We call it a "jet", but of all the bowls I've seen (which includes some new ones) there is no brass or brass "jet" in that hole. You could drill it out, but I'm sure the hole is a very specific size.

It might be best to add some JB Weld (a common hardware store filler epoxy) over the brass that's there now, and simply drill a brand new hole in a new location. The brass may have wallowed out the existing hole and any attempt to remove it might leave a gaping hole that's way too large.

The replacement bowl I had to buy was $50 plus shipping from Bing. So you can do a lot of repair work for that much.

You could drill it out, but I'm sure the hole is a very specific size.

Since no one else seems to want to dive in.... a #48 drill bit (0.076") drills the correct size hole. These are available individually at any good hardware or hobby store.

For long time all I saw was screwed in brass 'jets'. Then someone told me they had a drilled hole and I immediately felt inadequate.

The hole is the refill passage to the cold start bowl. The cold start system has an automatic progression. It starts out rich and then leans itself out. if you are cranking the bike and it doesn't catch pretty quick pause to let the starter cool and the cold start bowl refill. There is another tiny hole hidden halfway up the cold start pick up tube. It's the bubbler hole.

You do not have to get air through it. Fill the bowl with alcohol and if the cold start bowl fills through the hole you are good. If it does not try reaming the hole with a piece of stiff music wire. The hole size is not critical. if it is too big the cold start will run rich longer ; too small and it will lean out quicker. But it is a pretty crude system.

I cannot think of any sort of brass that could have collapsed. Those screwed in jets were beefy. They were also a never-remove-this item. But you could have a brass shaving off some other jet wedged in there.

Worst case someone already tried to drill it and broke the tip of the drill off. Just drill a new hole somewhere, anywhere, any angle such that the bowl will fill from somewhere near the bottom of the main bowl. I think Wobbly gave the drill size for the drilled hole.

Reflecting on this a bit more it occurs to me it might have been a bowl with a screwed in brass jet. Check the other side. Then someone tried to unscrew the jet and sheared the head off. This would give something like you describe.

Reflecting on this a bit more it occurs to me it might have been a bowl with a screwed in brass jet. Check the other side. Then someone tried to unscrew the jet and sheared the head off. This would give something like you describe.

Regardless. You have a twin carb motorcycle. Both carbs need to be identical twins in order to run correctly. Either both carbs require the jets in the float bowl or neither carb requires the jet in the float bowl. Which is it and what's the other float bowl have ??

i wrote my post poorly. When I said "check the other side" I meant look for a brass jet on that side which might indicate that there was one on the troublesome side. Regardless the troublesome side might have been replaced with an older brass jet bowl.

Both sides need a jet and they should be halfway matched. My RS does not fire on both sides at once, one side always leads by a couple hits. Always been that way. A long as it fires I'm happy.

All good, but Andrew needs to follow up with more info.