Major carb problems

[clarkf]

Hello,
Hope someone can help.
I have a 1989 600 with 1990 carbs. I bought the bike about 2 month ago. It has a full V&H supersport system when I bought it. I installed factory pro advancer, new plugs, air filter. The bike was running very lean when I bought it so decided to rejet. I just recently about 2 weeks ago rejetted the carbs. Now I have rejetted like 6 different motorcycle carbs so far in my life with no problems, so this wasnt my fisrt time. Anyways, cleaned carbs, I went up to 115 mains, 37.5 pilots and 2.5 turns out on mix screws. Changed O rings. Did a visual sync. As soon as I put it back together and fired it up it was screaming at like 6k. Went to 3 turns on mix screw, no change, then 4 turns, no change. So I thought maybe I forgot something, tore it all down, tried again same thing. Tore it all down like 10 times, same result. I decided to change out the Intake O rings, no change. Used black silicone around airbox boots to guarnatee there wasnt a leak there. Decided to put everything back to stock jets, origional air cleaner, no change. tonight I will be tearing them down again, cant even tell you how many times this is. When I put my hand over air cleaner, idle drops, so its sucking air from somewhere. At this point I have no idea where. Any suggestions. Thanks in advance.

[DClark]

If you are thinking air leak, maybe check out the air box. I have a kat 1100 and have no idea what the box is like on your bike but on my bike, the box is two halves that are glued together- you can see the seam on the top where they meet. I sprayed carb cleaner on it and I actually saw cleaner bubble as it was sucked into the joint, freaking out the idle. It was especially bad near the engine blow back entrance. Check it out on your bike. I mixed two new tubes of JB Cold weld, smear that stuff all over that seam and it fixed it.

[Thirdorb]

Wow...it looks like you were very thorough, but did you check your float heights? Especially after a rejet you wanna make sure your floats are at a primo level...

[clarkf]

I checked the airbox atleast 20 times, seriously, Im losing my mind with this bike. I even used black silicone on the boots. Yes I saw the seem and inspected it. I alos replaced the drain cap that goes on the bottom.

The floats I checked when I first open the carbs up, they were at around 16mm, all four. I set to 15mm. First go around, no change, then to 14mm, no change, 13mm and so on. Still no difference.

[DHolzwarth]

Hanging at 6K? I would look to see if the throttle cable is hanging, or if the linkage is somehow jammed or assembled wrong.

Or if the idle screw is way too far in/caught on something. I know it seems obvious, but you haven't mentioned checking either, and it does seem you have been very thorough on the carbs themselves.

Just a thought.

[clarkf]

i did check throttle cable every time I put back togehter. I made sure that butterflies were totally closed, when I connectedd throttle cable and I took idle adjustment all the was down where it was not touching. I did not however take out the A/F screws to make sure something wasnt hanging up. I will try that now.

Thanks

[Wild-Bill]

1. Keep in mind that these AF screws screw in to lean the mix and out to richen it.
2. You changed the mains but didn't lower the needles? Maybe the needles aren't closing off the mains all the way? Try sticking with the 37.5 pilots and going back to the stock mains. If it's still not right try closing down a bit on the pilots by turning the AF screws clockwise.
3. Disconnect the choke cable and make sure the choke plungers are all in.

[clarkf]

I took apart each A/F screw. Everything was there and in the correct spot. Needle, brass washer, oring were all there. O rings looked good.

1. Keep in mind that these AF screws screw in to lean the mix and out to richen it.
2. You changed the mains but didn't lower the needles? Maybe the needles aren't closing off the mains all the way? Try sticking with the 37.5 pilots and going back to the stock mains. If it's still not right try closing down a bit on the pilots by turning the AF screws clockwise.
3. Disconnect the choke cable and make sure the choke plungers are all in.

I origioanlly shimmed the needles with a #4 washer. I then went back to stck thinking maybe the washer was hanging up the slide. Stock needles didnt fix it.
I will try what you said, I will go with th 37.5 pilots and 112.5 mains which were stock. The choke plungers are all in.

[clarkf]

1. Keep in mind that these AF screws screw in to lean the mix and out to richen it.
2. You changed the mains but didn't lower the needles? Maybe the needles aren't closing off the mains all the way? Try sticking with the 37.5 pilots and going back to the stock mains. If it's still not right try closing down a bit on the pilots by turning the AF screws clockwise.
3. Disconnect the choke cable and make sure the choke plungers are all in.

Checked all of this again and same result.

[steves]

What jets did you use?

Sounds like a vacuum leak.

[clarkf]

What jets did you use?

Sounds like a vacuum leak.

Do you mean size or brand? I started with 37.5 pilots and 115 mains. Tried many differnt combos all with no change. I am currently back at stock which is 32.5 and 112.5 with stock needles. Still the same.

As far as brand I used Mikuni jets, same as what came out

[akarob]

Running a .020 wire through the tiny holes in your emulsion tubes may be the answer. It solved my carb issues of hanging idle and such.

The thing is, the holes may look clean and open but they're really not - even if you can see light and spray cleaner through them, it's not good enough.

[clarkf]

Update

I tore everything apart again, checked everything yet once again. Again nothing appeared broken, wrong, out of place etc. Put it all back together and the bike actually runs considerably better. I have the stock mains in with 37.5 pilots and stock needles. It is still lean especially in the midrange, but the 6k hanging idles is gone. The wierd part is I did nothing different this time. Same jets that I tried the past 10 times, same AF settings etc. No Clue what was wrong. I may raise the needles to richen up the midrange and call it a day, considering im totally fed up with these carbs already. Thanks for everybodys input

[Wild-Bill]

In that case it has to have been vacuum leaks. Are you installing the breather box to the carbs before or after putting the carbs on the bike? Recommendation is to do it before to make sure you've got good seals all around. Seems to work well for me.

[clarkf]

I put the airbox on the carbs before putting them back on motor eveytime. I was taking out aircleaner and putting my hand in airbox to push down on airbox boots and then clamping each boot down. This is very wierd becuase like I said I have done nothing different this time, except to tear them apart again and rechek everything.