Question Drilled Air Screw Plug on my '90 GSX600F

[dnelli]

I have a question regarding setting my air screw that I removed from my carbs...

I drilled out my air screw brass plug on all 4 carbs. I wanted to clean that circuit out, since i have the carbs apart. I marked the air screw position with a scribe mark, prior to removal. Then I removed the air screws and they all seemed to be set at about 1/2-5/8 out. KatWiki says:

"1990-1997

600

• Type BST33SS
• Main jets 112.5
• Main air jet 0.5 mm
• Jet needle
  • California 5F105
  • Except California 5F104
  
  
• Needle jet P-2
• Pilot jet 32.5
• Pilot air jet
• California 1.45 mm
• Except California 1.55 mm
• Starter jet 35
• Float height 14.6 +/-1 mm (0.57 +/- 0.04 inch)
• Fuel Screws 1.5 Turns out from stop"

My question is, should I re install them to their original position (1/2 turn out) that I marked or should I adjust them to "Fuel Screws 1.5 Turns out from stop" ?

What is a fuel screw..is it an air screw? This has me a little confused. If and air screw and a fuel screw are synonymous, why is it turned out 3 times more than stock?

Please let me know. The clymer manual says it is "Pre-Set" and doesn't give you a number of turns out.

Thanks

[Kreylyn]

From lightly seated, back them out 2.5 turns.

The OEM settings were lean to meet EPA standards 20+ years ago. Fuel has changed since then, especially when you consider ethanol additives in today's fuel. Thus... why the recommended change in settings.

Out will increase the amount of fuel in the mixture.

Ultimately the best way to tune the carbs is to do a drop down method tune on the Air Fuel screws or... use equipment to measure the setting. 2.5 turns will get you really close to start though.

Krey

[dnelli]

WOW...that seems like a lot compared to what it is stock. I remember other engine air screws at 1.75 turns out. I will set it at 2.5, definitely! When you say, "...to tune the carbs is to do a drop down method tune on the AF screws...". Can you please explain a drop down method tune on the AF screws? Also, what equipment to measure the setting are you referring to? I did get a 4 gauge sync tool. Lastly, how do those motion pro 110 degree long air screw drivers work on a 600 Katana? Are they accessible once the carbs are mounted to the intake boots with this screwdriver or is it a waste of money for my model bike? What about the thumb air screw jets that FP sells, would that make it easier to get to? You use them Kreylyn?

[Kreylyn]

WOW...that seems like a lot compared to what it is stock. I remember other engine air screws at 1.75 turns out. I will set it at 2.5, definitely!

For a US model Kat, it's what works. Euro models are a different story, but then they have completely different jetting.

When you say, "...to tune the carbs is to do a drop down method tune on the AF screws...". Can you please explain a drop down method tune on the AF screws?

Google search for more details, but the simple...

AFTER the bike has been synced and is running/idle properly... use the idle adjuster to lower the RPM as low as they will go and the bike still idle. Probably put it around 800rpm or so. Once it's low as possible...

Paying close attention to how much you turn the a/f screw, adjust carb 1 AF screw in until you hear the idle change. Then back it out until it does the same. You should have 2 numbers now... one for the in, one for the out... where the bike started to stumble. You want to set the a/f screw half way between. So if the bike idle stumbles at 1.5 in and 3.5 out... halfway is 2.5 turns. That would be the specific setting for that cylinder. adjust idle as nessasary to again be as low as possible, and repeat steps on each carb. These adjustments will improve how the bike idles, so you may need to make rpm adjustment each time.

Also, what equipment to measure the setting are you referring to? I did get a 4 gauge sync tool.

Gas Analyzer for the exhaust (also generally used on a dyno machine).

Lastly, how do those motion pro 110 degree long air screw drivers work on a 600 Katana? Are they accessible once the carbs are mounted to the intake boots with this screwdriver or is it a waste of money for my model bike? What about the thumb air screw jets that FP sells, would that make it easier to get to? You use them Kreylyn?

I don't use the long boys, as you would need real small hands to reach the inside ones. Possible, but...

As for the screw driver, it will work... it's not easy. Don't get a cheap one, as that's just asking for frustration.

Either way, it's much easier to do this with both main fairings off the bike for easier access to the carbs.

Krey

[dnelli]

For a US model Kat, it's what works. Euro models are a different story, but then they have completely different jetting.



Google search for more details, but the simple...

AFTER the bike has been synced and is running/idle properly... use the idle adjuster to lower the RPM as low as they will go and the bike still idle. Probably put it around 800rpm or so. Once it's low as possible...

Paying close attention to how much you turn the a/f screw, adjust carb 1 AF screw in until you hear the idle change. Then back it out until it does the same. You should have 2 numbers now... one for the in, one for the out... where the bike started to stumble. You want to set the a/f screw half way between. So if the bike idle stumbles at 1.5 in and 3.5 out... halfway is 2.5 turns. That would be the specific setting for that cylinder. adjust idle as nessasary to again be as low as possible, and repeat steps on each carb. These adjustments will improve how the bike idles, so you may need to make rpm adjustment each time.



Gas Analyzer for the exhaust (also generally used on a dyno machine).



I don't use the long boys, as you would need real small hands to reach the inside ones. Possible, but...

As for the screw driver, it will work... it's not easy. Don't get a cheap one, as that's just asking for frustration.

Either way, it's much easier to do this with both main fairings off the bike for easier access to the carbs.

Krey

Thanks Krey. I did try googling how to do this before i bothered you with a reply. I got the crabs totally cleaned and reassembled last night. I was going to install two inline, brass-sintered fuel filters as the tank has some rust particulate still left inside and there seemed to be rust residue in the bowls. Do you know the clearance between the underside of the tank and the top of the carbs? I am wondering where i want to cut fuel lines to accommodate these filters?

