related to high rpms on cruze

[jazzrat2000]

Hi, this is an XS750 question, hope you don't mind! my bike also has a problem winding down from high rpms... the last time I rode it it was idling at 4500rpm (!!!) by the time I got home, I shut it down at that speed... when I restarted after it cooled (the next day) it idled at about 2000, and would come down very slowly (2-3 seconds) from a 3500-400 rev with the throttle. the throttle grip springs to stop quickly, and as far as I can see there is no outwardly visible sticking all the way the the carbs themselves... is my next step to take off the airbox and see what I can see inside? Keep in mind, I am barely able to tell which end of the screwdriver is the working one...

[Dragonrider]

I'd start by checking for vacuum leaks. . . . bad/split/missing lines/caps. Then look for leaks around the carb-to-engine boots . . . this seems likely as it seems worse when hot...you can tell if they are leaking very easily by spraying carb cleaner on/around them while the engine is running (it will change rpm/tone if there are leaks). Some also use propane from a small torch (unlit of course) to test.

Also, not sure about the 750, but is the vacuum advance hooked up right? (to a carb, NOT the boot to the engine) and is the advance mechanism free to travel/not sticky? Should be under the left engine cover...but maybe a 750 guy will chime in there....

[jazzrat2000]

I'll try the carb cleaner test tomorrow! thanks!

[MAXIMAN]

Keep in mind, I am barely able to tell which end of the screwdriver is the working one...

The pitfalls of musicianship...

I too am a musician....but I started with a wrench long before I did a guitar. Sad thing is after 30+ years I am pathetically wretched with either.

Another thing that might cause this is a sticky throttle cable.

[jazzrat2000]

it seems to go all the way back to the stop quickly when I release it.. but just in case, can you lube them somehow, or do you have to replace them?

[TopCatGr58]

Hey Doc Jazz,

They make special lubricating devices for cables, but you may be able to just pull it off, and pull the cable far to one end, and then squirt some spray lube on and into it. The special device sorta makes a seal, so that it allows the lube to be pushed into the cable....it's a tight fit between the cable and sheath!
T.C.

[jazzrat2000]

I am not understanding... if I look at where the cable connects to the carbs, and if it snaps back right away to its stop when I release the throttle, and the engine is still revving, doesn't that mean the cable isn't the problem? Please excuse my naivete... as another Doc once (almost) said: "Dammit, Jim, I'm a musician, not a mechanic!"

[TopCatGr58]

Hey Doc Jazz,

Your understanding correctly! However, where is the idle screw set at? If the throttle plate comes to a quick stop, but the idle screw is still holding the plate and all 3 butterflies slightly open, it's like you're still twisting the throttle, and it will rev!! So...look at the lever on the carbs that is turned when you turn the throttle, and you will see where it comes to a stop, and what it's stopping against, should be a screw that you can turn to allow it to stop further along the rotation. When the engine warms up, it leans out a bit, and that can also cause the idle to go higher, but like DragonRider(Dan Meyer) said, check for vacuum leaks, hoses as well as the intake manifolds, vacuum caps on the synch ports of the intakes, etc.!
T.C.

[jazzrat2000]

Thanjks, BTW this is the bike I am talking about!

C:\Documents and Settings\Administrator\Desktop\xs750004.jpg


Hope it works, I never tried to put in a pic before!)

[jazzrat2000]

Oh well, just like my mech work, it didn't work...

[don07tncav]

You have to upload to a photo hosting site then link the photo from here.