Yamaha 421 STI

[AndyMicklewrigh]

Anyone know how to fix a Yam 421 revving to maximum while in neutral
As soon as it starts, revs quickly increase until I turn it off on the key
Rev counter appears to have stopped working simultaneously
Any advice appreciated

Thanks
Andy

[beamishken]

Have you checked the throttle leaver on the pump isnt stuck?

[Brian]

Not had this particular problem, Andy, but......
if the throttle was open wide when you switched off, maybe it has now snapped/broken? thus leaving the engine in full go mode when you restart.

[AndyMicklewrigh]

Cable is ok
Throttle mechanism appears to work fine
Seems like something inside the main pump is stuck in the wide open position
I must have done thousands of miles on this type of engine/ pump with no problems before
Just limped round from BRIXHAM to Dartmouth on one engine in F5-7 but it’s in the river now ready to be lifted for the winter
Annoying thing is I can’t get max revs when I want to
LOL

[beamishken]

Sounds like time to take the pump off not much else will give you full rpm and allow you to still switch off. so more than likely an internal pump fault
Fortunately the pump is relatively easy to get out assuming you have access in the engine bay

[redrubber xl]

It’s the pump I had same problem with my 422 thy don’t like low sulphur diesel you need to put oil it .