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Yamaha 50 bottom end seal

C

Colin Thomson

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" Wonder if someone can help.

" Wonder if someone can help. Think I have identified the problem, Cyl 3 doesn't fire until engine is run up to max rpm. Ignition and carb OK but unburnt fuel shows on water surface at the stern when idling.
Assuming I'm correct and the bottom end seal is leaking the charge away, are there any special tools required to strip down to, remove and replace the seal? or can I get at it with normal sockets etc? "
 
"Colin,

You can do this job


"Colin,

You can do this job with standard tools.

"
 
" Tony,
thanks for the info.


" Tony,
thanks for the info. Meantime I got the seals and gaskets and did the job with standard tools. When I got to them, both the drive shaft seals and the Main Bearing seal were badly worn, so I was convinced that was the solution.
However, when I started her up, same problem, Cyl 3 not firing until high rpm is reached.
What I notice :

The cooling water from the prop is very milky, smells strongly of gas.

The cooling water tell tale jet is clear, no milkyness or gas smell.

Subjective compression test indicates all cyls very similar.

There is no indication of water in the cylinders, all plugs wetted with gas but clean.

The engine will start and idle happily on cyl1 only or on cyl2 only. With cyl3 ignition only connected, the engine will fire and run unevenly and briefly only with open throttle and choke. There is a spark to all cyls. Switching coils doesn't move the problem from cyl3

So what I now start to wonder is if there is some failure mode of ignition system that could result in the timing of cyl3 only being way out.
Any ideas? The module or the flywheel sensor? Or ANY tips that might help.

Rergards, Colin. "
 
" i don't know what i am d

" i don't know what i am doing, but was told to ask for a 1989 manual for a yamaha 50 "
 
fuel pump gets its vacumn fro

fuel pump gets its vacumn from bottom cylinder and if the diaphram has ahole in it the bottom cylinder will load up and foul out at low speed
 
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