F80 Backfiring and Shaking at Idle

[madharchod]

to Mitch
people who drink kava here in FIJI dont get anything done mate they just think
and all your jargon it will help in your future endeavors i have 42years experience in this field ,now retired so can teach you a thing or two buddy ,nice try
cheers

[rodbolt17]

if you listen you can learn how magic air can make 15 HP with no added gasoline and how magic spray can penetrate fuel bowls and clean jets and passages without carb disassembly.
I have better than 30 years experience, many many schools 6 yrs in the USN's advanced electronics field and I am not retired yet and do this stupidly simple stuff everyday.
if there was a shortcut I usually would find it as I am rather lazy.

for the past 25 yrs or so I work commission/flat rate and typically out earn most techs in not only the shop but in the area.

which means if its a comeback I don't get paid the second time and if I order a part,say an ECU, and its not correct I buy that part.
I don't own any spare parts.

I was among the first 14 or so Yamaha master techs in march of 06.

master tech program started in 06 and if you look at the website there still are not many for a program that started almost 8 years ago.

its a tough test and even my service manager failed it.

[madharchod]

hey chief
if you have been in this **** for so long as i have then you would understand there are some tricks of the trade that is never let out ,its only to your successor ie your son who takes over from you ,and in my case it has been my son ,you may have been to tech in 2006 but mind you i was in design and manufacture of these motors when they were owned by OMC in Mexico in early 1970 and i basically graduated from uni and straight into CAD CAM production which led to basically be with OMC for ten years then i was offered a better contract with Yamaha in Japan where i stayed for another 5 years developing this oil injected models and earlier four stroke concept ,later i started my own workshop and trained people and worked and retired now ,basically i dream about this motors day in day out in my sleep ,but a time comes when one has to lay his leg up and concentrate on other good things in life like cruising the pacific and enjoying another way without getting grease on hand and worry about opening up and rude customers or some tight-butt who wants to get things done for basically free like some on these forum
cheers

[99yam40]

you still cannot explain how you clean jets and passages inside the carbs by spraying stuff from the outside of carb or how you can create hp by just adding air

Just makes your posts more BS

[mitch]

So please explain how start ya bastard is going to clean carbs .............. your delusional .

[madharchod]

you guys are so eager to learn ,i will tell you one day let me stir you people for a little as knowledge has to be passed to somebody who will be using it ,but rushing it like child wanting candies ,let me relax and think about it as iam on my way to OZ in my cruiser so when i get there maybe i will let out some of my trade secrets to you apprenticeship
till then cheers

[mitch]

Madchops

Its ok I have contacted the chief in your village in fiji he said all is forgiven they just want thier village idot back
The chief said that you must stop playing with the tiller

[mattro51]

OK so I cleaned all of the carbs very thoroughly. I took each one apart and cleaned with carb cleaner and compressed air. . Then I then replaced and synced per the service manual. The sneeze still persisted. I can "feel" the change in vacuum pressure in the line leading from carb 2 to my manometer during the "sneeze". On a hunch I adjusted the pilot screw out on #2. The sneeze stopped but the vacuum pressure increased substantially placing it significantly out of spec. Could carb 2 still be clogged? Any input is appreciated.

Thanks

[99yam40]

I would think that if giving it more fuel would mean that something is still plugged on that carb.
Might need to have it cleaned in sonic bath

[almetelo]

Not always carbs can be properly cleaned at 1st attemp

There isn't a standard value for vacuum pressure.
You just need the 4 carbs with same vacuum.

do you have pre-fuel filter with water separator? did you clean the fuel lines or the fuel tank is cleaned?

Good luck

[mattro51]

I took # 2 off again and cleaned tonight. I do have a question though. The large main jet leading from the throat of the carb to the bowl, is it removable? Looking at the construction I cannot tell and I don't want to start pulling on something that isn't supposed to be removed. If it is removable what is the easiest way to remove? Almetelo I do have a prefuel filter and water seperator. I cleaned the filter, replaced the seperator and the fuel lines prior to digging into the carbs. Thanks for your response.

Thanks

[almetelo]

Yes, main jet is removable as slow jet, jet needle and other parts.
Also remove the 4 top screws to access those little holes.

[almetelo]

Hope attachment can help you

[mattro51]

Part 13 in that diagram is the one. How do I go about removing it? The only way I see is to use a pair of needle nose pliers and pull it out. I tried that but it won't budge and I don't want to damage it. Is there any way to push it out from the throat side?

Thanks

[mattro51]

So I took # 2 off again, disassembled completely including the slow jet and cleaned with carb cleaner and compressed air. I don't have a sonic bath so that isn't an option right now. After reinstallation I still have the same problem. I have noticed that during the "sneeze" the RPM's drop significantly and then return to normal. All of that happens over approximately 3-4 seconds. Is there any chance that the float could be sticking? I did operate it during disassembly and it seemed to be working properly. I also pulled the spark plugs, each of them looked good. Down side, I still have the same problem. Upside, I'm getting real good at taking carbs on and off.....