1977 gs550 lean factory jetting?

[Guest]

I've got a 1977 gs550 with stock air box, air filter and pipes. I currently run a size 80 main jet, which I believe is also stock. I've read a thread that later models (82) were lean from the factory, but I'm not sure if that's the case with the older bikes.

Do any of you know if a 77 would also benefit by going to a 82.5 or 85 main jet on a stock setup, especially since gas today is a little bit lower octane? I'm only about 700 ft above sea level.

Thanks for sharing the knowledge

[JJ]

I've got a 1977 gs550 with stock air box, air filter and pipes. I currently run a size 80 main jet, which I believe is also stock. I've read a thread that later models (82) were lean from the factory, but I'm not sure if that's the case with the older bikes.

Do any of you know if a 77 would also benefit by going to a 82.5 or 85 main jet on a stock setup, especially since gas today is a little bit lower octane? I'm only about 700 ft above sea level.

Thanks for sharing the knowledge

First off, welcome to the greatest motorcycle forum on Earth.

Is it running badly? Low on power? Popping on decel? Do the plugs look lean?

If it isn't broken, don't fix it.

[tkent02]

What he said, but mostly it wasn't the main jets that needed to go bigger on the later bikes, it was the jet needle and the pilot circuit that controls the mixture just off idle. Mostly the mains were OK.
One more question, does your fuel consumption seem about right for how you ride? If it's too lean the mileage will suck.

[mralexan]

That makes sense to me. No it is running fine actually around idle and up to mid throttle position. When I get up to higher RPMs near full throttle, it does seem to drop off in power well before I get to red line. Probably should have mentioned that.