CV carbs are the great separator between mechanical people, you either get them or you don’t. Let’s start with some simple numbers. What main jets and pilots were in the carbs when you started and what have you upgraded to now? Have you followed the CV carb tuning procedure outlined by Factory Pro?

 

Off hand I don’t remember what is in there now. I’ll take a look on my next day off and update on that. The only one I know right now is the pilot is 45. Anything smaller and it ran lean sooner when I would blip the throttle. I ordered my carb kit from tjbc and followed his tuning guide. I’ll look into factory pro.

I will say, last year when it ran it seemed to be a dog down low. Until I hit somewhere around 2500 it had no power, then all of a sudden picks up and runs like I’d expect. Reminded me of VTEC in my old J30 accord actually.

 

Not to jump in and spoil Froth's party but have you checked the diaphrams.
It seems you have covered most other stuff, and was running jetted as is, if diaphrams have been checked, I'm sorry for the intrusion.
And know that it will never run as good as engineered/stock, with pipes and stacks
After much trial and error you will be content with "good enough for now".
jmo

 

Forgot to mention that one. Alright so I’m about to get ******* for a second. The diaphragms are cracked. Not like fully blown out ruined but a couple of small cracks. I ******* electrical taped it for testing purposes and am going to purchase new ones because I’m 100% aware tape isn’t the ideal way to handle that. But even after I did that, upon immediate fire it ran no different.
I would be very satisfied with “good enough”

Side note, where can I find diaphragms that aren’t $50 a piece? I’ve only found them on one site and eBay and shipping times were much further out than I want to wait for. Last time I looked was a couple weeks ago.

 

Forgot to mention that one. Alright so I’m about to get ******* for a second. The diaphragms are cracked. Not like fully blown out ruined but a couple of small cracks. I ******* electrical taped it for testing purposes and am going to purchase new ones because I’m 100% aware tape isn’t the ideal way to handle that. But even after I did that, upon immediate fire it ran no different.
I would be very satisfied with “good enough”

Side note, where can I find diaphragms that aren’t $50 a piece? I’ve only found them on one site and eBay and shipping times were much further out than I want to wait for. Last time I looked was a couple weeks ago.

I'm not sure how tape on a diaphram would workout, sounds sketchy to me, I'd come up with a better fix (new diaphrams from the link CSRoad posted $20ea.) before chasing any other perceived carb problem.
Good Luck
out,

 

From what you describe it makes me wonder if something's wrong with your choke system.

 

Actually, that’s a question I have. How does the choke work on these carbs? What I’m used to working with is theres, essentially, a second throttle plate that’s cable activated in front of the main throttle plate that is controlled by user input for acceleration.

What would I go looking for on the choke for proper function, and what am I looking for to go wrong?

The only other carb bike I’ve ever had, I bought freshly redone and the carbs were already tuned and sync’d so I never had to touch them. My carb experience is solely with Holleys and one Edelbrock Carter clone.

Oh! Forgot this earlier. There are 4 really small pin holes in front of the throttle plate on these carbs. With the bike off and carbs mounted on the bike, and with fuel shut off, fuel comes out of those holes and will fill the cylinder with fuel. I’ve even disconnected the fuel line from the T on the carbs and it’ll still drain out on both of the carbs. If I remove the carbs while this is happening it will immediately stop.

 

There is a clue for sure. The small holes are transition ports = when you open the throttle and the fuel can flow as the plate opens gradually. If fuel is up to flooding them, it is overflowing internally. I was going to say the float valve is probably not seating.
Or the float level is just off.

 

I have checked the floats to make sure they do actually float, which they do, and have adjusted them down to a much lower level just for kicks to see if it still happens and it indeed does.

I have also pulled the bowls and manually lifted the floats with a fuel line hooked up to check that fuel flow gets cut off and it does.

Where do the transition slots draw fuel from? The bowl obviously, but from which part?

 

I am pretty sure they get fuel from the pilot jet, low speed circuit- the idle circuit.
Are you setting the floats with the carb body at a 45 degree angle and the float just barely putting pressure on the spring? Book I looked at showed 7 MM.

 

Didn’t think to adjust them at an angle like they are while on the bike. I’ll go back and do that next, along with any suggestions anybody else can give between now and then. Only one thing at a time of course when I do.

 

Good info video=

 

Good diaphragms, good price.

JBM Industries Rubber Carburetor Boot Socket Holders & Diaphragms

JBM Industries rubber carburetor holder socket boots, flange intake sockets, vibration isolators, stainless steel exhaust springs, for Rotax 912, 582, 503, 447, 377, Zenoah & HKS engines. Yamaha 650 SX & TX Mikuni BS-38 & 34 CV carbs. Diaphragms & holders.

jbmindustries.com

 

definitely,fix the obvious problems, then see if the rest of them went away.

