i bought a 99 kx125 the was flooded in a big mud puddle, then parked for over a year. 2. Spoke to live tuner and he is confident that 8500rpm is not to high and suggest it could have being worn shell, weak bolt or oil pump starvation if its not 100%. Another type of engine knock is rod knock. Any idea why a bearing would fail this early? It will show a lot of iron if you analyze oil with Blackstone Labs. Bad rod bearings, piston slap and piston pin noise usually get more quite when you pull off the spark plug wire as noted above. I pulled apart the oil pump and cleaned it up. The Common Engine Bearings Used In Engines Are: Main Bearings. The following are causes of main bearing noise: A bad lifter will make a clacking noise, about 1 clack per second at idle and throw a cylinder misfire. An upper and lower. If the bearings … Most engines have at least two main bearings. Excessive crankshaft end play is indicated by an intermittent rap or knock sharper than a worn main bearing. The balancer bearings felt fine, as did all of the transmission bearings. with the bike off you can hear the noise when pulling the kicker down slow, which is what leads me to believe its the bearings. If your vehicle has a worn out main engine bearing or rod bearing, your car will usually display some or all of the common symptoms: Knocking Noises - If your car engine knocks upon starting the car, there is a good chance that your engine bearings are worn and need to be replaced. Rod Knock: Worn Bearings. Loose Ball-Bearing BBs Loosen the lock ring on bottom bracket with lock ring tool. Could also be a main bearing, but that is also more commonly associated with low oil pressure. One at each end of the crankshaft. Main Bearing Noise. Today’s hi-flow, aftermarket, CNC-ported cylinder heads, high lift killer cams and induction system power adders (blowers, turbos and nitrous) are making more power than ever before, and really hammering the bottom end of the engine. … Damaged or worn main bearing noise is revealed by dull thuds or knocks which happen on every engine revolution. The upper part of a main bearing, commonly has an oil groove on the inner surface. The first and most common reason for mountain bike creaking occurs when the bottom bracket bearings start moving around in the frame with each pedal stroke.. T ... however this serves as a reminder that wheel bearings can in fact be the culprit in our cars mistaken by road noise. Main bearings support the crankshaft in the engine block. However we pulled into car park and heard what was like faint knocking at idle and when revs drop, good friend who is a mechanic said that sounds like bottom end. As the pistons travel up and down in the engine, they turn the crankshaft which ultimately sends power to the wheels. Amazingly, there was no scoring or scarring, and all parts checked within limits. i did a top end, carb clean yada yada and it fired right up. This noise is loudest when the engine is under heavy load. I just lit it off for the first time (started first kick! The noise has been steady for at least a year before the replacement now it rides like factory again :yes: Jump to Latest Follow 1 - 12 of 12 Posts. With pin spanner, turn the adjustable cup clockwise until there's no more play, but no binding in the bearings. it runs fast and nothing feels wrong with it, just a noise at idle that sounds like the crank bearings. A spun bearing will make a nasty bottom end knock that might come and go a mite. The rod bearings facilitate smooth piston movement, but they can become worn out or come out of position over time. 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