are air/mixture screws horsepower screws? :)

[BobCarter]

I've got an 06 600 and am starting to get the itch for more power. I think I've decided on the yoshi exhaust...nothing loud, which I like...and an ignition advancer.

My question? I keep reading about adjusting the screws 1/4 or 1/2 turn out to richen the carbs. Is this something that will only benefit with doing a jet kit...or can I simply turn the screws a little bit and expect a little more power?

I run an automotive garage and am new to the two wheel scene. If its got 4 tires and fuel injection I can help you though. Thanks for understanding my ignorance.

[squiggy]

Is this something that will only benefit with doing a jet kit...

For just a slip-on the consensus is you don't need to rejet. Just adjust the A/F screws to richen the mixture. Even though a jet kit will give you better throttle response.

...or can I simply turn the screws a little bit and expect a little more power?

No.

It doesn't change compression. It doesn't change timing. If you keep turning those screws, you'll get less power because now the engine is over-rich. It will foul the plugs and be a worse running engine.


If you want more HP get a K&N air filter...woooooooooo. That was a joke.

[Tmod]

I think Cyberpoet wrapped it up the best when he said that the bikes already ran lean from the factory for emissions purposes and now with today's fuels. it is even worse as there is more alcohol then there was before. It will do nothing but good to get a jet kit in combination with the slip-on and while you are at it throw a advancer on there.

Tmod

[The CyberPoet]

First, thanks to TMod for saving me some typing.

I've got an 06 600 and am starting to get the itch for more power.

Dremel out the header weld seams: CyberPoet's "How to grind out your sloppy exhaust header weld seams on a Suzuki"

Install the Ivan's JetKit to fatten up the midrange torque -- how to Install a JetKit in a 98-06 Suzuki Katana (webpage on CyberPoet's site).

Install the FactoryPro Ignition Advancer (CP's offerings - $49 + shipping) to move the torque curve down the RPM range a bit, add more torque to the 4k - 8k range.

Move to a great, light-weight PAO-based motor oil that's rated JASO-MA or JASO-MA2, like Mobil 1 MX 4T or Castrol R4 10w50.

Now tell me you don't love the changes.

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[BobCarter]

Thanks for the help. I am just about at 4k, so I just changed the oil to mx4t and changed all the brake fluid. I am saving right now for a yoshi slip on and the advancer. I'll have to wait a while on the jet kit. Again, thanks for the help

[The CyberPoet]

Thanks for the help. I am just about at 4k, so I just changed the oil to mx4t and changed all the brake fluid. I am saving right now for a yoshi slip on and the advancer. I'll have to wait a while on the jet kit. Again, thanks for the help

Get the jetkit before the exhaust -- the exhaust is a pretty tone, the jetkit is power.

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[suzukiray]

You will gain a better running engine if the screws are out of CORRECT adjustment. The really cool thing about the mixture screws is that the engine will "TELL" you where it wants them to be set! With the bike warmed up & idling, you slowly turn the mixture screw in or out till the motor idles the fastest on that carb, then you move on to the next carb until you've done all 4. If the idle picks up quite a bit turn it back down to normal before continuing to the next carb. Once finished, if done correctly, the bike should idle better, throttle up better & use next to no choke to start unless it is fairly cold outside. Good luck, it is easy to do & a GOOD thing to do to your bike. Ray.

[BobCarter]

how are you adjusting the airmix screws with the carbs installed?

[brooder]

how are you adjusting the airmix screws with the carbs installed?

90* screwdriver

[ctandc]

If you have any experience tuning EFI cars, it's the same reasoning. On a closed loop EFI system, O2 sensors in the exhaust stream, take a reading of the exhaust gas, and tell the computer to richen (more gas less air) the mixture or lean (less gas more air) the mixture out based on these readings.

With an open loop carbed system (no computer controlling mixtures, and no O2 sensors) such as our Katanas, the mixture is controlled by the A/F screws in each of the (4) carbs.

From the factory the carbs are set to a certain mixture. Just like every carbureted vehicle every produced after 1974, this mixture is set lean on purpose (for EPA and smog standards). That doesn't mean it's set at it's most efficient air / fuel ratio, just the best one to get it by EPA mandated testings and standards.

Read this for a decent explanation of the Air / Fuel Ratio

http://en.wikipedia.org/wiki/Air-fuel_ratio

Now...when you adjust the A/F screws in our bikes, you are either making it richer (more gas) or leaner (less gas).

In all actuality, the best power is usually on the lean side. Problem is that too lean can cause engine damage. Too rich will kill power, and gas mileage.

All this is influenced by the intake path (your air filter, air box, etc)..it's also influenced by your elevation (above sea level at a certain point makes the air 'thinner' with means you will need MORE fuel to compensate)...

When you change to a more free-flowing exhaust, you are affecting the mixture as well. You are exhausting the spent gases from the engine more efficiently, so you can actually change your mixture to put more in...

Keep in mind that the internal combustion engine is pretty much just a big air pump.

