Topic: carbs wont return to idle.

[themanxman]

Hello all.
I have a Z engined bike with PD51a carbs. The newly rebuilt engine will not return to idle without some assistance, ie let the clutch out a little in gear and it will come back down under load. It does go well at higher revs.
It has a fairly quiet 4 into 1 exhaust
cheap pod filters
115 main jet (also 92, 107.5, 110, 115, and 120)
return springs are strong
cables free
pilot jets have been out and are clean
new neoprene manifold rubbers (in blue, nice!)
ignition advance weights return nicely
needles are on the middle notch
fuel levels in the float bowls are at the joint/top, measured with clear tube
and the camchain clatters.
can anyone point me towards a solution ?
Cheers Pete.

[evanphi]

does the linkage snap back down completely without the cables attached?

let the clutch out a little in gear and it will come back down under load.

This is interesting. Does it stay down after this? Idle speed dropping with clutch resistance is normal (we've all stalled our bikes before!), but it would come right back up when you bring the clutch back in.

[themanxman]

Hello. yes it comes back and stays there, it will slowly return if left alone some of the time.

[themanxman]

Sliders seem to be working fine without cables.

[dusterdude]

If you fix it let me know,mine is doing the same thing,been thinking its the spark advancer hanging but im leaning away from that,ordered a new cable this am.see how that goes

[Muckinfuss]

make sure you haven't developed and air leak at the intake that's leaning out the idle.  with the engine running spray WD or some other silicone spray at the intake parts seams on the head side of the carbs, one seam at a time, and watch your exhaust for smoke.  No smoke, no leak.

[Deltarider]

make sure you haven't developed and air leak at the intake that's leaning out the idle.

This is the first (and simplest) test to do.

[themanxman]

Will try that in the morning. Thanks.

[dusterdude]

Good idea on the wd

[themanxman]

Hello again.
Sprayed WD 40 all over manifold area and it seemed to make no difference, did the same with Easy Start, same story, sprayed the Easy Start over the air filters and the engine stalls, flooding ? Anyway. I was checking around the clamps and giving them an extra tweek when i noticed that tightening one of them caused the revs to rise ! Culprit found. My nice blue neoprene manifold rubbers are to soft, the clamps are pinching them. So I dug out the originals which were horribly stiff and quite cracked, which is why I abandoned them without having tried them in the first place  and put them back on.......IT WORKS !

[Muckinfuss]

Absolutely the best, non-deforming, clamp tool ever made...........http://www.clamptitetools.net/       "regular hose clamps with the worm gear almost always deform the hose/tube/pipe  etc.       This thing is better, faster, cheaper.