2012 KX 450F cam chain tensioner failure/ damage done

I recently discovered I have been riding my KX with a broken tensioner. Before the discovery the bike rode and sounded fine except for the rattling of the cam chain which I couldn't hear all of the time. I installed a new tensioner and fired the bike up and it started to make a horrendous knocking noise. The first thing I expected was a stretched timing chain. I installed a new chain and piston @ 60 hrs on engine. I inspected the valves as well. They are in spec along with the timing. When I started the bike after rebuild it still made the noise! There is some shavings in the oil as well. Bad crank bearings? There was no up and down play in rod either. All electronics seem to be working the orange light doesn't stay on. Any help would be greatly appreciated!!!

Sounds like your timing is off.

does it make the noise when idling? Or only under a load when riding?

Edited by skthom2320

The timing is correct for sure. I haven't rode the bike since it started making the noise. It starts very easily and revs fine. I don't let it run for long.

Does anyone know how to tell if the intake cam sprocket may of spun? It seems to be pressed on. The lobes line up at TDC like the manual shows facing outward from each other. Also will these bikes run with bent valves?

I tore the bike down today to discover valve marks on the intake side of the piston. I am timing the bike according to the service manual. 29 pins and lining the cams up at TDC. Since the bike had tensioner failure, I wonder if it wore the chain guide too. I'll figure that out tomorrow. ImageUploadedByThumper Talk1377565159.936272.jpg

ImageUploadedByThumper Talk1377564912.161202.jpg

Just my guess but, I bet when the first tensioner broke your cam chain jumped time and your valves hit the piston, lucky you shut it of and found the problem and replaced the tensioner and the chain.

I did the same thing with mine, heard a noise, after much head scratching discovered the cam chain was junk and not changed with the last top end. I fixed it but i still sometimes second guess myself thinking its gonna grenade.

Been running strong for 4 months now. I have some YouTube vids up if you search 11kx 450 weird noise to compare.

Edited by ryanthesailorman

Thanks guys for your help it was the timing after all. One tooth off some how!!!

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