And contrary to popular belief, the ONLY real way to jet / tune for best power is on a dyno or on a dragstrip. Problem with a dragstrip is that time of day / traction / and drive ability become big variables, especially on motorcylces. On a dyno, it's right there in black and white....not to mention that unless you are racing an engine, you should tune that engine to run it's best in the RPM range you will be in frequently..


Clear as mud?


HTH

[The CyberPoet]

With an open loop carbed system (no computer controlling mixtures, and no O2 sensors) such as our Katanas, the mixture is controlled by the A/F screws in each of the (4) carbs.

Note that these A/F screws (aka Pilot Screws) only control idle and slightly off-idle behavior. There are other settings that control the majority of the fueling above about 1800 - 2000 RPM.

In all actuality, the best power is usually on the lean side. Problem is that too lean can cause engine damage. Too rich will kill power, and gas mileage.

There are normally two fuel-air targets used in the industry:

Complete (Maximum) burn - as complete a burn as possible, where all the fuel is perfectly matched to the amount of oxygen in the air of the mixture, so that at the end of the detonation cycle, both oxygen & fuel are totally consumed. The EPA generally desires this, and wants manufacturers to have their bikes (& cars) run perfectly at this setting or very close to it. The problem is that the setting has to change as the fuel changes formulation (alcohol contains oxygen bound up in it, and doesn't have the same oxygen-consumption rates as standard gasoline, so running ethanol requires a slightly richer mixture to accomplish this same "complete burn" without going too lean -- see Wiki entry - more info on fuel vs. Stoichiometric ratios). This is most evident at idle, where the engine is consuming the least amount of fuel and has the least amount of rotational momentum to carry it's moving parts to the next detonation.
Generally, maximum burn nets you the best miles-per-gallon, because no spare fuel is being wasted in the process. This setting also tends to give you the best top-end speed, because at maximum RPM's, it is maximizing the fuel use.

Maximum torque - this is against EPA guidelines, is a somewhat richer mixture, and leaves some unburned fuel exiting into the exhaust, but increases the torque output of the engine and the vacuum-building characteristics. This is generally what the various aftermarket stage 1 jetkits target as the ideal they are trying to hit, and why they perform differently than the OEM jetting.

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[suzukiray]

VERY nice writeup Cyber! Ray.

[The CyberPoet]

VERY nice writeup Cyber! Ray.

Thanks -- which one?

Cheers,
=-= The CyberPoet

__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.

[suzukiray]

Did you get my PM about the parts I am in need of? Thanks, Ray.

[ctandc]

Note that these A/F screws (aka Pilot Screws) only control idle and slightly off-idle behavior. There are other settings that control the majority of the fueling above about 1800 - 2000 RPM.

I understand that, was just trying to give him a quick and dirty breakdown...

There are normally two fuel-air targets used in the industry:

Complete (Maximum) burn - as complete a burn as possible, where all the fuel is perfectly matched to the amount of oxygen in the air of the mixture, so that at the end of the detonation cycle, both oxygen & fuel are totally consumed. The EPA generally desires this, and wants manufacturers to have their bikes (& cars) run perfectly at this setting or very close to it. The problem is that the setting has to change as the fuel changes formulation (alcohol contains oxygen bound up in it, and doesn't have the same oxygen-consumption rates as standard gasoline, so running ethanol requires a slightly richer mixture to accomplish this same "complete burn" without going too lean -- see Wiki entry - more info on fuel vs. Stoichiometric ratios). This is most evident at idle, where the engine is consuming the least amount of fuel and has the least amount of rotational momentum to carry it's moving parts to the next detonation.
Generally, maximum burn nets you the best miles-per-gallon, because no spare fuel is being wasted in the process. This setting also tends to give you the best top-end speed, because at maximum RPM's, it is maximizing the fuel use.

Maximum torque - this is against EPA guidelines, is a somewhat richer mixture, and leaves some unburned fuel exiting into the exhaust, but increases the torque output of the engine and the vacuum-building characteristics. This is generally what the various aftermarket stage 1 jetkits target as the ideal they are trying to hit, and why they perform differently than the OEM jetting.

Cheers,
=-= The CyberPoet

Yes you are correct.

EPA wants a LEAN mixture (less unburnt fuel out of the tailpipe) Same reason they introduced EGR systems...to put the exhaust gas back into the combustion chambers to get as much of the unburnt fuel burnt as possible.

Maximum torque is the same as truly tuning an engine for the street (whether it's a car or a motorcycle) tuning it for the RPM's it will see alot of....

And contrary to that, the highest HP readings are usually gained from a leaner mixture that lessens off-idle and midrange torque...

Just like the difference between quick and fast..



__________________________________________________ ________
CyberPoet's Katana Maintence and Upgrade Parts Offerings
The Best Metal Steel Aluminum Motorcycle Tire Valves in the World, plus lots of motorcycle & Katana (GSX600F / GSX750F) specific help files.[/quote]