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I have a Yamaha 90hp 2s (specifically a 75CETO upgraded carbs to make it 90hp) however I've noticed a very obvious ticking or knocking sound when in idle, and when in gear but less audible.
It seems like quite a distinctive noise, I've tried looking up the issue, some have suggested piston slap, others spark issues, dirty or improperly fuelled carbs etc, but I've not quite managed to find a sound to match the issue from videos of others engines. I also checked the spark plugs currently in the engine and they are NKG BR8HS-10, the service manual says they should be B8HS-10 although this is contradicted if they have noise suppression? Haven't had an opportunity to remove the current plugs could it be its only running on two cylinders?
Here's a video of the engine at idle,
https://youtu.be/0DeJeGIJaps
It also has an inversion kit on it designed to allow the engine to continue running after a capsize, no idea if anything to do with this would contribute to the issue?
Thanks in advance for any advice
It seems like quite a distinctive noise, I've tried looking up the issue, some have suggested piston slap, others spark issues, dirty or improperly fuelled carbs etc, but I've not quite managed to find a sound to match the issue from videos of others engines. I also checked the spark plugs currently in the engine and they are NKG BR8HS-10, the service manual says they should be B8HS-10 although this is contradicted if they have noise suppression? Haven't had an opportunity to remove the current plugs could it be its only running on two cylinders?
Here's a video of the engine at idle,
https://youtu.be/0DeJeGIJaps
It also has an inversion kit on it designed to allow the engine to continue running after a capsize, no idea if anything to do with this would contribute to the issue?
Thanks in advance for any advice