1998 20hp Yamaha backfires at idle?any fixs?

[voity82]

Hi everyone, Got a 20hp Yamaha 20hp 98' model on my 12ft quinny but it backfires at idle which stalls it. When you idle the outboard it backfires every 5-8seconds and this stalls itself. Is there any fixes people know of or maybe wat is causing the problem? Its a pain everytime I idle to pick the crab pots it dies after idling for 20seconds.

Any info would be great!

Thanks voity

[trueblue]

Have you had the carby off recently? might be the idle jet clocked up with either oil sludge or crap.

or, is it too lean?

is it a real backfire, or a birp and fart that stalls it???

cheers

[Roughasguts]

If it's more a sneeze, than back fire, clean the plugs with carby clean, or just replace them.

[FNQCairns]

Try adjusting your idle circuit, it will be the only screw that is adjustable for the fuel proper. Back it out 1/8 of a turn anticlockwise each time, mark where you started. It will come good assuming that is the only bit you touched or did touch.

cheers fnq

[voity82]

Hey guys thanks for the info, it is probably a mix between a cough and a backfire certainly shoots the smoke out alot further when cough/backfires running on the hose. I will try cleaning/ regapping plugs then will try carb adjustment then if all else fails I will remove the carbs. Does anyone know where the stock carb needle is meant to be ie 1 turn out from seated?

p.s I have never had carbs off I have just cleaned the plugs apparently the guy I bought it off nly used it once a year so sludge could've formed in the idles jets maybe will give it a blast of carb cleaner.

[trueblue]

From what you've just said, I think its almost certain that you have to take the carb off and clean out the jets. Classic symptoms of a clogged idle jet.

Cheers

Mick

[mark221263]

I'd 1st check snycronisation between carbs, throttle and ignition timing.

Once there adjustsed check idle mixture, not sure about the 20hp but the No of turns will be in the w/shop manual. For the 3 cylinder units it use to be 1&1/4 turns.

If this does not improve things them I would strip and clean the carbs. If is more of a sneeze than a backfire it ssounde like it is running lean which coul dbe either bad adjustment or a blocked jet or blocked fuel idle passage.

Make sure you have a decent fuel filter fitted. Also if it is the idle jets you may stork them out by taking the screwss right out, give them a blow through with carb cleaner and the fine plastic tube and then trying again with the correct setting. Beats stripping them right down.

Best thing is to spend the $60 and buy a manual, then work though things easy one first.

Cheers Mark

[voity82]

Thanks guys will get on it tomorrow and find out whats going on.