How can fiddling only with Pilot Air screws cripple my gs850

[RandyRex]

Question: What, exactly, does the Pilot Fuel Screw do? The reason I'm asking is that I cannot get my #1 spark plug to even begin to gather some soot, no matter how far in/out I turn the Pilot air Screw, so I am wondering if turning the Pilot Fuel Screw out a little bit will add some more fuel to the cylinder. Does this sound valid? I know that Suzuki is supposed to set these at the factory and paint them, to avoid excess EPA penalty points, but I care not for painted "don't touch me" screws, if my mix is too lean, regardless of the "Air Screw" settings ...

[Big T]

You are correct on that the Pilot fuel screw will add gas by turning it out more
You are incorrect if you think it will add more gas past idle. The pilot circuit has little affect past 1/4 throttle

[RandyRex]

You are correct on that the Pilot fuel screw will add gas by turning it out more
You are incorrect if you think it will add more gas past idle. The pilot circuit has little affect past 1/4 throttle

Understood, oh sage of all that is GS it's within the first 1/4-idle circuit that I seem to be having trouble, and today cranked the Fuel screw out 1/16 and PRESTO! some soot on #1. I had been doing the old "avert thine eyes, (look not upon the factory-set, painted, taboo screws of EPA defiance ...)" that was plastered all over every intergoogles reference I could find, so ... (naturally) I had to assume that this was the choke point. Thanks, I kinda started thinking that those lil fellas worked in tandem. middle and upper jets are fine, now, in fact once past 1/4 throttle, she wants to roar into life, but that won't cut the cheese in my little podunk I'd catch a felonious ticket 'round here ... and within the first 1/8th to 1/4, it was bogging, coughing, (due to bodged electrics .... like delta condensor connections and filed points .... you know the story ...) so, I started to look at that circuit and thought "hey .... I bet those FUEL Pilots could be my buddies ..." cheers mates

[KEITH KRAUSE]

I didn't read all the replies. I hope this helps.
The "marbles" sound suggests a lean condition. The pilot circuit has some affect but it's the jet needle position that contributes the most here during typical throttle use, though the main jet factors in if you're fully opening the throttle and then hear the pinging.
You said you have pods. Do you also have a 4-1 exhaust or stock? If stock, the jetting is difficult to get right because pods and a stock exhaust are a poor flow match.
I read here that the stock main jet size is 102.5. If pods only, you'll need mains between 120 and 125, add 5 for a quality 4-1 exhaust. Place the jet needles e-clip in the 4th position from the top. Be SURE the pilot jets are STOCK size. Set the pilot fuel screws at 1 turn out from lightly seated. Set the side air screws at 1 3/4 turns out and then fine tune using the highest rpm method, while being sure to use a base idle of no higher than 1,100 rpm's. Re-check/adjust float levels. Re-check/adjust your advance timing. Use the correct octane gas. Be sure the pods are properly oiled if they are supposed to be oiled. These are just basic suggestions that I know will not allow pinging and the bike will not be excessively lean or rich. You may need to go up or down a size on the mains. You may need to further richen the jet needle positions to "4 1/2" or position 5. You may need to slightly tweak the pilot fuel and air screw settings. Testing: Clean plugs or new, correct gap set. Jet needles: do a run at 1/2 throttle, chop off and check the plug colors. Main jets: run at full throttle, chop off and check the plugs. Pilot circuit: Pay attention to how it starts and how long to warm up. After fully warm, let it idle at 1,000-1,100 rpm's a minute, moderately blip the throttle, exhaust should be clear/no dark exhaust showing. Rpm's shouldn't "hang" momentarily but return smoothly. Opening the throttle just above idle there should be no hesitation or bog. Again, if you're mixing pods with a stock exhaust, you may have to accept several carb related issues.
So much more to making a bike run well. Valve clearances, correct voltages throughout the system, carbs/intake in good condition.....

[KEITH KRAUSE]

Also. Double check your jet needle assembly with a parts illustration. Be sure every part is there and in the correct position.

