idle question

[montana.man]

bike seems to work fine pretty much all the time but when it gets warmed up and i rev it it goes up fine but around 2 thousand and down it seems aliitle slow idling down. was wondering wut it might be. i was also wondering wut the tubes that come from the tank are they are t tubes that go to carb three and four and carb one and two. it goes inbtween each carb, if these are loose could they cause a vacuum leak like im describing by the way its a 2005 suzuki katana. and also could it have something to do with the throttle position sensor or wutever that gadget is on the right side of carb number 4 any help would be appreciated

[gulfwardoc]

bike seems to work fine pretty much all the time but when it gets warmed up and i rev it it goes up fine but around 2 thousand and down it seems aliitle slow idling down. was wondering wut it might be. i was also wondering wut the tubes that come from the tank are they are t tubes that go to carb three and four and carb one and two. it goes inbtween each carb, if these are loose could they cause a vacuum leak like im describing by the way its a 2005 suzuki katana. and also could it have something to do with the throttle position sensor or wutever that gadget is on the right side of carb number 4 any help would be appreciated

When you say slow Idling down do you mean when you rev it up and let go of the throttle it takes a minute for it to retun to idle?

[KAT TOY]

the hoses are vents/overflows. you might try and adjust the idle mixture screws to richen your idle. i had to install a FP jet kit to fix my post 750. man what a difference. i also sealed the intake boots to the airbox.

[edc]

montana.man. I think I have the same problem as gulfwardoc describes it.

Idle mixture screws are set to 1,200rpm (when the bike is warm). After engine runs for about an hour on a hot day, when I stop at a light an intersection, it stays stuck at high idle around 2,000-2,500 rpm. Sometimes, blipping the throttle will work, and it will come back down to 1,200 rpm quickly. Other times, I have to wait more than a minute.

Anybody here know the cause?

[kevin2502000]

montana.man. I think I have the same problem as gulfwardoc describes it.

Idle mixture screws are set to 1,200rpm (when the bike is warm). After engine runs for about an hour on a hot day, when I stop at a light an intersection, it stays stuck at high idle around 2,000-2,500 rpm. Sometimes, blipping the throttle will work, and it will come back down to 1,200 rpm quickly. Other times, I have to wait more than a minute.

Anybody here know the cause?

Vacuum leak.

[jetta90]

Make sure you don't have a vacuum leak somewhere.......

[gulfwardoc]

Vacuum leak.

That would explain my part throttle hesitation as well.
anybody know off hand what size the Vacuum lines are? and the size of the Caps on the carbs? that way i can just go grab all new lines

[edc]

Thanks for the tip guys! Will go and see check my vacuum line.

[Wild-Bill]

Odds are it's not a vacuum line. It's an air leak from one of the boots or it may just be that the bike's gotten warm enough that the stock (slightly lean) setting on the A/F screws isn't quite rich enough. Either way, the cure involves pulling the carbs. Yank them out of there, drill out the EPA plugs and back the A/F screws out to about 2.25 turns. Put the airbox back on the carbs before re-installing them and make sure the boots aren't loose on the airbox.

[edc]

after checking the vacuum line and joints, they seem to be in pretty good shape and no leaks. same goes for the boots.

Wild-bill, you may be right about A/F getting too lean when bike gets hot. My idle hanging is when the engine becomes real hot especially in summer. Here in Manila its always in the 90's and 80-90% humidity.

I Brought the bike here in '03 never had a problem with idle hanging at 2k until about '09 when the Philippines made ethanol-blended-gas mandatory (minimum of 5% for all gas, with E10 replacing regular unleaded). Octane numbers here are different from the US. Here's its probably RON only with 93 (88 in the US) being the lowest available, while 95 to 100 for the premium gas. When i was in the US from 97 to 03, gas I used in the NE was just unleaded (not ethanol blended yet) and just the usual MBTE additives to improve emissions. I don't know if ethanol-blended gas is now popular there as well. (Haven't been back since).

Since I never had this problem with purely unleaded gas before, I'm gonna try not using E10 for the next two tankfulls and go for the more expensive gas with lesser/no ethanol in the meantime to confirm the lean theory.

If it goes away, then lean it is and the EPA covers will come off, if I decide to stick to E10 fuel... Read in some of the posts that leaning is causing idle to hang (and they have other engine issues but mostly due to clogged jets, with some saying ethanol causes gelling). Mine runs fine and never dies on me, although knock on wood I hope this is not the first symptom of this. That's why I'm thinking of using a premium high octane, high detergent and almost no ethanol fuel (if I kind find any first--I'll try techron) to counter this problem.

Wonder what kind of gas the other people here experiencing same idle problem... and what kind they were using before the problem occured, since I'm assuming they probably didn't change the A/F ratio.