[MechaTomato]

I have finally found out the problem with my one carb, I think. I has to do with the circular plate that's connected to the throttle shaft in the carb.
On the left carb (the good carb) in idle position, only 1 of the two holes small offset holes are showing, and there seems to be no noticeable gaps around the disk.
On the right carb, (the bad carb), in its lowest position, both holes are showing, with the second one being partially shown. There is also a noticeable gap around the disk on the top right portion of it.

So after taking the disk out of the shaft, I can see that it kind of warped/bent (also, I did have it in the right way, with the beveled edges facing the correct ways).
So has anyone else have this problem before? Whats the safest way to bend it back to being straight, if possible? Also, the carbs are the 723b, and I found a throttle shaft assembly on ebay from a 723a carb. Would those be compatible being a and b?

 

[J-T]

Thought I had an idea until you mentioned the carb model. What bike are you working on?

 

[MechaTomato]

Thought I had an idea until you mentioned the carb model. What bike are you working on?

Oh sorry forgot to add that in there. Its a 74 cb450 with 723b carbs

 

[J-T]

OK, moved to DOHC carb section.

 

[Lefty]

I'd think with some scraps of wood and a flat referance surface you'd be able to get I flat enough with some hammer tapping.

 

[WintrSol]

I'd think with some scraps of wood and a flat referance surface you'd be able to get I flat enough with some hammer tapping.

The question is, 'how flat is flat enough?'. In my experience, you can't un-bend metal as hard as the brass throttle plates, so even if I could satisfy myself that it is flat enough, I would be looking for a replacement that doesn't cost more than gold.

 

[MechaTomato]

The question is, 'how flat is flat enough?'. In my experience, you can't un-bend metal as hard as the brass throttle plates, so even if I could satisfy myself that it is flat enough, I would be looking for a replacement that doesn't cost more than gold.

I'm going to try to unbend it but I think buying a replacement is the best option. I found a throttle shaft assembly for $25 that was taken off a 723A carb, so I'm not sure if the throttle plate will work with the 723b carbs, and if the plate is any different from the one that will remain on the left carb.

 

[66Sprint]

I'm afraid I can't answer this question for you.....
Back in the day, there were some carb parts you could buy/get separately, and some which if damaged required replacing the entire carb.....
So, I've never had to swap any butterfly plates, and cannot verify possible correct fitment......

 

[MechaTomato]

I tried bending the plate back, and got it fairly close to straight, but still not creating the seal like the other one. I also swapped the plates from each carb to make sure it wasn't the shaft or anything else.
Here are some pictures

one side


the other side


Both of these carbs are fully released (idle screw is having no effect, they're at full close). The one has half of the first hole visible, the other one has half of the second hole visible. What does the carb normally look like when its set up for idle? Is this close enough to it?

 

[WintrSol]

With that much difference, you may have trouble dialing it in. This drawing shows how it is supposed to work, with (a) at idle, and (b) just above idle:

 

[pattyandrick]

Be sure to stake the screws so they can't come out and damage the engine.

Sent from my SM-J320V using Tapatalk

 

[MechaTomato]

Just an update, Bending the old throttle plate wasn't good enough to get it straight, so I ordered the replacement from Ebay, which worked perfectly. The swapped side now runs more consistently at idle, but the whole bike runs rich now so I think that's to do with the uni foam air filters.