Weird carb issue on 81 XS650

[Jake2345]

Hey guys, I'm having a issue with my bike.
So firstly, I decided over the winter to send my bike to a guy I've been dealing with for awhile now to fix my bike, new seals, rejet the carbs, new cam chain etc...
Anyways I've been having a carb issue, the right carb is running a higher mixture, but the right cylinder is struggling to fire, and the left carb is running a lower mixture and the left cylinder is running at a fairly normal rate. I also find that when I let the clutch out and give it throttle it has like a surge or something...it's very hard to explain.
I've got my valves in check and my timing, the spark plugs were just changed not even a week ago. I also pulled the carbs off and re cleaned them just too make sure.
Any ideas on what it might be?
Cheers!

 

[figure8]

Are you sure the right and left carb are in sync? Also both floats are set correctly? Are you running stock ignition?

 

[Jake2345]

I'm using stock ignition. I do have an aftermarket coil sitting at a friends place waiting to be put on the bike.
The floats were set too 27mm we went back down to stock height of 22mm...Bike didn't like either of those so we might try something in the middle.
They were in sync last time I checked but o can always have a shop take a look...but would that cause a very low idle and a surge when I give it throttle?

 

[figure8]

Do you have brass or plastic floats? Brass should be 27 +/-1, plastic is 22 +/-1. I struggled with my 81 carbs when the floats were set incorrectly.
It sounds like your getting inconsistently fuel flow with this surge your talking about.

 

[Kenny Roberts]

Had a problem with carbs earlier this year
O ring around seat for needle was leaking. Caused similar issue until the oring finally gave it up and was leaking way too much fuel
Replaced the ring been like new since

 

[Jake2345]

I have plastic floats. We had to reset them because they were set even higher than they should have been.
I'm going to be rechecking it on Sunday so it gives me time to get some sort of an idea on what it could be.
Kenny; the carbs have been rebuilt, new o-ring for the seat and new gaskets

 

[XSLeo]

Have you read the carb guide? It explains the tear down, cleaning inspecting and adjustment procedures for our carbs.
There are several places that are hard to get clean. Pilot jet passages to the mix screw and on to the holes by the throttle plates. Also the enricher jet in the float bowl. If either of these places have issues then it will be hard to start and not run well.
Leo
Oh, www.amckayltd.com/carbguide.pdf will get you to the carb guide.
Leo

 

[Jake2345]

Thanks Leo! When my friends dad and I are taking the carbs apart we will review that!

 

[Jake2345]

I should add this in there, if I throttle up, and let go of the the throttle, the RPM seems to hold at whatever it's at and then slowly start to come down.
Also had a real hard time coming home from work today, bike actually stalled out and wouldn't start, and when I finally got it started I revved it up and the one side back fired big time with a flame...I turned down the top mixture screw for that side and now the bike has a hard time idling...I'm at a loss

 

[scabber]

The hanging throttle condition is often cured with a larger pilot jet. A 45 worked for me.

 

[Brassneck]

Your carb issues sound like they need to be cleaned (again?) and really inspected...could be a combination of things going on: could be out of sync, and/or too lean, and/or dirty or clogged jets, float height issues..etc. Does the choke affect anything?

Definitely go through the carb guide posted...lots of things to check.

Good luck.

 

[Jake2345]

A lot 25% choke makes it idle just above 1500RPM last time I checked, full choke it sits at about 2200RPM.
I know for a fact that before the bike would idle at about 1200RPM which is what I prefer.

 

[nj1639]

I should add that I turned down the top mixture screw for that side and now the bike has a hard time idling...I'm at a loss

If you're talking about the screw between the top of the carb and the intake manifold then you're leaning out the idle circuit by turning it down.

I've been chasing a hanging idle situation on a couple of my 34's and trying to eliminate if it's carb or electronic in nature.....fun times!

I'd suggest getting those carbs back to a base setting. Take them off, get two straight pins and set them under the throttle plates. The throttle plates will grip the pins equally if they're in synch. If either pin is loose then adjust the screw setting between the carbs which adjusts the right carb throttle plate.......adjust in or out until the pins are gripped the same. Easy peasy.

On the settings between the carb top and the intake- turn the screw in until it bottoms and then turn it out a full three turns. Both sides. Be careful turning the screw in as you just want it to seat. You can place a finger into the carb opening to feel when the needle is starting to seat.....look for the tiny hole which will be below the setting screw. Once it seats then back it out and count the turns.....three turns out, both sides.

Double check your float height. 22mm as stated.

That should get you to a runnable base setting where the only carb adjustment to make at this time may be the left carbs idle set screw to increase or decrease idle of both carbs now that they're synched.

 

[Jake2345]

OK , repulled my carbs off, checked them over and adjusted the floats and the needles. The gentleman who worked on my bike previously said I needed 137.5 main jets. They are in.
My friends dad took it for a test ride, still acting up. Took the old coil off, and put a new one on there still acting up, you could even pull the spark plug wire off on the left side and the bike would still run on.
Anyways long story short the bike is not right, it will have intermittent spark....which leads me too ask, could my tci be going?

 

[nj1639]

TCI could be suspect. It's a great thing to have known working spares of some items so's to be able to swap for testing.

On this hanging idle that I've been chasing I've swapped charging rotors, swapped carbs, replaced the manifold barbs vacuum link (I link the barbs with about a foot of vacuum hose) rechecked bench synch and pilot settings, checked carb boots and manifold gaskets- all to no avail. This is on my '78SE that I've converted over to a TCI setup, otherwise stock. Well, Mr. gooberhead put the TCI black box under the seat for convenience, which they're mounted under the battery box-location determined by the Yamaha engineers- probably for cooling purposes So I relocated it from under the seat to the side of the battery box behind the pod filters AND put some gasket sealant on the intake manifold gaskets.....took her for a ten mile run.
No hanging idle. TCI or gasket seal?
Carbs ran like crap. Pulled, cleaned and checked float levels. Levels were off. Reset, remount and we're good to go. I'm liking these 38's.

 

[Jake2345]

So I'm still having issues with my carbs. Idle is all over the place, never stays settled, balance is good, now I'm not sure what I have for a pilot jet, but for a main I have 137.5, and I think fuel is getting through those main jets and then boom I have my too rich issue.
Anybody else ever had this sort of problem?