High Idle after carb cleaning

Hey folks,

I know I've read about this before but I wanted to hear from you all before I go fooling around with plugs and such.

After totally disassembling and cleaning my carbs, the bike wants to idle VERY high- around 5000 rpm. I adjusted my throttle cable while I had the tank off, so I thought maybe I overdid it without realizing. I readjusted the cable and it helped a tiny bit, but doesn't seem to be the real issue.

Is this just a vacuum leak? Where are the likely places given the recent work? Everything was reassembled as before. None of the vacuum ports (at least the 4 on top) are plugged, but there is a hose running from #1 to #4 and #2 to #3.

Any ideas are appreciated.

1983 GPz 550

Did you center the idle control screw (the big knob) when you re-assembled the carbs? If not, it may be holding the slides up too high and have no adjustment travel left to lower them. Ed

650ed wrote: Did you center the idle control screw (the big knob) when you re-assembled the carbs? If not, it may be holding the slides up too high and have no adjustment travel left to lower them. Ed

I didn't actually remove the idle control knob when I took them apart. Can over loosening the knob cause it to fail?

Sounds like a classic vacuum leek. Start your bike and spray carb cleaner around the carb holders when the revs drop or it dies you have found your leek. How old are your carb holders? They dry out and pull away from the head and develop small cracks. Although it isn't recommended with new holders I always use type 2 gasket sealant when replacing them.

mangosteen wrote:

650ed wrote: Did you center the idle control screw (the big knob) when you re-assembled the carbs? If not, it may be holding the slides up too high and have no adjustment travel left to lower them. Ed

I didn't actually remove the idle control knob when I took them apart. Can over loosening the knob cause it to fail?

If the idle control screw is turned counterclockwise near the end of its travel, and if after that the height of the carb slides is set, the idle control screw will no longer be able to lower the slides to reduce the idle rpm. It will be able to increase the rpm by turning it clockwise, but since it is already turned about as far out as it can go it will have very little affect when trying to use it to reduce the rpm. Ed

Try bench syncing the carbs, your slides could be too high. Check each one.

Thanks for the input, all. I pulled them off again. Inspected the slides, butterfly valves, throttle cable assembly, etc. everything seemed to be in good order.

I put them back on, but this time used winbags to press them firmly towards the carb holders while tightening the clamps. Fired right up and idles and revs better than ever. I think the weight of the carb body itself made it sag a bit last time i tightened things back up, and there was a bit of an air leak. Fingers crossed it stays seated well!

I'd highly recommend winbags to anyone who is often shimming things or doesn't always have a second set of hands around the shop.

Thanks!

Joe