Carb troubleshooting help needed

[DavePlum]

These are 82 XJ carbs going on my 80SG project. I purchased the carbs off of craigslist and cleaned them and made sure all passages were clean and clear. I'm having trouble with carb #4 (fuel dripping out of throat on air box side)
I'm trying to pinpoint the problem but no having any luck. Here's what I've done trying to determine the problem:
First I swapped out the #3 & #4 float valve, put fuel to carbs and leak is still there on #4.
Next I swapped out the #3 & #4 float needle seat, fuel to carbs, same same
Next I swapped out the #3 & #4 float, fuel to carbs, tapped on fuel bowl with screwdriver handle ...same same
I know the floats are good as I did a good visual inspection and even checked them for any small leaks.
My understanding is this problem can occur when any one of these happen:

1 Bad float (not buoyant enough to raise the needle onto the seat)
2 Needle valve worn to the point it won't seat
3 Valve seat dirty not allowing needle to properly seat causing fuel leakage
4 Float is hanging up

What am I missing here? Because swapping everything from #3 to #4 didn't make #3 leak I'm leaning towards the float itself hanging up and not raising enough to stop the flow of fuel but I can't see why it would be doing that. The bowl gaskets are new and yes, I even tried swapping out the bowl gasket (despite they were exactly the same) only to get the same results. I also swapped out the fuel bowls!

Any ideas or suggestions?

[Padre4art]

Mine were leaking because the floats were topping out on the carb body before the needle was fully depressed into the seat. If the carbs are on your bench upside down, and you press down lightly on the float and it clunks into the carb body you may have this issue and need to adjust float level.

Hope it helps!

Art
79F, 730 miles

[motoman]

O-ring on needle seat possibly leaking, no matter being swapped.
Using a Q-tip and a dab of metal polish, polish ALL the float seats.
Switching float needles and seats around, float settings NEED to be checked and corrected(23mm). Then leaving bowls off, flip carb bank upside down and let set fairly level. With a fuel supply above carbs, hook up both fuel lines and watch for any leak around float needles. Leave that way for approx. an hour.
If no leak, report that back and we'll go from there.

As suggested, make sure all eight floats are hanging perfectly perpendicular, or you can have a float hang against side of bowl and not see it with bowl on carb. Also check that all floats are hanging the same distance down. If that #3 float hangs lower than the other three, there is another tab you bend a tad to get it the same as ones that are not an issue.

[DavePlum]

Thanks Art, I've already adjusted the float levels to what's specified for the 78-80 carbs. I understand the 82 carbs are adjusted differently (using the clear tube connected to bowl drain method) but I was hoping I could get it close enough to see if the bike would fire up. I'll check the floats tomorrow and see if I'm having the problem you described. It's odd it's only #4 carb I'm having this issue with but nothing been easy with this bike...lol. Thanks, Dave

[DavePlum]

Motoman- these are 82XJ carbs, I was under the impression the float levels are determined via the clear tubing attached to fuel bowl drain method? I'll polish the seats and use the method you described, we'll see what happens...thanks

[TopCatGr58]

Thanks Art, I've already adjusted the float levels to what's specified for the 78-80 carbs. I understand the 82 carbs are adjusted differently (using the clear tube connected to bowl drain method) but I was hoping I could get it close enough to see if the bike would fire up. snipThanks, Dave

Hey Dave,

The float height specs for the 78 carbs is too low at 25.7mm, the 80-81's used ~23.00 mm's and then the clear tube method.

Secondly, you said you cleaned them, but didn't specify what parts are in it, GENUINE Mikuni float seats/needles, or generic K&L brand? It's been shown that the generic ones don't fit as well, and the little spring plunger rod isn't as long, as well as the needle itself isn't as long, so the float tang isn't able to push against the needle as effectively. I can't remember who posted the comparison with photos, but it was obvious once you saw them side by side. SO....you may need to acquire the Geniune Mikuni parts before it will behave properly.

T.C.