[Kreylyn]

Thanks Krey. I did try googling how to do this before i bothered you with a reply. I got the crabs totally cleaned and reassembled last night. I was going to install two inline, brass-sintered fuel filters as the tank has some rust particulate still left inside and there seemed to be rust residue in the bowls. Do you know the clearance between the underside of the tank and the top of the carbs? I am wondering where i want to cut fuel lines to accommodate these filters?

Don't bother...

IF you have rust in the tank, vibration and sloshing of the fuel will cause particulates so small that no filter is going to work for you. Nothing will filter those out, and they will make it to the carbs. Once in the carbs, they will settle into a sludge in the bottom and eventually block off the pilot jets and other ports.

Simply put... ditch the rust or no matter what else you do the carbs are going to need to be cleaned again... and again... until you do resolve the rust in the tank.

A simple quick fix on tank rust is a gallon of vinegar, soak for 48 hours sloshing it around well every so often. Drain, rinse with water. Drain, rinse with baking soda /water mix... rinse with water. Use a cup of rubbing alcohol sloshed around to get the last little bit of water out of the tank. Blow dryer to dry the tank (alcohol will evaporate fast that way).

Use 1 cup fuel/1 cup oil to coat the inside of the tank after it's clean and dry. This will help prevent future rust some. Best option is Por-15 tank sealer when you can in the future, but those steps will get you going to start.

Krey

[dnelli]

Don't bother...

IF you have rust in the tank, vibration and sloshing of the fuel will cause particulates so small that no filter is going to work for you. Nothing will filter those out, and they will make it to the carbs. Once in the carbs, they will settle into a sludge in the bottom and eventually block off the pilot jets and other ports.

Simply put... ditch the rust or no matter what else you do the carbs are going to need to be cleaned again... and again... until you do resolve the rust in the tank.

A simple quick fix on tank rust is a gallon of vinegar, soak for 48 hours sloshing it around well every so often. Drain, rinse with water. Drain, rinse with baking soda /water mix... rinse with water. Use a cup of rubbing alcohol sloshed around to get the last little bit of water out of the tank. Blow dryer to dry the tank (alcohol will evaporate fast that way).

Use 1 cup fuel/1 cup oil to coat the inside of the tank after it's clean and dry. This will help prevent future rust some. Best option is Por-15 tank sealer when you can in the future, but those steps will get you going to start.

Krey

How does the POR-15 tank sealer work compared to Kreem? I've used the Kreem and wasn't happy with it. I read and followed directions for its use. I am wondering if you ever used both to hear your comparison? Also, would you use the POR-15 tank sealer kit or do the above then pour in the tank sealer?

[Kreylyn]

How does the POR-15 tank sealer work compared to Kreem? I've used the Kreem and wasn't happy with it. I read and followed directions for its use. I am wondering if you ever used both to hear your comparison? Also, would you use the POR-15 tank sealer kit or do the above then pour in the tank sealer?

Kreem is shit... it's basically a latex like coating substance that is only gas resistant on it's surface. If that gets dmged, it dissolves, it does not prevent the rust from continuing on the metal, and with a short time it's going to fail and cause all kinds of craptastic nasty mess issues.

Por-15 bonds to the metal of the tank. It's a permanent bond and seal. It does not allow the rust to continue. I've cleaned kreem out of lots of tanks, and put Por-15 back in... I have it in my current ride now for years, it's great!

The motorcycle kit comes with a pre cleaner that will prep the tank for the sealer. I see no reason it would hurt to pre clean the tank before the prep solution, but that's what it's designed for also. It may simply be superfluous. Depends on how bad the tank is inside.

Krey

[dnelli]

Kreem is shit... it's basically a latex like coating substance that is only gas resistant on it's surface. If that gets dmged, it dissolves, it does not prevent the rust from continuing on the metal, and with a short time it's going to fail and cause all kinds of craptastic nasty mess issues.

Por-15 bonds to the metal of the tank. It's a permanent bond and seal. It does not allow the rust to continue. I've cleaned kreem out of lots of tanks, and put Por-15 back in... I have it in my current ride now for years, it's great!

The motorcycle kit comes with a pre cleaner that will prep the tank for the sealer. I see no reason it would hurt to pre clean the tank before the prep solution, but that's what it's designed for also. It may simply be superfluous. Depends on how bad the tank is inside.

Krey

On the surface my tank looks better than what's on eBay. It did spring a pin hole leak that I had patched and braised that you won't see because it is underneath of the left side fairing. After I emptied the stale fuel, I head a lot of stuff rolling around in the tank. I used a magnetic wand to pull the majority of it out, though I realize it is still oxidizing while it is sitting waiting to be used.

Kreem is shit in my experience too. I used it in my Harley, hence my sketchiness of another type of product. The POR isn't cheap, but if it is good and it works, eff it. I'll do that too. It is just another sub project to the main project of getting this bike resurrected. Thanks!

[dnelli]

one more thing....is a half quart enough to coat the tank, or should I get the bogger kit that comes with the quart of sealer?

[Kreylyn]

one more thing....is a half quart enough to coat the tank, or should I get the bogger kit that comes with the quart of sealer?

The half quart is more than enough. It's a very thin layer is all that's needed. Almost like a paint layer thickness.

Thicker is not better here. Do the normal application (turn tank so it's fully coated on all sides ) and then drain the excess. (That is the steps the directions will tell you as well). My experience was you will have a lot of it come back out when you drain the excess. Just be aware it has a 5-7 day cure time frame.

Krey

[shpielers]

+1 for por 15

[92xjunker]

Good stuff. It's so good that it is also used to coat jeep frames.