Need help from Carb gods!!!

[Daemontrym]

Everyone has seen me post about my endless saga with my 93 Kat 600. Ok I have now sealed the airbox, cleaned the carbs, returned them to stock jetting, checked the floats, synced them, replaced the spark plugs, bought a new stock style air filter, and set them according to arsenic's/ manual's recommendations.

My issue is a bad flat spot that wont go away between 3,500-7,000 RPM. Its like a huge bog then just wants to become a bucking bronco through the rest of the rev range.

Would these symptoms fit the bill for worn out emulsion tubes?

[Wild-Bill]

I haven't been following your issues too carefully so I'm not completely sure where your bike stands. Emulsion tubes are a possibility but so are clogged/insufficiently cleaned pilot circuits, improperly set A/F screws (you want 2.5 turns out) and non-synced carbs. The bucking would make me think emulsion tubes or sync. If you've already vacuum synced and the bike idles well then try pulling the tubes out, stand them up on a scanner and then use Powerpoint or MS Paint to superimpose a circle on the image. That'll show you really well if the tubes have taken on a non-round shape.

If the tubes aren't round then you may have found the trouble. If you're replacing them then you might want to think about installing a FP jet kit. The altered contour on the needles will help that mid-range a bunch.

[Kreylyn]

Emulsion tubes could cause an issue in that rpm range. My experiance was they made it impossible to keep a constant speed in that rpm range, but acceleration was not an issue really.

That large and strong of a hesitation as you describe really leads me to think more of a fuel level issue. Are you absolutely sure you have the correct float levels and they are freely moving so as not to "stick" in the closed position? Also, are you sure you have fuel flowing freely from the fuel tank? No inline filters that could slow things down, or line kinks for example.

Krey

[Daemontrym]

ill let you know because im borrowing a caliper from my dad once he gets off of work. plus I will check the emulsion tubes.

[arsenic]

When you check the emulsion tubes, make sure you take them all the way out. Take the main jet off the bottom. Just hold the needle jet (emulsion tube) and make sure it's round. If you do it the lazy way and just look down the carb throat with the needle out, it's gonna look weird.

[Daemontrym]

The emulsion tubes I think are fine, when I took them out they looked round and didn't have any ovaled spots.

I had to bring the floats up 1.5MM so they would be in the stock position.

The bike idles a bit better but still has the bad bog in the 4-7k range. I sprayed some starting fluid around the carb boots and the bike didn't try to rev up.

I decided to cover some of the open plastic hole in the airbox with my hand and the bike would quickly rev up, the more I covered the higher it would rev.


My father and I have brought many old bikes from their grave, but we have never seen anything like this!

[Wild-Bill]

Partially covering the air intake effectively richens the mixture. With that, If the A/F screws and floats are right, the emulsion tubes/needles are good, you've got the stock filter and the airbox drain is capped off then chances are you haven't got the pilot circuits completely cleaned, the vacuum hose going to the petcock is cracked or you're missing the o-rings at the tops of the carbs.