J
Joe Garfield
Guest
(Valves shimmed and carbs fully rebuilt this year, but carbs not yet synced)
Yesterday I adjusted my idle mixture using the RPM method. It was a pretty hot day (low 90s F) and I did the adjustment outside using a fan after a short ride to warm it up. I did this adjustment at an idle of 1050 rpm. At the end of my initial adjustment I found that I could turn the screw 1/2 turn in either direction without affecting the RPM, so I figured that was a good place to be. I took the bike for a ride and found the idle, and just about everything that happens at low RPM, to be silky smooth. The bike started immediately and easily. However it felt like the bike lagged power when nailing the throttle. I suck at keeping track of this stuff, so I don't know exactly how many turns out the screws are. They were all pretty consistent, and my guess is they're at ~2.25 to 2.5 turns out.
I went online and re-read the procedure and found that I should have leaned out the mixture as much as possible without a drop in RPM. I also read about using a lower RPM just for the adjustment, So I re-adjusted the mixture at ~900rpm and ended up about 3/8-1/2 turn in from where I was before - this was as lean as I could make it w/o dropping from highest RPM. I took the bike for a ride again and found the power was awesome. I would say the bike wasn't quite as silky smooth, but really hard to perceive a difference.
My exhaust 'popped' before any of the adjustments, didn't seem to pop after the first, and pops again after the second - but I do have a small exhaust header leak at #1.
Today I fired up the bike, it's about 10 degrees cooler. After a short minute I let off the choke and the RPMs were about 100-150 lower than where I set it yesterday. This led me to think I might have set the mixture a little lean - likely due to the temp of the bike and the temp outside. While I was out I adjusted the idle screw back up to ~1050rpm.
I don't notice any 'issues' when giving it throttle - it goes right up to 3,500 and quickly settles back down to 1050 (RPM does fall just slightly faster from 3500-2500 than it does from 2500-1000), and there are no signs of the bike wanting to quit or sputter on accel/decel.
I didn't adjust any 'air screws' as I don't believe my bike has them. What I'm curious about is if I could have the mixture screws lean but the idle adjustment rich, or something of that sort. Or maybe I just need to back out 1/4 turn due to the heat yesterday. I read about what happens when things are grossly maladjusted, but I didn't see any detailed descriptions of how to do the really fine tuning.
Thanks for readin and any advice/suggestions, and sorry this got so long!
Edit: I'm also curious how worn piston rings and valve seals can affect all this. Mine are within spec but at the low end and the bike uses oil.
Yesterday I adjusted my idle mixture using the RPM method. It was a pretty hot day (low 90s F) and I did the adjustment outside using a fan after a short ride to warm it up. I did this adjustment at an idle of 1050 rpm. At the end of my initial adjustment I found that I could turn the screw 1/2 turn in either direction without affecting the RPM, so I figured that was a good place to be. I took the bike for a ride and found the idle, and just about everything that happens at low RPM, to be silky smooth. The bike started immediately and easily. However it felt like the bike lagged power when nailing the throttle. I suck at keeping track of this stuff, so I don't know exactly how many turns out the screws are. They were all pretty consistent, and my guess is they're at ~2.25 to 2.5 turns out.
I went online and re-read the procedure and found that I should have leaned out the mixture as much as possible without a drop in RPM. I also read about using a lower RPM just for the adjustment, So I re-adjusted the mixture at ~900rpm and ended up about 3/8-1/2 turn in from where I was before - this was as lean as I could make it w/o dropping from highest RPM. I took the bike for a ride again and found the power was awesome. I would say the bike wasn't quite as silky smooth, but really hard to perceive a difference.
My exhaust 'popped' before any of the adjustments, didn't seem to pop after the first, and pops again after the second - but I do have a small exhaust header leak at #1.
Today I fired up the bike, it's about 10 degrees cooler. After a short minute I let off the choke and the RPMs were about 100-150 lower than where I set it yesterday. This led me to think I might have set the mixture a little lean - likely due to the temp of the bike and the temp outside. While I was out I adjusted the idle screw back up to ~1050rpm.
I don't notice any 'issues' when giving it throttle - it goes right up to 3,500 and quickly settles back down to 1050 (RPM does fall just slightly faster from 3500-2500 than it does from 2500-1000), and there are no signs of the bike wanting to quit or sputter on accel/decel.
I didn't adjust any 'air screws' as I don't believe my bike has them. What I'm curious about is if I could have the mixture screws lean but the idle adjustment rich, or something of that sort. Or maybe I just need to back out 1/4 turn due to the heat yesterday. I read about what happens when things are grossly maladjusted, but I didn't see any detailed descriptions of how to do the really fine tuning.
Thanks for readin and any advice/suggestions, and sorry this got so long!
Edit: I'm also curious how worn piston rings and valve seals can affect all this. Mine are within spec but at the low end and the bike uses oil.
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