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Discussion Starter · #1 · (Edited)
I bought my 73 CB350 a number of years ago and it had fuelling problems form the start. The engine ended up having oil starvation and blew itself up, and now I'm finally rebuilding everything. I had bought a spare set of carbs to use parts off if needed.

The problem is that the left side idle lever wont go metal-to-metal at all. The reason I bought the spare carbs is I thought the shaft might have been twisted, or even the casting somehow flawed. I swapped out the shafts & plates between the 2 carbs and still no metal-to-metal. I bought another set of shafts and same problem. Mixed and matched the 3 shafts, 3 plates, and 2 housings every which way (and plates flipped around) and I can't get the lever stopper to touch the housing. The left carb completely covers the low speed hole whereas the right side exposes about 50% of it at its fully closed positions (left throttle plate touching, right lever touching). When removing the left plate altogether to allow the shaft lever to touch the housing, You can clearly see that the left carb is at about a 15deg angle whereas the right is about horizontal.

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Discussion Starter · #4 ·
I tried all 3 every which way. Made sure that the angle of the edge matched the way it closed so it aligns with the bore
 

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The mounting holes on the shaft are slightly oversized so the butterfly can be moved to find Center.

Center it befor tightening

also tje butterfly goes in only one way with the beveled edge... did you properly orient the beveled edge?
 

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Here's a good image showing the plate to lever position. This is the same in all the configurations I tried.
outobie is right in my opinion. You have to rotate the shafts and 'slide' the plates about so they are self centered in bores. left / right as well as up / down.
If the plate edges are damaged they can be 'too wide' to fit properly. although in the picture it looks like there is only a gap off to side as throttle plate needs slight rotation ? (gap isn't at top or bottom but 7:00 o'clock) I've had it happen and it's a pain to correct sometimes,
The pilot discharge hole should be visible in front of throttle plate, the transition holes under plate edge may or may not be partially visible
You need to check all plates and shafts for burrs, I use a x10 loupe when I'm rebuilding carbs, (plus I've had to make a load of special tools to 'fix' various things on 350, 360 and 450 carbs)
The staked screws often cause some damage when removed which may be inside the plate slot in shaft. The shafts are chrome plated brass so pretty easy to 'tweak' on un-plated sections
 

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Discussion Starter · #8 ·
Sorry for the late reply. I made sure that the bevel aligns with the bores so that it becomes aligned as it closes. I did notice that some of the plates would stick on the sides of the bores, so I lightly filed them to break the edges and now the go in smooth. Plates are loose in all these test fits to make sure that they can find their own position. I'll try to clean the bolt holes in the plates a bit in case that's causing the issue, but even before I put the screws in, I can see that when the plates "find center" the holes are all clear and screws go in without catching. Both bores measure at 32mm.

Looking at this video where Common Motors does a bench synch,
, I see that it's actually correct to have the plate be the limiting factor in rotation and the lever shouldn't be touching the housing at full-closed position. So maybe it's my right carb that's causing the issue after all. However I tried multiple plates and positions (all beveled edge aligned with the bores), the multiple shafts I have and within both housings and in all configurations, I have the lever touching the housing.

Regardless, watching the video, I see that the starting point should be with the plates exposing the 2nd hole (is this the pilot discharge hole?). I can get both plates to this position using the method he outlines, so when I finally crank the engine over, I'll see if this starting point resolves it. During my rebuild, I found that the throttle cable was damaged, so that might be the solution for my previous fueling issues, and this may be a non-issue altogether.
 

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You use plates to initially set position but you need to use throttle stop screws to prevent plates and carb body getting damaged. (they will wear grooves in body it you use them instead of throttle stop screws)
 
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