CLICKING NOISE KEIHIN CARB

Hi i have a keihin carb on my KTM 250SX and at the first smallest twist of the throttle (maybe 2mm) there is a small click noise coming from the carby, 

The spring looks good the small white collar at the end of the spring is sitting correct in the groove, everything is in place correctly

I tried flipping the spring and still did it

The throttle is smooth all the way to WOT no problems just that initial 2 mm of throttle twist there is a click

I'm thinking just leave it or?

Edited by throttle violence

Check your slide for any small knicks. Check your needle for the same, and make sure it's not bent. Is there any resistance in the throttle right before it clicks?

Edited by Cartoscro

My sons 85 was doing the same thing, too much slack in the cable, and the tang on the slide end of the cable was popping in and out.  I adjusted his cable and the noise went away.

19 minutes ago, Cartoscro said:

Check your slide for any small knicks. Check your needle for the same, and make sure it's not bent. Is there any resistance in the throttle right before it clicks?

No knicks or bent needle no resistance, it clicks at first smallest twist of the throttle about 2 mil definitely coming from the slide area 

And...FWIW, I wouldn't leave it.  If the cable pops out of the slide you might end up with cruise control at an inopportune time.

I agree with checking your cable slack. Even if that's not the cause of the click. You should have just enough slack in the throttle that when you roll off you can hear the slide hit bottom and that's all.

Any excess slack in the cable will show slop at the cable ends where they mount in the ferrules. Then when you twist the throttle, slack is taken up and the cable end bottoms in the ferrule before the cable actually starts to lift the slide. That could be making noise.

You've tried swapping the spring end for end. Try just rotating it 90* to change the position of the coils.

13 hours ago, Trailryder42 said:

I agree with checking your cable slack. Even if that's not the cause of the click. You should have just enough slack in the throttle that when you roll off you can hear the slide hit bottom and that's all.

Any excess slack in the cable will show slop at the cable ends where they mount in the ferrules. Then when you twist the throttle, slack is taken up and the cable end bottoms in the ferrule before the cable actually starts to lift the slide. That could be making noise.

You've tried swapping the spring end for end. Try just rotating it 90* to change the position of the coils.

Yes i tried the rotation but still the same i thinks it's just the initial first pull on the slide (2 mil) that's making the click just as you said the cable bottoms in the ferrule before the cable actually start to lift the slide , though i have got 2-3 mil throttle play which is perfect i think so i cant adjust anymore, i probably wont worry about it.

Edited by throttle violence

This is redundant, but the same thing happened to me when fiddling with the needle position. I had to turn/twist the spring to make it go away. There shouldn't really be a "sweet spot", but at least on mine, apparently there is...

have you checked for any frayed wires? check around the nipple in the throttle housing. it could be the cable starting to break. 

unhook the cable from the carb slide and pull the throttle . this should tell you if it carb or cable related

inspect!!!

and be sure the top end of the springs coil is in the cap properly not any kind of off center...

 

Edited by THUMPERRRR

For a few years I've had a click from my slide spring at about 1/3 throttle open on my PWK38 on my YZ. It's the coils over-riding on one side. The fix has always been to rotate it and retry. But I must rotate the spring in the direction to tighten the coil. Sometimes it takes a few goes to get it.  Finally I decided it was a pain when making quick needle changes for jetting experiments, so I've bought a new Keihin spring and will install that the next time I need to open it up. Fingers crossed it goes away. Def my spring. Once adjusted right it stays smooth.

1 hour ago, numroe said:

For a few years I've had a click from my slide spring at about 1/3 throttle open on my PWK38 on my YZ. It's the coils over-riding on one side. The fix has always been to rotate it and retry. But I must rotate the spring in the direction to tighten the coil. Sometimes it takes a few goes to get it.  Finally I decided it was a pain when making quick needle changes for jetting experiments, so I've bought a new Keihin spring and will install that the next time I need to open it up. Fingers crossed it goes away. Def my spring. Once adjusted right it stays smooth.

Yeah definitely the spring mine was also at 3/4 throttle clicking and i spun it around a few goes and it stopped

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