So I'm rejetting my 2001 GS500. Per the wiki "The pilot jet and idle screw affect the mixture at idle. Adding washers to the needle jet affects the mixture at partial throttle. The main jet affects the mixture at or near full throttle. Larger jets, or more washers on the needle jet, will make your bike run richer within the corresponding throttle range. "
So my question is, what does the mid-main jet do? Also does anyone have a good picture of where to put the washers on the needle jet? The instructions linked in the wiki left me a bit confused.
Also I know you're supposed to adjust the idle airscrews to set the idle to ~1200 RPMs when you're all done. But what if your throttle idle screw (the big one inbetween the carbs) is off? How do I know if it's off? Cause I could close up my pilot air screws and use that to adjust the idle to 1200 or back it out and then open up the pilot airscrews more. How do I know where each is supposed to be? Currently the pilot airscrews are at ~3.5 turns out and I have the idle set to ~1400.
Quote from: MotoSig on April 17, 2018, 07:53:11 PM
Cause I could close up my pilot air screws and use that to adjust the idle to 1200 or back it out and then open up the pilot airscrews more. How do I know where each is supposed to be? Currently the pilot airscrews are at ~3.5 turns out and I have the idle set to ~1400.
Those are not "air screws" FYI, they actually control the position of a needle in the pilot jet so they are more accurately "fuel" metering screws.
Anyway,
You have the idle set too high (throttle stop screw), and you have the pilot mixture needles set outside their usable range. Turn the pilot needle screws back in to 2.5 turns from closed and back the throttle stop all the way off so the throttle closes fully at idle. Start the bike on choke, ride for about 1-2 minutes and gradually turn off choke, then RIDE FOR LIKE 20 MORE MINUTES, then assess the idle mixture (pilot needle screws). While the engine is still hot and running, start with the pilot needles about 1.5 turns out, then back them out 1/4 turn at a time until the idle stops increasing. If you go past three turns out then you've gone too far and you need to jet up, just leave them at 3 turns out or pull the carbs and rejet. Once you get the idle MIXTURE set, then go ride some more and get used to tweaking the throttle stop when you are sitting stopped. Ride a bit, make sure the bike is fully warm, then stop and assess the idle speed. If it takes more than about 1 second to return to idle after revving, then the throttle stop is too high ("idle speed" is too high). Adjust the throttle stop until it just returns to idle in about 1 second or less. It will idle at whatever speed it idles at, that is controlled by an air inlet in the throat of the carb, not the throttle position. On my bike it's about 1100 rpm when fully warmed. You don't really set the idle speed with that throttle stop screw. If you turn it in high enough to get it to "idle" above about 1200 rpm then you are not really letting the bike idle, it's just holding the throttle partly open and it's running on main (or middle) jet and therefore pilot mixture adjustments will have limited or no effect.
Awesome thanks. :thumb:
So what does the mid-main jet do if the needle jet affects it at partial throttle?
Also do you have a good explanation/pictures of where to put the washers on the needle jet?
I don't know what you mean by "needle jet". Adding washers as mentioned is on the NEEDLE, not on any jet. It causes the needle position to be moved in relation to the slide. There are good instructions on how to do this in the wiki IIRC. Otherwise all over the internet, good videos on youtube, etc. I've never done it myself because there appears to be no need.
You never go from only pilot to then mid to then main. There's always bleed and overlap.