Easy there fellas. I really do appreciate all of the help and attention that you kind folks are giving me. You guys are the best! No sense in getting our collective kinckers in a twist.
That said, some of this is my fault. I did leave out some details that may be adding to the confusion. One important one is that I soldered a piece of 1/8" tubing to my throttle cable after careful measurement to get it just right. Just right is within the range of the cable adjustment on the twist grip so that the slide can be all the way down (closed with the slide screw backed out) without there being any slack in the throttle cable. I paid close visual attention to the slide while setting up the throttle cable. Rest assured that the cable is not holding the throttle slightly open at all, while still having some adjustment in both directions, in the twist grip. These things expand and contract with ambient temperature. You always have to leave in a small degree of adjustment.
I agree that it is difficult to troubleshoot via an internet forum. It's so much easier to put your eyes and hands directly on the patient. I also think I understand how the enrichment control works. Off = lever up/plunger down. On = lever down/plunger up. Anyway, I suspect that I made all adjustments with the enrichment off.
If my understanding is correct, the more you turn out the air screw, the more you lean out the idle. The fact that I need >2 turns is an indicator that the pilot jet is too big. So in order to get the air screw closer to say 1.5 turns out, I will need to install a smaller pilot jet, which will effectively allow it to be properly dialed in with less turns on the the air screw. At least that's how I'm thinking it works. So do I understand this correctly or am I way off base?
-Ray
That said, some of this is my fault. I did leave out some details that may be adding to the confusion. One important one is that I soldered a piece of 1/8" tubing to my throttle cable after careful measurement to get it just right. Just right is within the range of the cable adjustment on the twist grip so that the slide can be all the way down (closed with the slide screw backed out) without there being any slack in the throttle cable. I paid close visual attention to the slide while setting up the throttle cable. Rest assured that the cable is not holding the throttle slightly open at all, while still having some adjustment in both directions, in the twist grip. These things expand and contract with ambient temperature. You always have to leave in a small degree of adjustment.
I agree that it is difficult to troubleshoot via an internet forum. It's so much easier to put your eyes and hands directly on the patient. I also think I understand how the enrichment control works. Off = lever up/plunger down. On = lever down/plunger up. Anyway, I suspect that I made all adjustments with the enrichment off.
If my understanding is correct, the more you turn out the air screw, the more you lean out the idle. The fact that I need >2 turns is an indicator that the pilot jet is too big. So in order to get the air screw closer to say 1.5 turns out, I will need to install a smaller pilot jet, which will effectively allow it to be properly dialed in with less turns on the the air screw. At least that's how I'm thinking it works. So do I understand this correctly or am I way off base?
-Ray
Two turns out on the air screw is OK. I think I said that above. When you start going MORE than two turns, is when you need to be looking at a smaller pilot jet. Notice, I said MORE than two turns.
I thought my throttle cable was set properly too. I thought that three times, as I removed the slide and re-soldered it three times. Just saying. And it wasn't my first Chikuni.
So get the 12.5 and if everything is as you say, you're golden! If not, you can disconnect your throttle cable and try to start it and see if idle acts the same. Personally, I'd do that first, but that's just my most recent fiasco with silver solder talking.
By the way, the attached guide is the best Mikuni tuning and troubleshooting guide you will find. I ran across it a few years ago, when I was adjusting my first Mikuni on a flathead Briggs, and found it quite helpful in understanding the curcuits and the way in which they interact.
We're all friends here.
Edit: @delray as I recall, you wondered what the adjustable exhaust baffle would do to my carb tune? I forgot to mention in my build thread. Open, it is a bit more crisp. However, a main jet increase/decrease was as bad for either setting, as was a metering needle setting. So there is a slight difference, but not enough of a difference to be able to adjust the carb for it. Idle doesn't change. Big difference in noise though!
http://www.iwt.com.au/mikunicarb.htm