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Loud knock

2K views 38 replies 6 participants last post by  Panici 
#1 Ā·
R6 had a small tick sound which turned into a loud knock here are some videos of it. The bike sputters and would die while idling i tried riding it a few blocks to someone's house but then it started making it a worse noise.


Any help is appreciated.
 
#34 Ā·
Bottom end may have taken damage.

Even if the crank bearings look fine there could be hidden damage to either or both piston rings, rod, skirt, etcetera.

This engine turns near 16,000 RPM. That's 266 up AND down motions occurring over ONE second! It takes 0.00375 second for that up AND down stroke... 0.001875 of a second for just the up or just the down. The forces are unimaginable. If there is any damage, defect, it will come apart and that engine (between your legs) blow up.

My OPINION is, gotta do it right or don't do it at all.
 
#35 Ā·
Yea when I saw that kind of damage I figured it would be toast and there would be a lot more stuff that needed to be replaced. I think a new engine is the best way to at this point but there pricy but then again it would probably cost the same to rebuild it. If i could find a new head for a cheap price I would consider it but I cant find one anywhere and a new one is about 1500 not including new valves.
 
#36 Ā·
To cut costs, could just do cylinder three? Some research would reveal whether or not that would create complications; such as an unbalanced engine. Sometimes metal bits from a failed cylinder end up in the adjacent cylinders. That could be the case with cylinder four? Would have to look more closely than the video allows. That would be another cylinder to redo.
 
#37 Ā·
Cranks and big end bearings can handle a lot. How light are the yamaha rods? I haven't heard of any bending, short of major catastrophic events. If the rod is fine, and piston can be sanded to get the high spit off, worry about the head. Guides get mangled when valves do the pretzel dance. I would pay the shop to diagnose all the valve conditions. Probably $100 and you will know the bill of materials. Expect minor seal leaks on every valve. That is life as seats wear in and deform. A seat grind isn't much, and you would have to do the one seat minimum, and stem grind a replacement. Get the pro diagnosis. Then consider a full rebuild, used head, new head, whatever before spending more money.
 
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