[motoman]

Motoman- these are 82XJ carbs, I was under the impression the float levels are determined via the clear tubing attached to fuel bowl drain method? I'll polish the seats and use the method you described, we'll see what happens...thanks

Fuel bowl fuel levels are to be checked with bike idleing. Reson being is #1: the teeny internal spring of the float needle will compress a little in order to create pressure enough to seat the float needle shutting off fuel. This taking place does not truly allow for correct running level. Running bike at an idle, fuel level is 3mm down from top of bowl casting. In simpler terms, that is middle of lock washer on fuel bowl retaining screw. The '3mm down from top of bowl casting' was also amended in original Yamaha service/ repair manual. True, in order to get all four carbs at identical fuel levels, notations have to be made, remove carb bank, then fuel bowls and adjust floats as necessary.....then repeat installation and running check procedure for hopefully corrected fuel levels.
No worries....I can say I've removed and installed same carb set five or more times in order to achieve correct, identical fuel levels. I can say that getting those running fuel levels precise makes a HUGE difference with engines smoothness crusin' LD out on the Interstate........once idle mixtures and sync are done as the final true-tune.
As a word of advice, 1mm of actual float bowl change equals approx. 3mm of actual fuel level change, so 'tweak' those float bowl/ float needle stops very carefully in order for all four carb fuel levels to be equal!
The good part...........your gonna get really quick at removing and installing a carb bank. FWIW, I have cut that down to under 12min..
BTW, 23mm IS the INITIAL correct static float level setting for 80- 81 XS11's and 82XJ's. Final RUNNING fuel levels are used for 81XS11's-XJ 1100's.

[FJ111200]

Thanks Art, I've already adjusted the float levels to what's specified for the 78-80 carbs. I understand the 82 carbs are adjusted differently (using the clear tube connected to bowl drain method) but I was hoping I could get it close enough to see if the bike would fire up. I'll check the floats tomorrow and see if I'm having the problem you described. It's odd it's only #4 carb I'm having this issue with but nothing been easy with this bike...lol. Thanks, Dave

I had this problem with a set of XJ1100 carbs.
In the end I found out that it was the float hanging up on the aftermarket gasket that I was using. JAT.

[motoman]

I had this problem with a set of XJ1100 carbs.
In the end I found out that it was the float hanging up on the aftermarket gasket that I was using. JAT.

This scenario has also been true. Problem being, when fuel bowl is tightened down, gasket to mating surfaces get squished outward a tad from compression between the two mating surfaces.

[DavePlum]

Okay, I polished up the seat and adjusted the float on #4 carb and it did the trick, no more leak. Installed carb bank, throttle cable, vacuum line and attempted to fire her up for the first time. It's a no go. Engine cranks over but she doesn't even sound like she wants to start. Time to troubleshoot ignition system and already found a problem. Because it was so easy to check I started by checking resistance from pickup coils. Resistance on #1 pickup coil was about 18.2M ohms...should be 720 ohms +/- 20%(measured from 4 pin connector going into TCI) #2 pickup coil measured 801 ohms ...guess I'll go from there, wish me luck.

[motoman]

Okay, I polished up the seat and adjusted the float on #4 carb and it did the trick, no more leak. Installed carb bank, throttle cable, vacuum line and attempted to fire her up for the first time. It's a no go. Engine cranks over but she doesn't even sound like she wants to start. Time to troubleshoot ignition system and already found a problem. Because it was so easy to check I started by checking resistance from pickup coils. Resistance on #1 pickup coil was about 18.2M ohms...should be 720 ohms +/- 20%(measured from 4 pin connector going into TCI) #2 pickup coil measured 801 ohms ...guess I'll go from there, wish me luck.

Good to hear float adjustment and polishing float needle seat resolved #4 carb issue. Your headed correct direction following out secondary ignition for other issue.

[TopCatGr58]

Okay, I polished up the seat and adjusted the float on #4 carb and it did the trick, no more leak. Installed carb bank, throttle cable, vacuum line and attempted to fire her up for the first time. It's a no go. Engine cranks over but she doesn't even sound like she wants to start. Time to troubleshoot ignition system and already found a problem. Because it was so easy to check I started by checking resistance from pickup coils. Resistance on #1 pickup coil was about 18.2M ohms...should be 720 ohms +/- 20%(measured from 4 pin connector going into TCI) #2 pickup coil measured 801 ohms ...guess I'll go from there, wish me luck.

Hey Dave,

If you haven't seen it, follow this link/tech tip for your PickUp Coils/wires!
http://www.xs11.com/forum/showthread.php?t=543

T.C.

[DavePlum]

Actually no, I haven't seen that. I just happen to be searching the forum on this subject so thanks, it will be helpful and I need all the help I can get...lol