Low End Knocking When First Starting Motor

[twr1776]

I have an 81 1000L I got used with 11,000 miles and not on initial start up but after approx 10 - 15 seconds I have a mild knocking that seems to be coming from the upper right crankcase area. It goes on for about 15 - 30 seconds and I will gently take off and then the noise will stop completely. This only happens when I have not ridden it for a few days. After the initial cold startup this sound does not happen again. It also does not usually happen the same day if I have ridden it earlier in the day or does not make the sound at all if I make a short stop. I have switched to the Rotella Synthetic with no change in the pattern of the sound. Once warm the motor runs strong and quiet with no oil consumption. I think I may have a partially blocked oil passage or partially blocked oil screen and am planning on dropping the pan over the winter to clean the screen. From the other posts on this site I do not think trying to flush the motor is a good idea because of the lack of a safe flushing material. Any suggestions on other items to check? Thanks for any suggestions.

[chef1366]

Check torque on your clutch nut.

[Road_Clam]

I have an 81 1000L I got used with 11,000 miles and not on initial start up but after approx 10 - 15 seconds I have a mild knocking that seems to be coming from the upper right crankcase area. It goes on for about 15 - 30 seconds and I will gently take off and then the noise will stop completely. This only happens when I have not ridden it for a few days. After the initial cold startup this sound does not happen again. It also does not usually happen the same day if I have ridden it earlier in the day or does not make the sound at all if I make a short stop. I have switched to the Rotella Synthetic with no change in the pattern of the sound. Once warm the motor runs strong and quiet with no oil consumption. I think I may have a partially blocked oil passage or partially blocked oil screen and am planning on dropping the pan over the winter to clean the screen. From the other posts on this site I do not think trying to flush the motor is a good idea because of the lack of a safe flushing material. Any suggestions on other items to check? Thanks for any suggestions.

They call that a "dry rap". It usually signifies a excessively worn lower end crankpin bearing(s). It's far more common in automobiles. The reason the knocking deminishes over a short period of time is the pumping oil is filling the excessive gap. I would take it to a dealer who can perform an oil pressure test for another opinion.

[twr1776]

Thanks for the advice, I will check both suggestions. With the low mileage I wouldn't expect to have the wear but I suspect the bike sat somewhere for a long time and that is not usually good for motors. If the bearings are the culprit would it be motor rebuild time or should I just run it. Thanks

[flyingace]

These are roller bearings, so 'dry rap' does not apply. If the bearings knock they will always knock. You can check your rod bearings using a pencil or dowel. Just remove the plugs, rotate engine until the piston is just past TDC. Then push down on it from the plug hole. Any detectable downward movement means a bad bearing.

Since you are going to remove your oil pan anyway, you can check your mains then. See if there is any noticable play in the crank. Any movement is a bad sign. You can also look for metal shavings in the oil pan. These are the result of worn bearings.