i have an 85 gl 1200 interstate with 62000 miles and having some confusing problems which i hope someone has some ideas where to go next.
3 months ago was starting to have problems with choke,when fully choked would increase idle to about 3000 rpm, then it started to increase less and less to about 200 rpm increase then cable broke, thought that was the problem, replaced cable and still had same problems as before.
The main problems are when started without choke will idle at 200-300 rpm when choke on smells really rich but wont increase idle. when it gets to operating temp idle set at 1000-1100 rpm all is good.( i wish) when taken on a 15-20 min run on the interstate idle increases to 1800-2000 rpm lower idle back to 1000-1100 rpm and drive in city idle drops to 500-700 rpm, rest to 1000-1100 rpm let cool, restart without choke will idle at 200-300 rpm sometimes choke on will increase to 500rpm.
Things that i have done are:
i will always run 2-4 oz of seafoam in every other tank of gas, i quit putting it in for 5 fill ups, made no difference.
Removed carbs cleaned, no difference, replaced air filter, fuel filter,fuel lines, vacuum lines, then did a sync no help same problems.
Removed carbs again rebuilt with kits from randaks, resynced, no difference
Replaced manifold "O" rings, slow air cutoff checked slides and diaphragms, removed and cleaned chokes on carb, resynced no difference.
Removed carbs boiled in distilled water let soak in carb cleaner rechecked slides and diaphragms checked all the little ports in carbs, jets, floats, changed spark plugs, resynced, stripped all screws had to rethread and install new screws, still same thing.
I am hoping that somebody might have a place to goto next