[RandyRex]

I didn't read all the replies. I hope this helps.
The "marbles" sound suggests a lean condition. The pilot circuit has some affect but it's the jet needle position that contributes the most here during typical throttle use, though the main jet factors in if you're fully opening the throttle and then hear the pinging.
You said you have pods. Do you also have a 4-1 exhaust or stock? If stock, the jetting is difficult to get right because pods and a stock exhaust are a poor flow match.
I read here that the stock main jet size is 102.5. If pods only, you'll need mains between 120 and 125, add 5 for a quality 4-1 exhaust. Place the jet needles e-clip in the 4th position from the top. Be SURE the pilot jets are STOCK size. Set the pilot fuel screws at 1 turn out from lightly seated. Set the side air screws at 1 3/4 turns out and then fine tune using the highest rpm method, while being sure to use a base idle of no higher than 1,100 rpm's. Re-check/adjust float levels. Re-check/adjust your advance timing. Use the correct octane gas. Be sure the pods are properly oiled if they are supposed to be oiled. These are just basic suggestions that I know will not allow pinging and the bike will not be excessively lean or rich. You may need to go up or down a size on the mains. You may need to further richen the jet needle positions to "4 1/2" or position 5. You may need to slightly tweak the pilot fuel and air screw settings. Testing: Clean plugs or new, correct gap set. Jet needles: do a run at 1/2 throttle, chop off and check the plug colors. Main jets: run at full throttle, chop off and check the plugs. Pilot circuit: Pay attention to how it starts and how long to warm up. After fully warm, let it idle at 1,000-1,100 rpm's a minute, moderately blip the throttle, exhaust should be clear/no dark exhaust showing. Rpm's shouldn't "hang" momentarily but return smoothly. Opening the throttle just above idle there should be no hesitation or bog. Again, if you're mixing pods with a stock exhaust, you may have to accept several carb related issues.
So much more to making a bike run well. Valve clearances, correct voltages throughout the system, carbs/intake in good condition.....

Excellent advice, sir, thank you. 4 into 2 stock exhaust, just put 130s into her and currently have the needle set at notch 3, which has given her a nicer handoff from the pilots, 4 isn't out of the running, yet. I'm not sure how to feel about this episode, as I bought a bike that I was assured would make a 600 mile trip, I heard issues, but never imagined that it would become an odyssey .. however, I've been forced to learn all the ins n outs of carbs a la motorcycle. I had a laymans understanding of car carbs, but it was shallow. Now, as a result of this fiasco, I've actually learned the stuff I should have learnt decades ago ... and, I'd avoided the Pilot Fuel Screw, which I now know was one of the trouble areas, being as they were not being adjusted by anyone who had delved into this bike .. after crossing The Point Of No Return and becoming an EPA outlaw, I've gotten the balanced report from the plugs that I wasn't seeing. 1 turn out, on the Fuel thingies? Not 1 1/2? I know the Air thingies need to be at 1 1/2 to 1 1 3/4, but I still need to finish dialing her in, and until I get the proper sets of points that I expect should arrive Tuesday, I'm kinda stopped in muh tracks Between youse guys and all the technical schtuff in here, and 2 months of "I quit driving trucks and got lazy", I was able to get it all together in my head and I'm on the right track now.

[OldVet66]

I can certainly sympathize with your problems. When I first got my bike I bit on the advertisements from Wired George and got a set of carburetors that instead of being built for my bike were super lean so I know the lean detonation "marbles" sound well. It resulted in a overheating motor that has probably taken permanent damage. Fortunately I had a parts bike with a 4,500 mile motor that I swapped into it, and learned from Keith and others how to rebuild the pristine carburetors that were on that motor. The pods and pipes were another story, but neither bike had an air box, and that was the way I got both bikes, the parts bike with very bad exhaust pipes and the original bike with a V&H 4-1 exhaust. I learned that end of the rejetting equation and have had a very nice running bike for many years.

[KEITH KRAUSE]

Excellent advice, sir, thank you. 4 into 2 stock exhaust, just put 130s into her and currently have the needle set at notch 3, which has given her a nicer handoff from the pilots, 4 isn't out of the running, yet. 1 turn out, on the Fuel thingies? Not 1 1/2? I know the Air thingies need to be at 1 1/2 to 1 1 3/4

