Re: Water Getting in Top Cylinder Yamaha 40hp Twin

[joesnuffy]

Thanks Guys,

The cages indeed are made from plastic on those large rod bearings not a good feeling. I put 2 brand new OEM ones in it one for each rod when I rebuilt it.

What I make out about the original engine failure was the rod bolt/s backed off the rod and slapped a hole in the front of the engine case. I purchased the boat and motor after the failure. The motor looked to have been barely used very clean for that year no oil leaks etc no overheating paint looks new. Originally I thought it might have just spun a bearing do to long storage time but after I disassembled the engine the rod bolts were backed off on the top cylinder.

I am going to take the carbs back off today and hope that the screws on the upper reed block are intact and not damaged which will mean that the rod is working as it should I will then order a replacement reed block assy. The one on the ebay auction I was using as a comparison to show the screw had been getting tapped a bit by what I think would be the rod and your right it is rusted and it wouldn’t work for my application. Their are several one’s on ebay right now that look to be OK. I did use locktite on all the screws even the ones that hadn’t backed off yesterday I didn’t do the ones that hold it to the plate I will do them when I put the different reed block assembly on.

I will also perform a compression check today and check my notes on what it had after about 10 hours of run time.

I did check to see turning the flywheel by hand yesterday to see if I could feel rod tapping the reed screws and I did not feel it. But your right if the screws were tapped today I will be going to see yamaha. And I will put new gaskets on they might even be thicker than before that is something yamaha could tell me and I could micrometer them and compare the thickness of the old one to the new one and know that the new one will get squashed a bit. I do know when I have built sea doo 2 strokes the base cylinder gaskets come in different thicknesses to get your piston to head clearance correct.

I appreciate the help and will keep you posted.

Joe

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