Falling RPM's while idling...

[femmekat]

I was hoping to get at least a couple weeks of riding in before having to post on here with more questions, but it's not meant to be...

1991 Katana 600, which I have owned for several weeks now. Was running great, and now suddenly it won't maintain RPM's at idle. This literally happened overnight, and was not a gradual process... The only way I can keep it running at idle, either while warming up, or at a traffic light, is to have the choke on. By fussing with the choke, I can get it to maintain high enough RPM"s to keep running, but it sounds rough, kind of an up and down type noise. If I turn off the choke, the RPM's start dropping so low the bike just shuts off. Stop and go traffic was a blast today with the bike running like this... I bought some fuel additive, but it has not helped yet. It has been suggested to me that it may be the carbs, but wouldn't that be a gradual process? Not an overnight change?

[kevin2502000]

It probably is the carbs nd yes they can change anytime depending if a chunk of debris dislodged or moved somewhere else. Idling problems are usually dirty carbs.

[Kreylyn]

Running fine, running fine, running fine... then bam, no idle?...

Was the tank low on gas when this started, or switched to reserve by chance?

Have you tanken a flash light and inspected inside the tank for rust/dirt/water? Has it been flushed as far as you know since you purchased it?

Only 3 things on carbs control the idle. Pilot jets, floats, and air/fuel mixture screws. The only 1 that would normally change suddently on it's own would be the pilot jets getting clogged up.

Krey

[md86]

Turn the idle adjuster up .

[DumbLuck]

check your sync port caps, and other vacuum connections, one may have popped loose. cleaning the carbs is not the end of the world, nor that tough. If things go smoothly you're only talkin less than a day of the skoot being down.

[femmekat]

Yep...running fine, fine, fine, then bam, no idle... The tank was lowish...but above the red (only took 3 gallons when I filled it today....) when this happened...

Have not checked the tank itself....
Will need to figure out how/where? to adjust the idle...and where the heck the sync port caps are.....

[Kreylyn]

Yep...running fine, fine, fine, then bam, no idle... The tank was lowish...but above the red (only took 3 gallons when I filled it today....) when this happened...

Have not checked the tank itself....
Will need to figure out how/where? to adjust the idle...and where the heck the sync port caps are.....

3 gallons is just before I hit reserve normally, so it would be low enough to pick up trash if you have alot in the tank.

I would check it, possibly may need to flush and clean the tank. They do collect water and other stuff in the bottom over time.

"sync ports" would be small nipples on the top of the carbs, on the edge of the "black caps". There are 4, and each one should have a rubber "cap" to prevent it from leaking vacuum.

There was another thread where someone posted the "idle" adjustment pic with the location highlighted on a post kat, but it's in the same location for the pre...

Look on the left side (as sitting on it), large opening in the main fairing, just under the carb bodies, should be a knob right near where the frame runs down. 1/4 turns to adjust... but...

If it was running fine, I don't think that would be the issue...

Krey

[kidblooper]

I'm thinking bad gas run a bottle of heet through it. sometimes its the simple stuff and not worth taking everything apart. I'd run the whole tank out or empty it out, As well as checking for vacum leeks as Dumbluck stated, if you still have a problem.. yep bust them carbs apart clean up good and pop them back in.. not then end of the world