Sputtering, Bucking, and Backfiring

[sschevydriver]

Hello everybody,
I have a 1999 600f 58,000 miles. I just got the bike for free and don't know any of the history on it. It will only idle with the choke on, and then it idles at about 7000 rpms. The lowest that I can get the idle is about 3000 with the choke half way on. It dies with the choke off, warmed up or not. When riding, it seems to have smooth power only above 8000 rpm, it bucks and surges if I ride below that. I have replaced the needle and seats, and adjusted the floats. All of the jets were clear and the inside of the carbs were clear of any varnish or buildup. I replaced all four spark plugs, and adjusted the valves. Some of the intake valves were tight, but not by much. I have tried running the air screws everywhere from 1/2 turn out, to 3 1/2 turns out. I tried to run it with no air filter, and it would start, but die as soon as I touched the throttle. The weird thing is, that after all of this, it has made absolutly no difference at all. This makes me think that I haven't even touched the problem area yet. It acts the exact same, before and after I tried all of these repairs. The way it stutters and pops, I am convinced that it is an air/fuel problem. The petcock works fine, and the gas is clean. This is a total bummer, I'm really hoping I can get some leads from this forum, it's almost become a personal mission for me to figure this problem out. I like to do all my work myself, so taking it to a shop is not something that I want to do.

Please HELP!!!

[Wild-Bill]

You're right on the money suspecting it's an air/fuel problem. You may have hosed out the jets but what you didn't mention is soaking the carb bodies. The CV carbs on these things are notorious for getting gummed up if you let the bike sit too long. Hit the "Katana Wiki" link at the top of this page and search for "Carbs 102". Read the whole thing, head to Autozone for a gallon of Berryman's Chem Dip and go to town on those carbs. Adjust the A/F screws to 2.5 turns out, bench sync the carbs and you should be running again. As soon as you get the carbs back on the bike and get the engine warmed up do a vacuum sync. That should have her purring no problem.

[sschevydriver]

Hey,
Thanks for the quick response. It is true that when I changed the needle and seats, I didn't give any of the passeges any kind of attention. I've read about people actually soaking the carb bodies completely submersed in Berryman's for 24 hours before trying to clear the passages. I will give that a try, and post my results.

Thanks again.

[DClark]

Get a can of Berryman's aerosal. Remove the idle screw, insert the little red tube in there and blast away.
Next, remove the bowls, make sure they are clean. Find the pilot fuel jet in there, remove and soak, those are probably clogged too.

[05RedKat600]

Get a can of Berryman's aerosal. Remove the idle screw, insert the little red tube in there and blast away.
Next, remove the bowls, make sure they are clean. Find the pilot fuel jet in there, remove and soak, those are probably clogged too.

What will cleaning the idle adjuster do?

[Wild-Bill]

It'll clean the passages leading from there to the carb throat although sschevydriver (who I shouldn't be helping since I like Fords) will get a lot better results from soaking the carbs.

[05RedKat600]

It'll clean the passages leading from there to the carb throat although sschevydriver (who I shouldn't be helping since I like Fords) will get a lot better results from soaking the carbs.

That's the air fuel screw, not the idle screw silly.

[Wild-Bill]

I'd guess (and did) that DClark meant the idle air (air/fuel mixture) screw. He knows that unscrewing the idle adjuster wouldn't give you access to much of anything.

Silly.

[sschevydriver]

So, I removed the carbs again to do the chem-dip soak procedure. When I took them off this time, I noticed that the inside of the carbs were wet. The sliders were wet, and so were the inside of the boots that act as the intake manifold. I'm sure that I this means that I was running really rich, plus I was getting horrible gas mileage while I was riding it the way it was. I'm wondering if the carbs were gummed, then wouldn't I have been running lean? My other thought was that it they carbs were gummed, then maybe the fuel would be making drips, instead of a misty spray. I don't know, they're soaking now so we will see. The other thing that I was worried about was the throttle shaft seals, the shaft that the butterfly valves are screwed to. The Berryman's says that it will kill rubber parts. I have them soaking so the Berryman's only goes half way up the circular opening, keeping the fuel passeges submerged, while keeping the throttle shaft dry. I wanted to sink the whole carb in Berryman's but I didn't want to risk ruining those seals becuase they don't come in the rebuild kits that I have.

[Wild-Bill]

Those seals are made of felt. They'll put up with the soak just fine although you'll need to work some oil in there since the dip will wash the oil out. When the bike's running they get re-lubed with fuel residue. Chances are your carb throats were wet because the float needles were leaking and flooding the carbs.