Hot bike doesn't run

[maximilian]

Hi all,
I've got a 81gs450l 16000 miles I've done the carbs(soak orings etc) adjusted valves and chain tensioner someone screwed with,and it runs great. Until it's good and warm then the idle sticks at @3000 rpm and if u ease the clutch out it will draw the rpms down until it idles but then is very doggy on the throttle until 2500 and if u shut it off hot it won't start again until it's completely cool. I'm thinking it could be the slides sticking when they get hot on the low vacume side but they seemed smooth when it was apart. Also anyone know @ what vacume pressure I should be reading at a certain rpm??

 

[Nessism]

Have you replace the intake boot O-rings?

 

[maximilian]

Have you replace the intake boot O-rings?

Yes that was the FIRST thing I did when I was diagnosing this bike.

 

[tom203]

Sticking slides won't prevent startup... So you replaced boot o-rings, how do boots themselves look? Clamps tight?

 

[Steve]

A hanging idle when warm suggests intake leaks. If you have changed the o-rings, how about the boots?

First, there is no such thing as "vacume pressure". Second, there is no set vacuum for any given situation, it is all dependent on your particular engine.

Have you synchronized the carbs? On your bike it's particularly easy, as you only have one adjustment to make between the two carbs.

Oh, your keyboard appears to have problems with the Y and O hanging up. They don't seem to work all the time.

.

 

[maximilian]

Sticking slides won't prevent startup... So you replaced boot o-rings, how do boots themselves look? Clamps tight?

The boots look brand new clamps are tight.Ive had carbs on and off 3 or 4 times now.stock air box,nice seals stock exhaust.it will come down from 3000 rpm and run wen hot, but i cant shut it off from an idle or it wont start till its cool. if i shut it off at 3000 rpm it starts right up, and its ALWAYS doggy from idle to 2000-2500 rpm.

 

[maximilian]

The idle doesnt really"hang" it gets stuck at 3000 rpm if you let the clutch out some and drag rpms down it drops to an idle. ive tried the carb clean wd 40 spray looking for vacume leaks to no avail.

 

[Steve]

Mixture screw settings?

.

 

[maximilian]

I started at 2 1/2 out, turning 1 turn either way doesnt affect the idle so i set them back to 2 1/2 out. brand new plugs are black with some tan near the tip of electrode.

 

[Nessism]

Changes on the backside of the carbs can cause lean running (and a hanging idle) too. Airbox mods, leaking airbox boots, missing/crappy air filter, etc, can all cause running issues. So can a dodgy vacuum sync job and a sticking mechanical advance unit. It seems that people don't lube the advance rotor and weights very often and rust can set it and make them stick.

BTW, spraying crap on the boots in search of an idle change is not a reliable way of finding vacuum leaks since this method only finds gross leaks, not smaller leaks such as the type what affect the idle.

 

[Gorminrider]

or just Maybe try turning the idle down when the bike is warm and go from there. These two cylinder bikes can take awhile to warm up especially where everything is not brand new in the idle and enriching circuit.. . There's a big finger nut for this at the carbs-look under you'll see it if you don't know what I mean.
plenty of stuff and links on Bass-cliffs site about CV carbs...

...also be sure to check your throttle cable is not tight or hung up somehow...Turning the handlebars side to side is a good check too.

 

[Buffalo Bill]

You haven't said anything about the airbox and exhaust, are those stock or removed-replaced?