main jet question

[wolfie]

Hi everybody! I'm thinking about installing some Emgo pod filters to my bike, and I need suggestions on main jet size.

1981 GS850L
stock exhaust
current (stock?) jet size = 115
altitude = aprox 1000 ft above sea level.

Thanks

[KEITH KRAUSE]

I don't recommend changing to pods unless you also change to a free flow pipe. What for?
I can only guess but keep in mind that you'll have to richen the jet needle and pilot circuits too, not just the main. The main controls 3/4 to full throttle positions. The jet needle controls roughly 1/5 to 3/4 throttle. So the jet needle is actually used more in most riding conditions and is more important to jet correctly.
You probably have non-adjustable jet needles and will have to shim them up or get a pipe and buy a stage 3 jet kit that supplies the jet needles, etc.
You may get away with simple mixture screw adjustments to help the pilot circuit but you may need a larger pilot jet instead.
Then there's a possibility you'll need a larger air jet too. You may need to increase the vacuum ports to the diaphragm/piston chamber on your CV carbs too, to assist throttle response issues. Hard to say. You just have to test.
Always remove the float bowl vent lines when running pods too.
My point is, there's much more to jetting than just a main jet. Going with just pods, and inferior quality pods to be honest, isn't worth the trouble in my opinion. You can damage the engine if you re-jet incorrectly. You won't gain that much power without a free flow exhaust to compliment the pods. You'll lose a little low/mid-range grunt too.
As for your main jet question, I would guess 3 full sizes up and test. That would be 130. A full size = 5, a step = 2.5

[wolfie]

Thanks for the info. I haven't decided whether or not to try this mod, or to leave it stock. I like the sound of the stock exhaust, so I probably won't bother if I'll only get minimal gains, and a lot of headaches, by switching to the pods. Good info. Thank you very much. I was hoping that you would respond Keith, as you are a wealth of carb knowledge.

[KEITH KRAUSE]

You're welcome. I always try to give an honest answer based on what I "think" the poster is looking for.
Many truely believe that jetting is just changing the main and they're done.
If jetted correctly, you will notice some power increase at higher rpm's. An engine that breaths easier will make more power. But the Emgo's, though an improvement, are inferior to K&N's and the stock exhaust will certainly limit their freer flow ability further. Intake and exhaust really should compliment each other.
Also, with just pods, neither the stage 1 or stage 3 kits are designed for pod only mods. You'd then have to go with separate jets and it really can be a pain to dial it in.
You would probably pick up a few more HP but you'd most likely feel a small loss in low/mid-range torque. Not really worth the trouble in my opinion.