OK, stock exhaust. It's difficult to give spot on jetting advice when you combine pods with a stock exhaust. They're a poor flow match. "IF" your jet needles are factory and the factory set them at position 2 from the top and the jet needle nylon spacers are in the correct assembly order, then raising the needles 1 position is generally not enough for the pods. But run the bike as I said at 1/3 to 1/2 throttle, chop off, and do what the plugs and performance say to. Run the bike at a constant speed in 5th gear, level or uphill, about 65-70 mph and pay attention to any surging feeling (lean condition). Every time you change or disturb the jet needles position or assembly, you MUST at least do a careful bench synch of the slides. Even when careful, you'll generally notice 1, or most often, 2 carbs with higher/lower vacuum than the others when you hook up with a quality synch tool, such as the Carbtune Pro. Without a good synch with a vacuum tool, jetting is more difficult and you cannot trust the plug reads and the testing results.
As for the pilot fuel screw and side air screw settings, there is no exact setting that works best for all bikes. You set them to what works best for your bike and it's state of tune, your elevation/climate. In general, the factory set your pilot fuel screws in the range of 1/2 to 1 turn out from lightly seated, with approx' 3/4 out being very common, at least that's my experience. They're very sensitive to adjustments. I'd allow that 1 turn out as a fair starting point. Fine tuning will almost always be needed. To best test the pilot circuit with as little as possible over-lap from the jet needles, ride the bike at lower speeds and keep the throttle position at less than 1/4. The side air screws are simple to find that sweet spot by following the highest rpm method. ALL other tuning must be correct before fine tuning the jetting. For the carbs, float level is critical. Also, all jetting components must be in good condition. If so, then initially set the side air screws to 1 3/4 turns out and the pilot fuel screws to 1 turn out. Fully warm up the bike on the centerstand, set idle at 1,000 rpm's. Start at any side air screw. Turn the screw in or out slowly until you achieve the highest rpm. Then, lower the rpm's to the base idle of 1,000 rpm's by adjusting the throttle adjuster knob underneath. Then go to the next screw and do the same thing. Repeat until all 4 are set. Do not try to adjust the air screws at rpm's higher than suggested. It shouldn't take much time, but place a fan on the engine to avoid over-heating.
I forgot to mention, REMOVE the 2 float bowl vent lines and leave the vents open to breath. This is mandatory per Dynojet's stage 3 jetting kits (pods and freer flowing exhaust). Results may vary, but leaving the float bowl vent lines on will result in varying degrees of fuel starvation when running quality pods. I can't say how your stock exhaust affects things in this case, but the change in the intake is significant enough to require removing the vent lines. Travelling at higher speeds and/or windy conditions makes the fuel starvation more noticeable.

[KEITH KRAUSE]

Remember, the pilot fuel screws are used to assist the pilot jet. They provide for fine tuning each cylinder. Because there are differences in each cylinder, such as compresssion, you will very often find that your final screw adjustments are different for each cylinder. So 1 turn out may work well for one cylinder, but 1/2 or 3/4 turn out works best at another cylinder.

[RandyRex]

I can certainly sympathize with your problems. When I first got my bike I bit on the advertisements from Wired George and got a set of carburetors that instead of being built for my bike were super lean so I know the lean detonation "marbles" sound well. It resulted in a overheating motor that has probably taken permanent damage. Fortunately I had a parts bike with a 4,500 mile motor that I swapped into it, and learned from Keith and others how to rebuild the pristine carburetors that were on that motor. The pods and pipes were another story, but neither bike had an air box, and that was the way I got both bikes, the parts bike with very bad exhaust pipes and the original bike with a V&H 4-1 exhaust. I learned that end of the rejetting equation and have had a very nice running bike for many years.

She might have taken some damage, but I think it's not enough to tell, I don't plan on racing her, so am hoping to get her running as is, and not even have to think about getting into the motor or having to find a swapper. I hear no indications of loose bearings or rings, so am optimistic for her. Thanks for the response. I think it's a telling thing that I went to 2 shops, with adequate symptoms and none of them even looked at the points ...

[RandyRex]