 

I'm not sure I could explain the chokes so you could understand it,
barely have a handle on it myself...other than Works/Doesn't Work...
But I know what it sounds like when it's struggling and to flip it on

 

The choke is actually and "enrichment" circuit. I tried to follow it once and it goes north, south, east, west , with passages and orifices all over . I never did get a handle on it.

 

I’m a bit similar to you, and I had a similar issue with carbs that I’d gone over a few times, AFTER a complete strip down and cleaning... How I fixed it, was I went to my original carb set (think the first ones were off my parts bike) that I’d cleaned and conditioned the same way, at the same time. So something is still wrong with that one set of carbs.

There’s a reason fuel injection is awesome...

 

Good to know the choke is actually enrichment. Makes sense, just hadn’t thought about it. I’ll check it out too, see if I find anything funny with it. Knowing that, I’m thinking it’s possible for something with the choke to be wrong and possibly causing my flooding issue. Still doesn’t explain why the fuel flow out of the pilot will full stop once the carbs are removed from the bike though.

I’d love fuel injection but I didn’t pay much for the bike so I was content with it being carb’d. Well, at least when it ran right!

 

I kept thinking about the choke too, but it will only work with the engine running to create a vacuum and air flow. If the fuel is running out of passages with the engine off, it has to filling too high in the bowls.
Think of the toilet bowl operation.
Same principle = the water comes in till the float hits a set limit and then shuts off the water flow valve.
If it fails the water keeps running over the stand pipe inside the tank and runs down into the bowl until you shut it off.

 

That’s been one of my stumbling points too. Just for kicks I adjusted the floats unreasonably low and still got the pilot bleeding issue. Again, I’ve verified the floats and everything are doing their job and shutting fuel off as they should. This is the part I’m really stuck on because it makes no sense to me at all.

 

Also, I want to thank everyone who has contributed here. I appreciate all of your input and now have new avenues to explore.

Tried getting on the Factory Pro site but every time I get a message saying the connection was lost. Have only tried on one device, will try again on another one later.

 

One more idea is that if the fuel pump has been changed to an car rated pump with 7 pounds pressure, it can push past the float valves. It is supposed to be only 2-3 pounds on these carbs.

 

Good Call
I use this a vac pump for replacing oem pumps, no electric connections/small/cheap.
It pumps all the time the motor is running/cranking without a bunch of condition switches to get power like an electric pump.
It's only querk is it can't be mount flat horizontally, the inlet port must be tipped up for gravity head pressure from the tank, so lower than the petcock too.
I angle them up about 20 degrees or so, figured this out when I bought a Yamaha Seca II and it had this vac pump stock/oem:

Amazon.com: Mikuni DF44-227 Genuine Single Fuel Pump : Automotive

Buy Mikuni DF44-227 Genuine Single Fuel Pump: Replacement Parts - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

READ the product description for other Mfg'er name/part number as some are clones, even with Mikuni pictured cast in the pump.
Still more unsolisited useless info,

 

At some point we hit the bowl a few times, which stopped fuel gushing out of the vent hose and butterfly valve shaft. But if left alone, it would eventually fill the intake throat with gas, so there is still a blockage somewhere.

 

I thought about fuel pressure too. So, mine was missing the pump or vacuum petcock or whatever it is. Just had a hose running from the tank to a filter, and filter to the carbs. Two things here though.

1. I ordered a fuel pressure regulator. One that goes from 1-4 lbs and adjusted it from its highest setting to its lowest and was still getting the issues I am now. There was zero change in anything at any point with it.

2. Because I kept having to pull the carbs to do everything, I just don’t even have the tank on anymore. I put about 3’ of fuel line on the carb with a filter in the middle and a funnel on the other end. I have a clear filter so I can see any crud that ends up in the filter, which works out here because if I let the line run dry the bike will idle up and run normal. If I put fuel back in it will immediately idle down from too much fuel again.

Gasoline is 6 pounds per gallon so there’s no way I have much fuel pressure in just that 3’ of line.

Now, I have at several stages during all of this put the tank back on to see if for some reason the tank being on and having more fuel pressure makes a difference but nothing changes.

 

I am just baffled by the fuel flow into the throat, with no pump or other pressure and just sitting there.
Is it both carbs doing that? or just one?
If you get the carbs off again with the body at an angle, as we mentioned, and the float just barly touching the needle valve and spring, let the float settle and suck on the fuel inlet pipe. See if it will hold a vacuum with your mouth. If the casting is cracked or something like damage around where the valve seat is attached, it could allow a seepage even when the valve seats securely. I used to do that with carbs to see how well the needle would seat and exactly where the valve shuts off and float levels.

 

I’m off Friday and I’ll look at it again to confirm, but I do believe it’s both carbs.