1999 F50TLRX Noise

[ChuckB1954]

I did all the fine tuning on my recently installed carbs, other than the synchronizing and for the first time I heard this unknown noise. All I have done to this engine was to adjust the valves and replace the carbs. Never heard this noise before.Here are some videos. Hopefully someone can tell me what is is. I am willing to accept the bad (or good) news.

[ChuckB1954]

[ChuckB1954]

[ChuckB1954]

[robert graham]

Sounds almost like an intake/silencer sound....maybe run the motor with the silencer removed to try to identify source of sound?

[99yam40]

popping back into the intake maybe.
seems pushing on the front made a difference
might try redoing the valve adjustments.

did you have to do a lot of adjusting to them ?

did you try a mechanics stethoscope or long screwdriver to your ear to see if you can find a sorce

[ChuckB1954]

Sounds almost like an intake/silencer sound....maybe run the motor with the silencer removed to try to identify source of sound?

I would have to pull the carbs off again and use spacers. The silencer is an critical part of the assembly.

The silencer has always been on there. This noise just started today. I mentioned in another thread that I could take the flywheel(crankshaft) and rock it slightly back and fourth indicating play in the small or big end. I asked it it was normal but never got a solid answer. Was told basically to not worry about.. Jut put the boat in the water and run it. Maybe it is showing up now because the carbs aren't synchronized?? Maybe I am jumping the gun though.

[ChuckB1954]

popping back into the intake maybe.
seems pushing on the front made a difference
might try redoing the valve adjustments.

did you have to do a lot of adjusting to them ?

Not really.. I should have left them alone, but I did adjust them in the middle of the range and did a careful job since I had already took the cover off.

[99yam40]

thinking about it more, could a 4 stroke pop back thru the intake due to lean cylinders?
I do not think so.

I guess it is time for a leak down test to see if all of the valves are seating properly.

hope a valve did not hit a piston or valve sticking in a guide

[panasonic]

Sounds like some loose in the intake box or somewhere else on the engine..not an engine knock. It seemed to have stopped in one of those videos briefly.

[ChuckB1954]

thinking about it more, could a 4 stroke pop back thru the intake due to lean cylinders?
I do not think so.

I guess it is time for a leak down test to see if all of the valves are seating properly.

hope a valve did not hit a piston or valve sticking in a guide

Maybe I should check the valve adjustment again.. it's a pain, but it only takes about 1/2 hour. Only thing I messed with other than the carbs..but, I know they are correct.. plenty of play.

Sounds like some loose in the intake box or somewhere else on the engine..not an engine knock. It seemed to have stopped in one of those videos briefly.

I will consider that and do an inspection. When I block the opening with my hand as shown in the video #3, it seems to stop. I sure pray it is not an engine knock.. thanks for the hope.. maybe I should put the kool aid away!

[99yam40]

maybe it is a screw from the throttle valve to shaft that is beating on the top of piston.

only 2 things were done carbs and adjusting valves, take your pick

[ChuckB1954]

maybe it is a screw from the throttle valve to shaft that is beating on the top of piston.

only 2 things were done carbs and adjusting valves, take your pick

No way..Could never happen..

[99yam40]

Bore-scope just to rule out the pistons hitting something inside the cylinders.

you have to wonder why those carbs were sold
someone parted out a motor due to some bad thing happening to it.

Did you go thru the carbs before installing on your motor?
was this the 1st time the motor was started with these carbs?

I found out My C40 closed up the gap on #2 spark plug last week.
not all of the way, but it started an erratic miss firing .

I will run it out on the water today after cleaning and regapping the plugs.
I may need to find a bore scope and inspect my cylinders also

[TownsendsFJR1300]

I'd pull one plug wire at a time (ground to engine) and see if the noise lessens...

That noise is too regular and sounds as if it's being amplified thru the air box..

And nothing would last that long bouncing around the combustion chamber..