Yamaha 200 OX66 not shutting down clean

[fishn_man]

Does anyone know what would cause the motor to not shut off immediatley when you turn the key off. Mine does not shut off immediatley, but it kinda coughs then sputters and shuts down. Kinda like the old carborated cars when they were out of time and would deisel when you would turn them off.

Any help???

 

[rodbolt]

Re: Yamaha 200 OX66 not shutting down clean

mmmm, good one
what is the idle speed in nuetral?
when was the last decarb ?
what is the full model number of the engine in question?

 

[fishn_man]

Re: Yamaha 200 OX66 not shutting down clean

what is the idle speed in nuetral? Approx. 850RPM
when was the last decarb ? Never, I run ring yamalube and ring free.
what is the full model number of the engine in question? VX200TLRY

Talked with another mechanic today and he said to mix some Mercury Quickleen in the gas to decarbon and give it a four or five mile run. Should see a big difference.

What is your opinion please?

 

[rodbolt]

Re: Yamaha 200 OX66 not shutting down clean

your idle speed is a bit high, try a careful link and sync to insure the throttle shutters are full closing and the oil pump link rod is adjusted correctly as well as the TPS voltage is correct.
the VX indicates its a Vmax OX66 it also tells me by the Y designation its a 2000 model which would be a 3.1L engine.
Vmax OX66 motors did NOT use CCS so they are very touchy on linkage adjustments.
also carefully check all ECU grounds and the ground lead going to the keyswitch.
when switched to off the 12V for the fuel pump and injectors and ECU is removed and the ign system taken to ground.
have you tested the lift pump diaphrams for leakage or the injector rail pressure for a possible leaking injector?
spec for idle speed is 730 plus or minus 30 RPM, typically we see closer to 650 RPM so 850 is a tad high.