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2018 BF100A How much valve noise is normal?

T

Tangotoo

New member
Just finished the heads and install on my BF100A and she is running beautifully! However, the valves have more rattle to them at idle than I was anticipating from a late model four stroke outboard. I put the engine through a few thermal cycles before setting the valve lash and the nice didn't improve. I'm confident in the build and the valve setting, all the VTEC arms tested functional.

It's probably quiet enough that when I put all the covers on I won't notice it, but I just wanted to get some input from fellow owners on what theirs sounds like at idle.

0.010" per the book is quite a bit of lash on the exhaust side, maybe it'll quiet down once the engine is hot and everything has expanded.
 
There should be no valve noise at all. .008 and .012 is usual clearnce.I work on these every day and can tell you you should not hear any rattle. Are you sure it's not injector pulse, otherwise timing chain ?
 
iang6766 said:
There should be no valve noise at all. .008 and .012 is usual clearnce.I work on these every day and can tell you you should not hear any rattle. Are you sure it's not injector pulse, otherwise timing chain ?
Click to expand...

Thank you for the reply iang6766. I don't believe it's timing chain because I hear it primarily from the #4 cylinder area of the head (opposite the timing chain). The VTEC solenoid is in that area, is that a noise source at idle? I don't think it's injectors because the sound isn't consistent, it has more of a resonant quality to it were it has a slight tapping sound at idle, then clears after increasing a few hundred RPM, taps again at a higher RPM and is gone by 10-15% throttle. It has the sound a loose washer would make if it was vibrating on a metal surface. I'm beginning to wonder if detonation from clogged injectors may sound like light tapping? It's definitely not a knock, or hard metal contact.

Thanks again for your input, I have a lot of wrench time on two strokes and Mercruiser/OMC, this style of engine is new to me. Although, I love the similarity to my Honda autos.
 
Oh, I get you now. The noise you're hearing is the mechanical fuel pump, most obvious once the fuel system is fully primed and the pump goes into a loaded mode, gives a light tapping noise, hold your finger on it andcyou will feel. Yes, this is normal
 
Thanks iang, does the oil pump experience the same by rattle under no load? I spent a lot of time with a stethoscope last night and isolated the intermittent tap under no load to the oil pump. I removed the pump and it looks immaculate inside. Nothing appeared worn or loose. The little thrust washer at the interface of the cam output drive made me wonder if it could rattle when there's no thrust force against it. I'm going to finish putting it together and see what it does on the water.
 
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