Hi Guys,
Let me start by saying I bought an ALL original 1973 CT3 175. 2600 miles did not run. It's a beauty to look at. I figured if I couldn't get it to run I could either part it out or replace the motor.
The only thing missing is the tool kit.
Replaced all seals and found out why it didn't run and fixed that issue. The original carb was froze up. I bought one from fleabay that is a Mikuni which I was assured worked just needed cleaning. (I took advice from this forum). Cleaned it up only to find a huge fuel leak. In front of the banjo blot in the float chamber there seems to be a brass fitting of some kind. Just a hole. I looked at my other 2, 175's and there is a brass plug of some sort.

Does anyone know what should be there and can I find it somewhere on line?

I put a new carb on (from fleabay). She started right up. It runs great at idle but bogs when given throttle. Too lean?

I would like to put the old carb back in if it can be fixed because it fits the original air cleaner better.
Tsmitty

 

That brass "plug" is actually the main jet, although I don't think that it's absence would cause a fuel leak. It could be that the tang on your float needs adjusting.

       

       imgur.com/a/GNa0cDf

Gr8 here's a pic if I did this right.

You probably did do it right. HOWEVER, Imgur have spat their dummy out and no longer operate in the UK, therefore I can't see your photo(s)! 

Dang. It's shows the open hole and fuel comes out of it.

This is about the third or fourth time this same question has come up on the CT3 carb.  

Some have blocked it with a short screw but originally had a brass ball peened into the hole.  

yamaha-enduros.com/index.php/forums/1972...tor-questions#104406

Thanks Mark.

It kinda looks like some of the CT3 carb bowls had a manufacturing defect where the ball falls out.  

Such an unusual problem that I've only seen come up on that model.  And most Mikuni carbs have a few of those brass balls in various places to block a drill passage. 

Thanks again Mark Very helpful. I ordered a 4mm brass ball. (100) $6. While I have you, the motor sounds like there is a little man in there banging on the case with a hammer when I accelerate. Going to remove the motor today and check the bearings. Will I need a crankcase splitter?
Tsmity