99 Yamaha 40HP 2 Stroke - Noises at low rpms (Video)

[tmetzzz]

I have a 99 Yamaha 40hp that makes a grinding clanking noise at low RPM's. I recently replaced water pump and took lower unit out and the noise continued. It sounds like something on the top of the motor with the flywheel would anything throw it off at low rpms but when run at higher rpms grinding clanking noise goes away and motor runs like new?? Compression 110 across the board. Strangest thing and it has me stumped, any help would be greatly appreciated! Thanks!

http://youtu.be/nVmtBPcKteY

 

[99yam40]

main bearing on crank could be the problem.
Mine did not sound that bad , but 3 out of 4 were real rough when rolled by hand when I got the crank out

Rust from water intrusion is what I was told caused it

 

[robert graham]

Or it could be paranoia/all in your imagination....my C90 rattles and clanks some at lower RPM's....maybe it's just the old 2 stroke motor noise?....

 

[tmetzzz]

main bearing on crank could be the problem.
Mine did not sound that bad , but 3 out of 4 were real rough when rolled by hand when I got the crank out

Rust from water intrusion is what I was told caused it

I just did the TDC check to check my bearings / gudgeon pin and all checked out perfect.

Using a wood dowel I moved the piston to the top of the stroke and pushing trying to move the piston but none of the 3 would move, figuring my bearings are still tight and good shape from this easy test. It must be a magnet or something in the flywheel?

The motor was running great then after half way during the trip it all of a sudden started making this noise on the slow down coming off plane and has been making it ever since? I can deal with it, but it's knowing something's going to break at some point I don't want to be stranded if I can fix it.

Another video of the motor, excuse the cold start....
http://youtu.be/E9rCI7nMwL4

 

[robert graham]

Look around under the cowling for a bracket or fitting that may be rattling....tie-wraps are very helpful to secure things under there....

 

[tmetzzz]

Look around under the cowling for a bracket or fitting that may be rattling....tie-wraps are very helpful to secure things under there....

Well bad news now is that I can not get the motor started at all, it turns over fine but will not fire up seems as if I have plenty of fuel getting in (primer bulb) so I replaced the spark plugs and checked spark in all three wires, everything is good there. I've checked the kill switch and ensured it wasn't engaged.

Seems as if it's one thing to another right now with this, im assuming the next step is to rebuild the carbeurtors and start from there?

40MLHX 40 Hp