If I want to enrichen my mid range do I need rich needle AND needle jet or just richer needle?
Around 6k rpms cruising my EGT went to 1250 real quick so I let off. Main seems just a size too large for max power and low end is great.
EDIT:
VM30 with 159-p-5 needle jet and 6F5 jet needle in richest position.
I believe the jet effects more higher up on the throttle but I'd personally move needle clip first. Then go up on jets as needed.
What carbs are you using?
VM30 with 159-p-5 needle jet and 6F5 jet needle
6k rpms is pretty high in the rev range and I have the clip in richest position.
Quote from: Czakky on August 17, 2020, 06:08:38 PM
I believe the jet effects more higher up rev range but I'd personally move needle clip first. Then go up on jets as needed.
What carbs are you using?
Sorry I was doing eight things at once. I edited my original response. I meant higher throttle position.... which is a strange way of putting it. But either way. Needles are way less linear how they are designed/shaped. I would play with needle jets first, but there are many smarter folks on here than me.
If you are lean at 7/8 throttle coming off a rich main you need a richer nozzle.
If you are lean 1/2 throttle you probably need a richer needle.
Drop a notch to rich your mixture. Raise a notch to lean it out. A lot of people start at the middle.
I was struggling with tuning my carbs, could not make it to the main jet. I kept on fouling plugs before getting to WOT and found that the remedy was to go up a notch from the 4th position (second from the bottom) to the 3rd (middle) position. Then I was able to properly jet to get to WOT.
Quote from: Alain2 on August 18, 2020, 11:25:20 AM
If you are lean at 7/8 throttle coming off a rich main you need a richer nozzle.
If you are lean 1/2 throttle you probably need a richer needle.
Are you sure that's correct. Larger needle jet has a proportionately larger effect at small throttle openings because the annular orifice is so small there and any change has a big effect whereas at WOT, the change in area is small compared to the baseline. That shows up on the Mikuni handbook as maximum impact at 25-30% throttle with zero effect at WOT.
Change in clip position has impact at slightly higher throttle "peaking" at 50% and still some impact almost all the way to WOT.
What I think the OP needs is a different needle with sharper second taper to richen up the 1/2 to 4/4 throttle. 6F5 is quite a lean top end. Try a 6F9 and see if that helps. It's a single taper but might get you close enough. If not, try 6DP1 which is much richer.
Quote from: teazer on August 18, 2020, 12:17:06 PM
Quote from: Alain2 on August 18, 2020, 11:25:20 AM
If you are lean at 7/8 throttle coming off a rich main you need a richer nozzle.
If you are lean 1/2 throttle you probably need a richer needle.
Are you sure that's correct. Larger needle jet has a proportionately larger effect at small throttle openings because the annular orifice is so small there and any change has a big effect whereas at WOT, the change in area is small compared to the baseline. That shows up on the Mikuni handbook as maximum impact at 25-30% throttle with zero effect at WOT.
Change in clip position has impact at slightly higher throttle "peaking" at 50% and still some impact almost all the way to WOT.
What I think the OP needs is a different needle with sharper second taper to richen up the 1/2 to 4/4 throttle. 6F5 is quite a lean top end. Try a 6F9 and see if that helps. It's a single taper but might get you close enough. If not, try 6DP1 which is much richer.
Let's try this:
If you are lean at 7/8 throttle coming off a rich main you need a richer needle .
If you are lean 1/4 - 1/2 throttle you probably need a richer nozzle.
Sorry about the confusion
Fellas my question was far more rudimentary and I think I've assumed the answer.
Let me ask a different way.
Do you change jet needle and needle jet in combo or can I simply swap jet needle only? Probably a stupid question that I believe I've found the answer to.
You can change them individually.
Alain2 is right.
Change just the needle if that's the change you want. If you don't have needle dimensions, PM me and I may have the spec's here. But try a 6F9 with your current needle jet and see how that changes things.