Yamaha 1996 F50 (4stroke) Idle problems

[Craig from Jersey CI]

Hi guys, hoping you may be able to help?

I have 2 problems that may be related.

1. The engine stalls at idle / low revs trolling.
2. The engine will often rev high when taken out of gear and back to neutral.

When it goes to stall it's like a throttle reduction rather than a 'cough and splutter' if you know what I mean?
The engine has fresh fuel.

Any thoughts would be greatly appreciated.

Cheers
Craig

 

[Craig from Jersey CI]

Re: Yamaha 1996 F50 (4stroke) Idle problems

Well, they say with these things you should start with the obvious.....

Swapped and then cleaned up the plugs today and it seems to have sorted it (the idle part). No idea on the high rev thing after being in gear.

I did make an interesting observation though....
My idle screw is fully backed out. My idle revs are in effect being set by the balancing screw on the top carb. If this screw is backed off there isn't enough spring in the carb returns to bring the carbs back to closed. I don't understand why the carbs would have lost their 'spring'.

Although the engine is getting on a bit now (1996) it's been well looked after and hasn't been used excessively / commercially.

Any thoughts as usual are much appreciated.

 

[rodbolt]

Re: Yamaha 1996 F50 (4stroke) Idle problems

sounds like the linkage adjustments need to be done by someone with the factory manual and a 4 channel manometer. especially now that ya dinked with it.
the upper three carb shutter screws are not idle screws.
only the bottom carb has an idle screw.
most likly the carbs are dirty.