Help guys Yamaha 50 4 stroke carburetor

**skydog** · 04-24-2018, 08:47 PM

The motor has like zero hours on it like new shape. Out of no where it started running real bad at lower rpm. It will hardly run? Upper rpm is perfect, so I thought dirty carbs for sure!! So I took the rack of carbs all apart and cleaned them big time. Put all back together zero change. Is there a low speed stator? Any know problems with this motor? Help please!!!

Thank you Skydog

**Capt.Insane-o** · 04-24-2018, 10:41 PM

did you remove and clean the pilot jets?, and synch on these things can be a bitch, carefully drill a small hole in the brass plugs covering the idle mixture screws and pry them out. if you've never worked on these just take it to someone with a vacuum mate because you'll never get it right.

**skydog** · 04-25-2018, 08:06 AM

I bet you are right I did not!! It is lean sneezing out of the carbs at low rpm. I was 99% sure no fuel down low!! They are under some brass plugs?
Thank you so so much!!! P.S. Man if I knew all this I would have efi all day!!!

**Motv18** · 04-25-2018, 12:27 PM

That’s not the ones they forgot to hone the bores and scuff is it. I don’t have my years clear on those. Pretty much check every Yamaha these days.

**racervboat** · 04-25-2018, 02:41 PM

Cappy right the pilot jets are the small ones under the rubber plugs in side when you take the bowls off.If you drill the brass plug for the mixture screws use a left hand drill bit seen many people drill right through and the bit grabs the screw and snaps it right off oops carb junk now .I got so good at syncing these carbs I don't even need a vacumate Like cappy says they are a bitch if you never done one your screwed take it to a dealer period.

**skydog** · 04-25-2018, 03:30 PM

Thanks for the help guys! It was a plugged pilot jet. I even used compressed air and carb clean not good snuff. I Isolated it to what cylinder and worked on that carb perfect thank you guys!!

**racervboat** · 04-25-2018, 03:38 PM

Good for you,ya got lucky.Use a good fuel stabilizer all the time and non oxy fuel if you can get it in your area.Those carbs get plugged up really easy most always the pilot jets.

**Capt.Insane-o** · 04-25-2018, 04:10 PM

I put my customers on the marine stabil with those carby fourpokes. It cut the bull**** down to a dull roar.

**skydog** · 04-26-2018, 09:24 AM

Will do thank you! If it happens again i will drill them out a touch, (WOW SMALL) that damn low emission wow they run them lean!!! If you stab the gas from idle there is not enuff fuel to keep up. She will lean sneeze out of the intake and stall smh I know there is nothing wrong other than super lean jetting....

**Capt.Insane-o** · 04-26-2018, 09:47 AM

There were so many complaints from throttle dumpers when they came out. A factory rep was in the shop and I was having my way with a set of 90 hp carbs to satisfy a customer, he freaked out when I got out my pin reamer set and pulled the plugs out of the idle mixtures. In a not so polite manner he was informed that if they sold motors that actually ran we wouldn't be standing here right now and to go bother someone else..

Couple hours later we had a 90 that would pull up a skier, not ding off the rev limiter because the last place band-aided it with too small of a prop and it's over all running qualities improved.

**racervboat** · 04-26-2018, 10:15 AM

Remember when they first came out and would run like crap,you had to drill the plugs out and richen the mixture screws.When the rep was in the shop he freaked out and said all you mechanics doing this can be sued by the epa for tampering kind of like taking off a catalytic converter on a car.They even told us that in yammy school but never heard of anyone sued? But if we didn't customers were lined up in the lot with boats that ran like chit and they were not a happy mob.

**Capt.Insane-o** · 04-26-2018, 10:43 AM

Ahh the good ol days, the debut of optiflops, fucht injection,Half Detonated Piston Infection, four strokes that wouldn't pull a limp dick out of a lard bucket. Pissed off customers in every corner...... Then a 1958 7.5 Evinrude would come in for a 25 year tune up and I'd praise the ground it sat on.

**skydog** · 04-26-2018, 11:07 AM

Idle air screws should I just back them all out like 1 full turn?
Thank you

**racervboat** · 04-26-2018, 11:44 AM

Start with half a turn exactly on all carbs after that and it starts to run chitty that's when you get in trouble cause it starts to screw up the sync & link but it may just only need 1/2 or one turn out to loose the bog or sneez the are very touchy.