Butterflies not sealing - showing light sliver

After a bunch of head scratching and playing with the parts, I have the carbs reassembled as a devote member of the Church of Clean.

However, when I look at the butterfly valves themselves, there is a little sliver of light coming through at the bottoms. How can I solve this issue?

 

It is best to have the screws loose when you install the butterflies. Then get them centered and shine your light from behind and make sure they are sealed up as best as possible. The engine should sync up fine when you get to that point.

MN

 

That's assuming you did get the butterflies oriented correctly when you reinstalled them.

Mikuni butterflies aren't "straight" on the edges, they're angled slightly to better fit the bores. If you accidentally got one or more "flipped over" then it can cause the issue as well.

If you're 100% sure they went back in the same way they came out, then the above advice applies. The only Mikuni I've ever seen seal PERFECTLY is the brand new NOS one I have. All 16 of my other ones (2 bikes' and 2 spare racks) show a slight "light leak" to one degree or another; but none of them are brand new. (And they all work fine.)

 

I have them oriented the correct way. I think the edge of one might be slightly chewed from my hemostat during removal. How important is it that they be tightly sealing (or at least consistent)?

 

If one got chewed, pull it back out and gently smooth off the "chewage."

The tighter the better; do your utmost.

 

I gotta ask......

The idle stop screw is supposed to open them just a bit to allow fuel/air for idle. If the screw hasn't been backed off they'll never close.

 

You are correct sir - the idle stop screw does effect these types of things, but it's backed out enough to not be contacting the throttle cable quadrant on cylinder 3, but thanks for the reminder.

 

Right. But if the individual screws aren't anywhere near sync'ed, one of THEM might be holding it's butterfly open.

Apply Carls' advice not only to #3 and the main screw; but ensure the others are allowing full closure as well. Those pesky springs can fool you...

 

This is also true, but i've bench synced them with the paper-clip method - Im pretty certain it's just the chewed up edge. I filed it just a bit to get rid of a spur on the edge, and it sits better, but I'll just have to proceed with it as is - fortunately a relatively easy part to get to if I find a parts rack.

Thanks for all the ideas guys 8)