heavy knock

I have a 1981 kz550c ltd last week i rode the bike about 15 miles no power loss or anything then all of a sudden there was this loud knock on decelaration it went away and then after about 5 seconds started again. bike starts no problem just a loud knock now can any one tell me what this is

Post edited by: Pijoe1, at: 2007/07/22 09:14

Can you give more information?

1. Check engine oil level- does it have oil?
2. Do you smell engine overheating, oil smoke, etc.?
3. Does it keep knocking at any rpm?
4. Does it sound like it's coming from the engine or maybe a loose exhaust or other part?

yes it has oil and it knocks at any rpm it also was not overheating neither it just suddenly started it is coming from the engines left side!!!!! please help me i have invested alot in restoring this bike there is not anny smoke coming from exhaust

Post edited by: Pijoe1, at: 2007/07/26 20:12

If it does it at idle, use a long screwdriver or wood dowel like a stethescope, just hold the driver or dowel up to your ear and the other end on different parts of the engine until the noise is the loudest, and see if you can pinpoint the area it is coming from.

Knock? Why is this in the carb section? Should be an engine issue, I would guess. Does the 550 have rods that are removable? BTW: Harbor Freight has mechanic's stethescopes that are pretty reasonably priced and one of these will probably work better than the screwdriver trick if you really want to hear inside the engine. Finding the source of the noise would be helpful in diagnosing... could it becoming from the countershaft area? Bottom of engine? Top of engine?

the sound is coming from the left top side of engine::::::::::

Take your valve cover off and have a look. I can't think of anything that would knock in the valve train but that is the only thing at the TOP of the engine. If the knock is from the cylinder block, then it might be a rod or rod bearing. The two places are about a foot apart and that is why it was suggested you use some means to be more specific as to location... diagnosing is only as good as the info you diagnose from.