Author Topic: 'idling' at 10,000 rpm (Read 2840 times)

El Dopa · « **on:** March 16, 2007, 04:10:50 AM »

While the board is up....

Got the carbs rebuilt by a professional workshop. when I took them off, a couple of the parts were knackered (jets, rubbers), so I let the professionals handle it.

They only rebuilt the carbs, as they were already off the bike. I put them back on today.

Started the engine, and it fires, but won't drop below 10,000 rpm - idles at 10,000.

Slides look OK, butterfly valves are opening and closing when I twist the throttle (and seem to be fully closing), throttle cable isn't jammed, and the rotating mechanism seems to be freely moving across the full range of movement. And it isn't the idle screw.

So, does anyone have any ideas?

gsxr400 racer · « **Reply #1 on:** March 16, 2007, 08:01:59 AM »

Take the air box off stick your finger in the slide and lift it up look at the butterfly on the other side is closed if not add some free play to your throttle cable with the adjusters or you have a major air leak but 10 grand rpm is exsesive.

Red01 · « **Reply #2 on:** March 16, 2007, 10:12:59 AM »

Quote from: "gsxr400 racer"

but 10 grand rpm is exsesive.

A slight understatement.

erik · « **Reply #3 on:** March 16, 2007, 10:24:45 AM »

have you made sure the choke isn't on at all? if the cable's tight or improperly routed, it might be opening the choke even with the choke lever in the closed position.

El Dopa · « **Reply #4 on:** March 16, 2007, 07:50:22 PM »

The butterfly valves are closed when I lift the slide - fully closed as far as I can tell (there doesn't appear to be any gap at the edges).

They rotate freely from fully open to fully closed when I twist the throttle.

Choke appears to be fully closed. I checked the cable and the slide, and it looks fully closed. There's an L-shaped piece of rod that acts as a stop. Looking at that, the choke is at least 3/4 closed, and judging by the dirt, as closed as it will go.

Idle screw fully out as well. The only query there is that the little stop/flange that the end of the idle screw touches stops about 2-3mm short of the hole the idle screw protrudes through - the ide screw neds to stick out 2-3mm before it starts to work. Is this normal?

So probably an airleak, but darned if I know where. Everything was fully in place and tightened up.

gsxr400 racer · « **Reply #5 on:** March 16, 2007, 08:00:06 PM »

air leaks would be at your inytake boots vacume hose and carb caps tops so as soon as you fire it up it goes to 10 grand? no that is not normal for the idle screw to be all the way out should stick up about a 1/8th of a inch whats your fuel screws set at?
ive had this happen on a few bikes where the carb sync was so out of wack that i couldnt even sync them i had to manually sync them then try all over again .

Bartjan · « **Reply #6 on:** March 19, 2007, 06:20:21 PM »

sounds like an air leak.

you can test for a air leak by spraying brake cleaner (or start spray) around the carbs while the bike is idling. if the rpm goes up more youre spraying at the leak.

note: dont spray on the airfilter, because the rpm will also rise

PitterB4 · « **Reply #7 on:** March 19, 2007, 09:34:41 PM »

Quote from: "gsxr400 racer"

ive had this happen on a few bikes where the carb sync was so out of wack that i couldnt even sync them i had to manually sync them then try all over again .

I think you sold those carbs to me.

gsxr400 racer · « **Reply #8 on:** March 19, 2007, 11:53:22 PM »

lol