Super Jet brand new carbs with throttle/butterfly binding up

[Pablo]

I'm gonna give Art a call on Monday, but thought I'd ask and see if anyone's run into this before. I just installed my new carbs this past Wednesday and ran them maybe 10 minutes to see how the jetting was. Hadn't run them since then and fired up fine today. Rode to the beach and felt the throttle sticking. I rerouted the throttle cable thinking that was it. Nope.

It looks as thought the butterfly might be binding/rubbing on the inside of the carb body. Initially it looked as though the linkage was too thick and was rubbing, but not that either. It's only in the front carb with the spring. The butterfly (or whatever is getting stuck) is catching enough so that the spring isn't strong enough for the carb to return to idle. It gets stuck wide open and slowly returns to idle via engine vibration. The second carb is smooth as silk. It's only in the first carb. Occasionally it will loosen up and not catch. I tried gently tapping both sides of the arm that hold the butterfly, from the outside hoping it would alleviate some of the binding against the carb barrell, but no help there either. I've shot it down with lube and no changes with that.
Most likely I'll ship them off and have the master give them a once over to diagnose and fix, but if you've run into this lemme hear what fixed it.

 

[Cannibal]

Any chance your coupler is putting a load on the carbs?

 

[madscientist]

twist the spring one more rotation and re-install the cable pull.


i had this problem before and simply re-indexed the spring for more tension

 

[Pablo]

The coupler maybe causing a load on the butterfly shafts. When I pulled the carbs today I got them to work flawless prior to reinsertion. After reinstall they were right back to where they were. Sticking and real slow to return. I'd like to index the spring for more tension, but that's not fixing the problem with the primary carb binding. I don't really know for sure that it's the butterfly or the shaft is maligned. They've been babied really. I gently installed them initially and was gentle with them today. I can't imagine anything's been tweaked by me, but it's odd that they worked fine on first install and today they're all sorts of trouble.

Any chance your coupler is putting a load on the carbs?

 

[Pablo]

i took the primary carbs' throttle wheel/spring/plastic bushing off as well as nylon/metal washer and c clip from opposite side. With all that removed the butterfly operates smoothly. I applied a small amt. of anti-seize grease to all washers and butterfly shaft. once everything was back on it would still occasionally "bind up" and be difficult to rotate. It appears to be some binding between the spring and the plastic bushing. I was unable to get another full rotation with the spring to increase the tension. I lubed the bushing real well both on the shaft and between it and the spring. This made a drastic improvement nearly fixed. It's prolly 85% from perfect. Can't think of why it would be binding here???
Anyone think silicone based lube or graphite would be any better for this type of application? I tried WD40 earlier today and it didn't really make a diff.

 

[OCD Solutions]

I had a set of 38's do the same thing. They would be flawless on the bench but bind up after they were snugged down on the manifold. They had come with a series of spacers and flat washers that I did not fully understand but it was for shimming the coupler. I had to pull the coupler and adjust the width between the carbs to keep it from sideloading the butterfly.

I like a light throttle pull so winding the spring extra makes for much too heavy pull for my taste.

 

[SUPERTUNE]

Gregg,
Loosen the phillip screws that hold the throttle plate, only a 1/4-3/8 turn, now gently tap the ends back and forth, and find center where it's not binding, and re-tighten screws.
Chuck