gen3 carb jetting with mods.

got my gen 3 carbs out and its time to tune it up.. my bike has a k&n and a slip on exhaust for mods.. my question is, what is the best jetting setup for this bike at sea lvl.

 

Make it richer is a good rule of thumb. Fuel screws 3 turns out from fully seated, up 1 size on the pilot jet, shim up the needle, and 1 larger on main. Dyno's are awesome especially if they have the exhaust gas sniffer.

 

Like tinkerinWstuff said, all bikes are a little different. I have a 93 and I also have a K&N air filter with a (yoshi) slip-on. I've tried the stock 130 jets and found that I had backfire on startup and I was running really rich. So I went with 125s and 128s and found it to work out pretty good. You kind of have to play around with it to see what is right for the bike. It can be a pain in the ass. Dyno would still be the best way to go though.

 

Whatever you do don't drill your slides: http://vfrworld.com/forums/mechanic...-slides-avoid-buying-jet-kits-drill-bits.html

The greatest things that i've seen jet kits do, are increase fuel consumption, plug fouling, and sluggish throttle response, plus extra dirty exhaust tips.

You could just adjust your mixture screws if you need more fuel at idle and transition. i would advise not go up one pilot size and also open the mixture screws--guaranteed too much fuel and your mileage will go down to the low thirties or lower, and it won't make an extra horsepower.

If you really need more fuel at WOT, then just change the main jet and leave the needle and slides alone. But like the submariner said, he had to go to a smaller main jet. Why? Because if you really are flowing more air then the carburetor is already designed to meter out the corresponding fuel for that extra air. More air flow causes the needle to rise higher and expose a narrower diameter due to the taper, but if you are running at a higher volumetric efficiency then you won't need as much more fuel for that air as the stock main jet supplies. Hence the smaller mains making more power. It's not so counter-intuitive once you think on it some.

For the mods that you listed, i would have to respectfully disagree with all of the recommendations from pjvtec. Extra fuel is just wasted and makes no extra power. The KN filters are more restrictive and flow LESS air than the stock air filter--there is some dyno data out there that proves it. The open cans sound good but don't really increase power or torque. Camshaft modifications are the only way to significantly increase airflow, and the secret to power is air, not fuel. If you can get the extra air, then fuel can be added to make more power. Just throwing more fuel at it does nothing.

Unless you race or do mostly twisties, you are probably at 1/4 throttle or less for 80% of your riding--which is all coming from the pilot and transition circuits.

Gas analyzer tuning is the way to go if you can find someone skilled in the art. Real live action data beats BS any day of the week.

Want to do a quick test to see if more fuel is better or worse? Just open your choke lever while at WOT and see if it helps or hurts your power. Give us a report back on the results.

What the hell Tink, i've always been fond of them dirty girls--especially ones that likes to go out behind the bar and do a little dumpster divin'.