Idle issues... yippe

So as the title would suggest my bike is having some issues with idling. Ill apologize in advance for the word vomit you are about to read, and if this has been a topic discussed many time before, i couldn't find much with the search feature.

Ive got an '85 Maxim X, 700cc watercooled with that sweet 5 valve head. It is 99% bone stock, just has a uni foam air filter that the previous owner installed(might be my whole issue). The issue im having is with the idle, it either doesn't want to start and idle until its warm, or it idles at the 1100rpm prescribed by the decal in the side cover and then idles at 2500rpm when warm. The difference between the two happens when i play with the idle screw on the bottom of the carb rack, it idles fine and then starts racing when i adjust it while cold and then the opposite when i adjust it down once it warms up. I cant get it to find a happy medium for the life of me.

Ive had the carbs out, inspected the insides of the carbs, they were fantastically clean on the inside, and did a bench sync while i had em out. When i put them back in the bike, it pulled the same stunt as before i took em out. I did check for vacuum leaks while it was running by spraying the intake boots/carbs with brakeclean and nothing on that front, everything is sealed. At this point im thinking that it might either be from the aftermarket airfilter/stock jets (all of them were the factory sizes when i looked) or something is wrong with the carbs.

I will add in here at the end that it is only an issue at idle. The bike pulls like demon and doesn't have any flat spots through the rev range. The sparkplugs also have a color that indicates its not running too lean or too rich, was a nice toasty brown when i checked

I appreciate you reading all the way to the end and doubly so if you can offer this noob to carb stuff any advice on how to remedy the old girls problems.

 

Welcome to the forum.

Looks like you have done some good troubleshooting of the issue so far. Love them 700X's, just a little cramped riding position for my legs. They are great bikes and like you mentioned, man they run out well.

Throttle body seals might be an issue. Don't spray the carbs with brake cleaner or any corrosive cleaner. If the throttle seals get hit with cleaner, they are rubber, and it might worsen the issue. Starter fluid or other no corrosive spray that is flammable is best. There are "O" rings on the sides of the throttle shaft that moves the flies. If they crack or are bad, there is your vacuum leak.

The only other missed play would be the choke ckt jet in the bottom of each float bowl, that is a common one to miss as well. The pic below is just for reverance to show the Enrichening tube for the choke ckt.
carbs_floatbowl_choke by Tim Brown, on Flickr

 

Hey thanks for the welcome and the tips! Ill have to pull the carb rack back out and give those a look. Weather is finally getting nice enough that i can ride more than once a week so i want to get the thing sorted. Ill report back with my findings when i get around to it.