I have a problem that has stumped everyone I've talked to about this.
My R75 has something wrong with the idle mixture. Let me run through what is happening.
When setting the mixture the leaner I set the idle mixture the faster the idle. This happens on both sides. My thought was the idle air passage was blocked so I completely disassembled and cleaned the carbs, replacing all of the jets in the process.upon reassembly I have the exact same problem. The butterflies are correct.
Any ideas?
A blocked idle passage will give you none-to-very-little change in idle characteristics while you adjust it. So that's not it. Set the screws at 1-1/2 turns out and move on.
[An aside... I believe Bing uses a "pilot circuit" in which the mixture ratio is set by jets. What the screw does is vary the volume of the mixture. So turning the screw is not a simple lean-rich setting.]
1. In order to adjust the carbs, EVERYTHING else that is measurable has to be perfect. Perfect plugs, perfect plug wires, perfect timing, perfect valve settings, etc, etc.
2. Prime suspects within the carbs are air leaks due to cracked rubber parts. Replace the diaphragms and carb-to-head intake hoses.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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