OK, stock exhaust. It's difficult to give spot on jetting advice when you combine pods with a stock exhaust. They're a poor flow match. "IF" your jet needles are factory and the factory set them at position 2 from the top and the jet needle nylon spacers are in the correct assembly order, then raising the needles 1 position is generally not enough for the pods. But run the bike as I said at 1/3 to 1/2 throttle, chop off, and do what the plugs and performance say to. Run the bike at a constant speed in 5th gear, level or uphill, about 65-70 mph and pay attention to any surging feeling (lean condition). Every time you change or disturb the jet needles position or assembly, you MUST at least do a careful bench synch of the slides. Even when careful, you'll generally notice 1, or most often, 2 carbs with higher/lower vacuum than the others when you hook up with a quality synch tool, such as the Carbtune Pro. Without a good synch with a vacuum tool, jetting is more difficult and you cannot trust the plug reads and the testing results.
As for the pilot fuel screw and side air screw settings, there is no exact setting that works best for all bikes. You set them to what works best for your bike and it's state of tune, your elevation/climate. In general, the factory set your pilot fuel screws in the range of 1/2 to 1 turn out from lightly seated, with approx' 3/4 out being very common, at least that's my experience. They're very sensitive to adjustments. I'd allow that 1 turn out as a fair starting point. Fine tuning will almost always be needed. To best test the pilot circuit with as little as possible over-lap from the jet needles, ride the bike at lower speeds and keep the throttle position at less than 1/4. The side air screws are simple to find that sweet spot by following the highest rpm method. ALL other tuning must be correct before fine tuning the jetting. For the carbs, float level is critical. Also, all jetting components must be in good condition. If so, then initially set the side air screws to 1 3/4 turns out and the pilot fuel screws to 1 turn out. Fully warm up the bike on the centerstand, set idle at 1,000 rpm's. Start at any side air screw. Turn the screw in or out slowly until you achieve the highest rpm. Then, lower the rpm's to the base idle of 1,000 rpm's by adjusting the throttle adjuster knob underneath. Then go to the next screw and do the same thing. Repeat until all 4 are set. Do not try to adjust the air screws at rpm's higher than suggested. It shouldn't take much time, but place a fan on the engine to avoid over-heating.
I forgot to mention, REMOVE the 2 float bowl vent lines and leave the vents open to breath. This is mandatory per Dynojet's stage 3 jetting kits (pods and freer flowing exhaust). Results may vary, but leaving the float bowl vent lines on will result in varying degrees of fuel starvation when running quality pods. I can't say how your stock exhaust affects things in this case, but the change in the intake is significant enough to require removing the vent lines. Travelling at higher speeds and/or windy conditions makes the fuel starvation more noticeable.

Thank you, sir, I will follow this, once I've actually got some good points and condensers, the Retro Motorcycle idiot refuses to send me the correct points as an exchange, sent me a refund that Pay-pal made disappear by attributing it to an old card that I no longer possess, against my stated desire that he simply send me the correct points, which I know he had. So, at the moment, I'm out of cash and parts ...

[KEITH KRAUSE]

Working on an older bike that's generally more simple than the newer bikes, should be easy for a mechanic. But many mechanics today have no experience with older electrical systems, carbs, etc. The GSResources is a far better place to go for help. If you follow what the members here say, you'll more often than not get your bike running well. But if you take short cuts and don't spend the time that's necessary to do a complete job, then you'll get frustrated. It's not easy to diagnose a problem when you have to factor in maybe years of poor/unknown maintenance, neglect or abuse by who knows how many previous owners, hack work, parts mixed.....
Old bikes, old ANYTHING, are going to require some effort to make them run well. Takes a lot of patience and sometimes money.

[RandyRex]

Working on an older bike that's generally more simple than the newer bikes, should be easy for a mechanic. But many mechanics today have no experience with older electrical systems, carbs, etc. The GSResources is a far better place to go for help. If you follow what the members here say, you'll more often than not get your bike running well. But if you take short cuts and don't spend the time that's necessary to do a complete job, then you'll get frustrated. It's not easy to diagnose a problem when you have to factor in maybe years of poor/unknown maintenance, neglect or abuse by who knows how many previous owners, hack work, parts mixed.....
Old bikes, old ANYTHING, are going to require some effort to make them run well. Takes a lot of patience and sometimes money.

That it does =D

[chuck hahn]

I would like to point out that although raising the needle solved the symptom, the first thing should have been check float hts AND AND wet fuel levels in each carb. Incorrect float hts and incorrect wet fuel levels will mimick what he experienced. And note that even though the floats are "within specs" doesnt automatically mean the fuel level is correct. So my questions to myself would now be was the float hts right from the beginning and what were the fuel levels before I raised the needles?? Did I really need to raise the needles or did i need to tweek float the so i was getting correct fuel levels in the bowls????

[GSXR7ED]

Working on an older bike that's generally more simple than the newer bikes, should be easy for a mechanic. But many mechanics today have no experience with older electrical systems, carbs, etc. The GSResources is a far better place to go for help. If you follow what the members here say, you'll more often than not get your bike running well. But if you take short cuts and don't spend the time that's necessary to do a complete job, then you'll get frustrated. It's not easy to diagnose a problem when you have to factor in maybe years of poor/unknown maintenance, neglect or abuse by who knows how many previous owners, hack work, parts mixed.....
Old bikes, old ANYTHING, are going to require some effort to make them run well. Takes a lot of patience and sometimes money.

+1

There's another thread currently going on where this statement applies.

Back to the original thread topic.

Glad you got your Carbs properly identified and getting the assistance from members here.

Ed