group.

First.. the term "cold seizure" is a bit of a misnomer.. All seizures are caused by heat/friction. A cold seizure is where the piston expands faster than the bore it is travelling in and contacts the sides of that bore. These are also known as four corner seizures.

The worst case scenario is that the engine can just lose power and stop. In the case of a mild (mini) seizure the engine may just lose power for a second or two, but will respond to throttle inputs and will recover when the throttle is advanced. This may happen a few times before a major seizure occurs.

Cold seizures "usually" occur after a full throttle run when the engine is powered back to a cruise throttle setting. If the engine has experienced some previous mini seizures, the stoppage can occur anytime in flight as there is already some aluminum (off the piston) attached to the cylinder wall and galling (unwanted removal of aluminum from the piston to the cylinder wall) will be occurring at a variable rate.

In a cold seizure scenario the engine may just sputter and lose rpm for a second or two, or it may bring the engine to a complete stop. Once the engine has cooled down a bit it will appear to re-start and run properly. Don't let this fool you. More than one person has tried to fly his plane out of a field where they had to land because the engine quit, only to have
the engine fail again in short order.. unfortunately, the second failure usually happens when the pilot has fewer options for a safe off field landing. Don't let "gethomeitis" bite you. Find out why the engine stopped before you carry on.. After all, the "self fixing engine" has not yet been invented.

The cause of the cold seizure can be variable. One obvious one, would be a lack of warm up prior to going to full throttle. Also, long extended descents at low power settings followed by a high power run (go around) can also contribute/cause the problem. A major cold seizure (complete stoppage of the engine) can occur as a result of multiple mini seizures finally causing a big time stoppage of the engine.


An easy check for a four corner seizure (cold seizure) is to remove the exhaust "Y" pipe (manifold) and take a peek at the sides of the pistons. If the engine has experienced a seizure, the pistons will tell you the story. On a cold seizure, there will be vertical scuffing towards to outside edges of the piston as viewed through the exhaust port. There will be two corresponding vertical scuffs on the intake side, but these cannot be viewed without removing the cylinders.. If the engine has experienced a cold seizure these marks will be visible through the exhaust ports.

If you have any thoughts that your engine might have experienced a mini through a full seizure, its far cheaper to fix the engine problem than fix both an engine and airframe problem because the engine failed again. The "through the exhaust port" test is simple and definitive!
 

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Discussion Starter #13
thank you

thank you very much that explains a lot. Since I don't have a machine shop or anything like that, I should give the engine to a professional to fix it right.
 
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