Motorcycle Repair: 1986 Honda Gl1200I, manifold vacuum, gold wings

Question
Hello Bill - hope you can help me. My '86 GL1200I misses and backfires in first, second and third gears with no load..just moving easily along the road, but it does not have a problem in fourth or fifth.  I understand there is a timing adjustment the motorcycle does once shifted from third to fourth. Is there some module I could inspect?

thanks

Answer
Tony, a Gold Wing is way out of my expertise, but I found this site, which may help http://www.goldwingfacts.com/forums/
Is this bike a fuel injected GL1200i or a GL1200I Interstate? Big difference in the possibilities between the two versions.

I did check the PARTS FISH site to see what's up with the fuel system setup and you may want to check the air cut valve system that is mounted on the center housing. If the diaphragm goes bad, you will have a big air leak that will cause backfiring and surging. This applies to the carburetor types, only, though.
The ignition timing is electronically controlled and not adjustable, like the good old days. The timing for carburetor models shouldn't have any kind of delay or gear sensor inputs, as far as I know... but I don't know much about these Gold Wings. The spark module has some kind of spark advance curve built into it, but w/o a manual it is hard to guess what the curve rate is or the effect in gears.

By the time you get the bike into 4th or 5th, the manifold vacuum signal to the fuel system is different than in lower gears, due to the load on the motor.

Bill Silver