Stock 82 GS850 jet up

[79xs]

I work mostly on Yamaha bikes, but i'm helping a buddy get his 82 GS850 going. It runs alright, but as everyone knows the bikes were jetted within an inch of their life from the factory.

Stock jets are 40 pilot and 115 main.... has anyone had luck with just throwing 42.5 pilots and 117.5 or 120 mains at it to keep the thing happy? I mean I have everything else tuned up fine.. intake boots, o-rings, sealed airbox, but you can tell its running like a california bike. You just look at the bike wrong and a .000001 micron air leak makes it run like crap. I would like there to be some gap for error. I pretty much want to de-EPA the bike. Any views?

[tkent02]

They made them lean at low power, not wide open as the EPA tests were done at low power...
I'd try the bigger pilot and nothing else first time around, just for a starter.
But that's just a wild ass guess.

[7981GS]

Keep the #40 pilot jet and go with the 117.5's.
Fatten-up the fuel screws a little and see how you like it.
If you have to, you could raise the jet needle .47-.52mm by substituting the necessary 3mm flat washers for the factory plastic spacer. (2.50mm)

Hope that helps!

Eric

[twr1776]

I am running that set up on my 850 and it has been fine per plug reads.

Where do you have the pilot mix screw set at? I did richen mine up slightly on the pilot circuit and if I did anything else I would shim the needle with one or two washers at most to also richen up the mid-range slightly. The main jet seems fine and Suzuki ran the 115 jet size on the 850, 1000, and 1100 two valve motors with CV carbs and stock airbox/stock exhaust set ups.

Some will bump the pilot only to 42.5 and shim the stock needle on the 1000/1100 motors but I have not seen anyone do it on the 850.

Richer is never bad so if you do decide to go one up on the pilot/main for the 850 let us know what your plugs read.