Xj550R Doesn't like to run at low RPM

It'll do fine down the highway, it'll start up just fine. It mostly runs fine, but it has some issues.

It likes to die at stop signs, and bogs down in first gear even at high throttle/RPM.

But once I get it back up to speed, it runs fine.

If I turn the choke on a bit just to stop, it'll idle high but it'll run fine, but without the choke on it sputters and dies when it's not moving.

I put 100 miles on it and the plugs look fine, maybe a tad lean.

Valve's were checked, shims are in spec. Carbs have been thoroughly cleaned, and when it runs it seems to run well so I don't think syncing is an issue. I sprayed down all of the rubber to check for a vacuum leak and couldn't find one.

To me it sounds like the pilot jets, but I know how thoroughly they were cleaned so I want to see if anyone more experienced knows what the alternative might be before I pull the carbs again.

It's an 81 xj550r seca. Any help is appreciated.

 

What kind of gas mileage are you getting?
On my XJ650, it is rather finicky about synching. If it ain't right it's not happy.

 

If it bogs no matter what the throttle pull is than i would guess fuel delivery issue

Also, mixture screws set? It was about a half turn difference between running bad and good for me

 

you said pilot jets were cleaned did you make sure the passages were clear too? there is 2 little holes in the front of carb in the throat just above the butterfly s and an air jet under the diafram that must be clear.
mixture settings as stated above.
the enrichment circuit (choke) lets fuel in when starting when you shut it off the pilot jets take over for your idling
your idle speed should be 1200 rpm, could be you just need to adjust that a bit

 

Turned the idle up, took the pilot screws out and made sure they were spotless, set them out a little bit more than they were before and it's running better now.

It still likes to do the same thing though, and I think it's only when it's hot.

EDIT: And I don't know the fuel economy, I've only put around 150 miles on it so far.

 

Are the air jets location correct?

Gary H.

 

by pilot screws do you mean mixture screws? located top front outside carbs.
I am talking about the pilot jets circuit in the bowls. if the passages are not clear you will not get a good idle.
go to this link page 13 through 20 show the pilot fuel circuit and you will see the passages that need to be clean.
http://www.xj4ever.com/inside your carbs.pdf

 

this is from INFORMATION OVERLOAD
would be a good place to read about what is happening with carbs
http://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/

Why your engine seems to be schizoid:

A hanging idle---one that stays high and slowly comes down when decelerating---is a sign of lean mixture. The opposite case, where the idle drops dangerously low then rises, is a sign of rich mixture.

A bike that runs better when hot is probably lean, and a bike that runs better when cold is probably rich.

But sometimes a bike that can be adjusted "just right" when cool, but actually starts exhibiting signs of running lean (hanging idle) as it warms up. And if the idle speed is then re-adjusted while the engine is warm, but eventually falls and the bike dies (especially when sitting at a stop light). Or if the pilot screws are adjusted, then it's too rich when cold---all in direct contradiction of the above observations.

Experience shows that this is a sign of worn throttle shaft seals.....the aluminum carb bodies expand with the heat, but the steel throttle shafts---resting comfortably in a nice cool airflow---don't heat up and therefore don't expand. Once the shaft seals get old and hard, they no longer are able to flex and fill the gap.....so the carb starts drawing air around the shafts, leaning it out.