I haven't forgotten about this but my jets still haven't arrived and I'm away for 3 weeks now. Hopefully they will be there when I get back
Okay, FINALLY got the new jets. Running better but not cured. Bikes wants to pick the front wheel up in first and second now but still not happy at very low throttle cruise around mid-range. Spoke to a mechanic and he believes it could still be rich and suggested dropping the needle to see if it helps. Will give that a go soon.
Dropped the needle and it's a little better. I've got one more slot that I can go to. Are the needles the same between all the jets or does each jet have a matching one? It's riding much better that when I started. It's really just the very low throttle, steady state break up that's left i.e, say you're in 3rd at low RPM, you give it about 1/5th throttle and gently accelerate. At around the mid point in RPM, just as the speed levels out and you reach steady speed, it will break up. Give it a tiny bit more throttle and it's back to normal. So any amount of acceleration is fine but steady cruise with the throttle just cracked and it will break up. Anyone else seen this? I might pull some more idle mixture from it and see. I think if anything, it's still rich, rather than lean.
Been working on a few other things but figured I would have a crack at finishing this. Pulled another half turn from the idle jets and it was nearly perfect. Best it's ever ridden. Stopped on my ride and opened it up as I set off and it picked the front wheel straight up. It's never done that before. So along I ride for about 45 minutes until it turns to shit again, got home and had fuel from the overflow. Since I have messed around with the levels when troubleshooting and I've tried adjusting these a few times now, I've just bitten the bullet and ordered two new float assemblies. I'm guessing they should be correctly set from factory?
Okay, new floats in and no overflow. It still starts to miss in the midrange at extremely small throttle openings. I've been pulling idle jet from it but no significant change. Would it be the pilot jet operating in this area?
Yes, try closing/opening the pilot screws by ¼ turn and see if it makes a difference. My money would be on slightly too rich.
Pilot jets / idle jets, they are the same thing and the adjustment is the only mixture adjustment on the carbs. Your's wouldn't have caps over them. This image is from a Suzuki. Try adjusting by ¼ turn increments and note any change. You may have adjust the idle speed to suit.
Cool, thanks. I've been adjusting that but it doesn't seem to change much with this problem. I thought there were three jets, idle, pilot and main? The idle being the only adjustable one and the other two being accessed with the float off.
Your other option is to try dropping or raising the needle by a notch. I think this might affect the running at wider throttle openings though but could be worth trying. I know you have already replaced the emulsion tubes (needle jets) and the needles so these are unlikely to be the cause. When I had a 900ss with the Mikunis it developed a flat spot at small throttle openings, it would hesitate just as the throttle was opened. I could tune this out by adjusting pilot mixture to be leaner but that buggered up the tick over. I had nearly new Factory Pro needles fitted so replaced the emulsion tubes only and all was fine again. This is what led me to think that the mixture on yours isn't right on the transition from closed to small throttle openings. There are 4 jets; the main jet, the emulsion tube (or needle jet) and the pilot jet (also sometimes known as the pilot jet) and also a starter jet (operated by the choke lever). The idle adjustment varies the amount of air getting to the pilot circuit.
Cool, thanks. I've already dropped the main needle a notch. I'll keep dialling down the idle mixture until it runs noticeably worse and see if that changes anything. I'm also wondering if maybe it's a carb synching issue. As far as I can tell, I've fixed all the air leaks bit I still couldn't get them perfectly synced at idle. I didn't change the emulsion tubes or needles. Just the main jets. I know they can wear quickly but the bikes has 7k miles on it and I had a very close look at the tubes and needles and there a no signs of rubbing.
Okay, so I read the idle jets are 40 as standard, so I ordered 37.5's and 35's. Pulled them today and they had 42.5's in them. Put the 37.5's in and it's the best it's run yet. I'd almost call it fixed. Just need to get the idle mixture screws dialled in now.
