How can fiddling only with Pilot Air screws cripple my gs850

[Guest]

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.

 

[Guest]

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

 

[rphillips]

Bike shops??? The mechanics at many shops aren't as old as our bikes. A mechanic that was 20 yr. old, when your bike was new is now 60 yr. old. Just think how many of today's mechanics have never seen a set of points, they are completely lost working on a 79 GS750, like I would be working on a brand new 2019 Suzuki Hayabusa. For us old bike guys, Older mechanics should be better. Just my opinion