Stalling issue when coming to a stop

Carb cleaner again used for checking leaks. Its best used with small tube to concentrate spray in specific areas. Idle will change if leaks are detected. Check around throttle seals too. Mine were located there. JC
 
You say you transferred the floats from your '82 carbs to the '80 carbs. That would be plastic floats put in carbs that originally had brass ones. The swap is supposed to work but be aware that the two float types have different setting specs. The original '80 brass floats are set at 27.3 ± .5mm. The plastic float spec is 22 ± 1mm. Even after setting by measuring, it's best to verify your fuel levels externally using the clear tube method .....

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My buddy made this mistake when putting plastic floats in his '80 carbs. He tried setting them to the '80 brass float spec. Needless to say, his fuel levels were all fucked up, lol.
 
Interesting, so these carbs I believe are off a 1980 special but they had plastic floats. The only reason I changed them was bc they were a bit corroded and the pins were sticking.

Here's one of the new carbs:
full
 
The "tell" would be the float bowl style. '80 carbs still had a drain bolt like the BS38s. The '81 and later BS34 carbs got a drain screw angled off to the side. If you have those bowls and a pull knob choke, they could be '81 carbs. '82-'83 carbs got a cable operated choke and were painted black. Here's the '80 bowl .....

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..... and the '81 or newer bowl .....

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The newer bowl style makes external bowl fuel level checks easy. Just attach a clear plastic hose to the drain nipple on the bottom of the bowl and open the drain screw.
 
Interesting so looks like these '80 carbs are '81+ since the drain plug is off the side, explains why they also had the plastic floats.

I ordered some new intake manifold gaskets, choke seal and throttle seals hopefully that does the trick.
 
You should consider getting some longer screws for your float bowls. The ones you have are too short and only grabbing a couple threads in the carb body. They will strip out pretty easily. You want something that will reach all the way through and engage all the available threads. M5 x 16's work well. You may be able to use some of those short ones on the tops. 10's (no bracket),12's (one bracket) and 14's (two brackets) work best up there though.
 
Got back out there today now that the rain has stopped. I replaced the choke dust seals and all 4 throttle butterfly seals and ran the carbs through my ultrasonic cleaner. The bike still only starts with the choke on even with #45 pilots and the mixture screw 3 turns out. It was 20 degrees cooler out today and the bike could barely idle but mostly just died.

I tried the wd-40 method going 1 intake manifold and carb at a time but didn't seem to have an effect when the bike was idling. The lines to the intake manifold and petcock are secure and new, is it possible the petcock has a vacuum leak?
 
I should also mention I was able to ride it up and down the street and it seemed almost normal last weekend but I was tuning and test riding in the rain. Maybe the rain was blocking a vacuum leak elsewhere? The day before I put these carbs on my neighbor backed into my bike and knocked it into my other bike, doesn't look like there is any damage but is there a way to test the cyl head for vacuum leaks as well?
 
Do you have a small bottle/can you can fill with petrol and add a length of tubing so it can be connected directly to the carbs just in case there is an issue with the stopcock? Perhaps you have tried this already?

Do you have compressed air to blow out the choke passage ways from both directions in case of a blockage? Can you thread a piece of fine wire or fishing nylon through to check for a blockage?

Is the carb sync way out on one cylinder so the butterfly is completely closed?

Have you ruled out an electrical problem?
 
Below is a section cut from your carburetor photo:
Screw.jpg

It has been mentioned previously that you require longer screws to hold the carb bowls in place. Highlighted in the photoclip you will see that when the thread was originally cut it also left some partial thread marks above against the side of the carb body. As neat as these appear they are often not fully formed threads i.e. not cut to the correct depth. This is because the original machining was done with a tapered tool. If you insert too long a screw then when it runs into those partial cut threads the screw will be forced slightly outwards with the potential of cracking the carb in that cornor. This was potentially a major issue on my BS34 carbs and luckily I noticed this when gently screwing in a long screw and finding it would not go in any further with ease. I then cut all my new stainless screws to the correct length.

Have fun.
 
Today I tried
1. replacing the gas (it was about a month old)
2. replacing the float bowl bolts with longer bolts
3. double checked the float height
4. replaced one of the intake manifold gaskets

The bike starts and is running about 90% still a little bit of a hanging idle but Im able to take it on the freeway and it isn't stalling. Not sure which thing fixed it or maybe a combo of the above but hopefully just a little fine tuning, re-syncing the carbs and it will be back to normal.

Thanks again for all the help!
 
Do you have a small bottle/can you can fill with petrol and add a length of tubing so it can be connected directly to the carbs just in case there is an issue with the stopcock? Perhaps you have tried this already?

Do you have compressed air to blow out the choke passage ways from both directions in case of a blockage? Can you thread a piece of fine wire or fishing nylon through to check for a blockage?

Is the carb sync way out on one cylinder so the butterfly is completely closed?

Have you ruled out an electrical problem?

Thanks this made me think about how old the gas was, I have an aux tank so tested with that
 
Are you using stock-like thick (about 1/8") intake manifold gaskets? Many of the replacement manifolds come with plain thin paper gaskets. I wouldn't use those, they may not seal good enough.
 
The bike still only starts with the choke on even with #45 pilots and the mixture screw 3 turns out. It was 20 degrees cooler out today and the bike could barely idle but mostly just died.

Keep in mind that the choke is an enrichener, regardless of what the ambient temperature is. So, to say that the bike will only start with the choke on is stating the known. Yeah, my bike will only start with the choke on too........
Now, once you've been out riding and then stop for a break, it may restart without the choke.....and maybe not, depends on how long that break was......or something......

Mine usually starts with the first kick, choke on. As soon as she's running I'm shutting the choke off and getting ready to feather the throttle - just in case she decides to falter. Other experiences may vary.
 
Yes, these bikes pretty much all require the choke for a cold start, even in warm weather. It won't need to stay on long in hot weather but usually is still needed for that initial start.
 
Interesting. for me I've never needed the choke on the previous bs34s or the mikes pwk carbs unless its <50 degrees. We'll see how the cold start is on these tomorrow, today I used it but it also fired right up at 3-4k.
 
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