Troubleshoot CV Carbs

I got a 1989 Suzuki GSX750F Katana last November as part of a trade. I got it running, painted the tank and the fairings, etc, but the carbs are making the engine stumble at 1/4 throttle. It idles fine and past 1/4 is ok, but there us a dead spot in the throttle range. I am trying not to take the carbs apart as working on the induction system on this bike is a royal pain.

FYI: This is my first bike with CV carbs so I don't know what is normal.

Try raising the needles. Since it idles well and runs under power ok, its probably not clogged or dirty jets. Also have you checked the spark plugs? Katanas tend to unloved and neglected, so I wouldn't be surprised if it still had factory plugs, or wrong plugs. Also check for clogged or kinked vent lines and vacuum leaks where the carbs mount to the head.

If none of that helps you will probably need to pull the carbs for cleaning and inspection. If you end up going that route, you should install a "stage 1" style jet kit while you are in there. The factory jetting was seldom ideal.

There is nothing particularly special about CV carbs, the slides raise and lower by venturi effect. The butterflies control the air flow, and thus the slides follow the butterflies. The slide diaphragms occasionally fail, but its not a common failure.

That helped. When it is warmed up it runs pretty well. Kids I got it from abused it pretty well, but it has good compression and no smoke whatsoever.

Did the PO hack out the air box? CV's can be a royal pain with no air box.

Nope, air box is intact. Running much, much better since I tightened teh carb connection. Feels like the carbs might be a bit out of synch, but not bad at all now. It has a very minor delay in initial throttle response, but once the throttle is cracked, it responds well throughout the rest of the range. This is the first "modern" sport bike I have ridden and I must say that I am impressed with the power.

Now I have to get a new set of tires. I am looking for something decent, but which will not break the bank. My favored tire supplier, Tires Unlimited, as apparently bit the dust, so I am in the market for a new supplier as well.

Bike Bandit saves you 10% if your an AMA member but motorcyce superstore had good prices too however check your local guys too a most supply houses have deals right now so they might save you some too.

The only local guys I have are dealers who charge an arm and a leg.