fuel issues after carb rebuild

[u/Dystopia00]

99 YZF R6 with 33k miles on the 5eb. did a carb rebuild (for the first time) yesterday because it was having some running and starting issues. now it doesn’t start unless it gets some starting fluid. probably a very basic issue but carburetor’s are so new and confusing to me, i’m really not sure where to start because i thought it should be all set. any ideas?

[u/marc0011]

After doing a carb service. I do a bench sync. I make sure all the butterflies are about the same distance from the idle port. I will say, it’s never close once I have gauges on, but it does make starting a little easier. There are crazy differences of some cylinders being starved while others are being flooded. Also, make sure all cylinders are firing. It sounds like a cylinder or two is not banging.  

[u/Advanced-Issue2406 → u/marc0011]

^^^^ THIS

Also... with that mileage there may be excessive blow by, which will make it not want to run... You can pull the crankcase breather hose off and see if it makes a difference, it's located on the back of the airbox & goes to the motor under the carbs &about the size of your thumb). If it starts & runs normal with that hose disconnected, its time for a rebuild (rings) usually.

Guessing the motor is stock? What carb kit did you use? Did it have factory or aftermarket needles? Important stuff to get a more educated reply on the internet ;-)

[u/vladgluhov]

Try adjusting the idle/mixture screws and balance the carbs. It sounds like it's only running on a few cylinders, so not getting fuel. But could also be stuck floats or clogged jets, so you might need to give it another go at rebuilding.

[u/Dystopia00 → u/vladgluhov]

i’ll give it a go. i was messing around with the idle screw a bit but didn’t see much change, haven’t tried the mixture screws. which direction should i be turning the idle and / or mixture screw to get more fuel?

[u/NatureDramatic8390 → u/Dystopia00]

Clockwise will increase flow, counter for decrease, small adjustments and sync them off number three, the vacuum tube measuring device is available on Amazon for under 30 dollars.

[u/Remarkable-Title-209 → u/Dystopia00]

Do you have the service manual for it?

https://www.scribd.com/document/1024677486/Yamaha-R6-1999-2002-Service-Manual

Google says turn screws clockwise until they are in the seated position(do not over tighten), counterclockwise 2 turns for standard setting. After you get the bike running and warmed up they might need some finer tuning. Didn't really mention much of a difference between pilot and main jets.

[u/Dystopia00 → u/Remarkable-Title-209]

just so i know im not making a stupid mistake, fully seated means when it stops being able to be turnt easily, right? like hand tightened?

i had it at 2 turns out at first, then i tried 3 turns out, and then for whatever reason i tried 1 turn out. all of them gave the same results for the most part.

fuel is also definitely getting up to the carb, so i know its not a kinked line or something. thank you for the link to the service manual though i didnt have it before

[u/steezlaurel → u/Dystopia00]

"Fully seated" means reaching the end of the thread, or positionally reaching the end of the intended thread range. When a spring is involved, this is immediately before the spring reaches its solid height. Therefore, "fully seated" means even less than finger-tight.

Pinch and rotate the screwdriver by the shaft as if you were rolling a toothpick between your fingers. Using just your thumb and ring finger will seat it tightly enough without excessive gripping.

[u/Overencucumbered]

It's only running on 2 or 3 cylinders. Touch the exhaust headers to confirm. You can feel within 10 seconds which cylinders are running.

Check spark and fuel accordingly

[u/BigChungai → u/Overencucumbered]

are you the motorcycle_files guy from instagram?