Sluggish vacuum piston in carb

[KAWoodworth]

Would anyone have any ideas why the vacuum piston would be sluggish. I put a new spring on and a new diaphragm and thoroughly cleaned everything. I put new needle valves and seats in and now one carb's vacuum piston will not snap back quickly like the other 3. Also I noticed that the carb bowl drain screws were about an 8th of an inch out, So I tightened them. Put the carbs back on air boxes and tank. When I started it up gas was just dripping like crazy out of the bowl drain. I would think turning the screws all the way in would keep the bowl from draining. None of the other 3 leaked just the one with the sluggish vacuum piston and I tightened all the drain screws.

 

Tanks

[CaseyJ955]

Make sure the little white collar on the needle is seated, that tiny white finger slips into the hole. Also make sure all those peices are spotlessly clean. A bent needle can cause drag if it drags against the emulsion tube. Even making that plastic keeper screw that holds the needle assembly to the bottom of the slide to tight can cause drag. They need be only barely snug. Ill bet some playing around with that helps. Im assuming the needles are straight and the slides were clocked as they wre removed. Try the slide in the carb w/o the needle installed and see if it suddenly moves freely.

Edited August 13, 2018 by CaseyJ955

[Marcarl]

On the drain thing. There are drain tubes and overflow tubes. The drain tubes come out the side of the crab and the overflow tubes come out under the bike. The slide would really have nothing to do with overflowing fuel, although fuel in-between the slide and bore could possibly hang up the slide somewhat.

On the slide not sliding, check that slide real close, it might be cracked at the open side right close to the rings that hold the diaphragm. A crack could easily be missed. If it's cracked it will hang up.

[Patch]

Would anyone have any ideas why the vacuum piston would be sluggish. I put a new spring on and a new diaphragm and thoroughly cleaned everything. I put new needle valves and seats in and now one carb's vacuum piston will not snap back quickly like the other 3. Also I noticed that the carb bowl drain screws were about an 8th of an inch out, So I tightened them. Put the carbs back on air boxes and tank. When I started it up gas was just dripping like crazy out of the bowl drain. I would think turning the screws all the way in would keep the bowl from draining. None of the other 3 leaked just the one with the sluggish vacuum piston and I tightened all the drain screws.

 

Tanks

 

This is not a good practice to change just one spring!

It would appear that you likely have a slide issue, well that would be what should be addressed first. Changing one spring only/ can and will likely effect slide pressure; this in turn will effect power in the mid range first, if so this effects WOT (weather or not you tend to use it) because of the delay.

 

I assume your slide was at some point getting stuck open?