Choke not working:

I'll check my carb when I go home to see where the mix screws cap is, seen couple different areas where the mix screw may be on the carb guide, so I may ask before I drill.

Hi Twin's, Leo.
Boy, have you guy's got patience, even after all these years. R.G. too. Richard, it can be hard to get your mind around what these guy's are saying to you, but it isn';t all that difficult. Think simple. Carb's are a very basic, simple way to provide fuel to the engine. On the BS 34 carb's, as CDN stated, are extreamly lean running. The mixture screw's are on the top of the carb body, under the brass cap's. A small hole is in them most of the time. Just really a tiny pilot if you will. Use an 1/8" drill bit to open that tiny hole just enough to get a sheet metal screw into the brass. Don't go in too far with the sheet metal screw. Use either a real good set of diagonal cutter plier's, to pull the plug out, or needle nose Vice grip's. Pull straight up and out. It help's to mount the carb LIGHTLY in a vice so it is steady. The plug's can be quite stuck into the carb body, but a steady, even force will get them out. Using the guide that Leo gave you a link to, get all the passage'sreally clean. Some say to NOT use wire because it will damage the passage. Yea, that can happen, but just use descretion. After all it is aluminum. On the 34's, because they are lean to start with, as RG stated, the pilot circut is very small and the #1 area of problem's. It can look clean, even have carb cleaner go through it, and still be dirty. Carb cleaner is under pressure, where as the fuel mix is under vacuum. Big difference. Here is where there is no such thing as to clean.
Ok, now for part's. Mike's has a very good selection of the thing's you need to rebuild the carb, from floats to gasket's to jet's, ect. I think Merc has them too. 650 Central.
On another note, once you do these, you will be giving advice on what worked for you.Try remembering that they are simple, allbeit small, device's. It can be hard to not overthink about the problem's. Could it be this, or could it be that type of thing. Get one area done up correctly, then move to the next, by doing what your doing, asking question's.
One more thing, sorry. Make sure your filter's are new. If you put on a filter that used the wrong way, guess what, you just put all that crud into your nice, freshly cleaned carb';s. Same goes for the line's.

The mix screws on your BS34s are located in the towers on the front top portion of the carb, where it inserts into the rubber manifold. This one is uncapped and you can see the mix screw set down in the tower .....



If the caps are still in place, this is what you'll see, a brass plug with a small hole in the center .....



As mentioned, drill into it but not all the way through. It's easy to damage the screw slot on top of the mix screw if you do drill all the way through the plug. I use a sheet metal screw with the point blunted to extract the caps. I screw it in tight, keep turning until the plug spins with the screw, then yank them out with some vice grips .....

Thanks Gordon,The filters your talking about, are they air or fuel filter? And 5twins I see what your talking about (thanks)

Well, both. But on a fresh rebuild, I do both. But if the air filter's are like a week or 2 old, they should be ok. Check your oil, too. Take a little off the dipstick and smell it. Doe's it smell like gas or turpentine? If yes, change it. The oil 'filter's' are brass screen's, so a good cleaning would be ok. On the bottom of the engine is the sump filter, and it usually is torn in one of the corner's. Mike's or Murph has them along with the gasket's. But to get the carb's straightened out, just a dump and refill is ok.
BTW, the sump plate has to come off, and it is a mother fucker. Be extra cautious with the tiny 6mm bolt's, they will pull out of the engine case, and then you have another repair. The big bolt is the one that's removed to drain the oil, this can be a prick, too.

Thanks, I got one drilled, but went a little too far, didn't damaged anything but is there a trick on getting out because the screw doesn't seem to work, I might can be careful and drill more of the brass out, so what you think?

Thanks Gordon and 5twins you were right, got the brass caps out with the sheet metal screw, removed and cleaned, made sure mix screw outlets and all by pass holes cleared, made sure choke feed tube cleared, took out main jet, cleaned and all passage way cleared, cleaned float bowl feed hole cleaned and (yes) I could see light. cleaned pilot jets and passage ways. mix screws 3 turns out. Put back on bike, fired her up and still no high idle, I'm thinking the vacuum isn't working right, going to check my fuel petcock out. And btw, O ring looked great in mix screw area.

Did you do a bench synch on them? Are you saying you have a high idle, or you cant get it to idle at the preferred speed? Idle should be around 1200rpms when warmed up. You may need to adjust your idle screw to bring the rpms down or up, but first you really need to synch them. Glad the o ring was in good shape, it can cause ALOT of headaches for such a tiny piece.

I'm saying have low idle with choke pulled. If your talking about the butterflies, they opening up together, I didn't separated the carbs. it will start and run, then dies. I was thinking maybe bad or clogged petcock.

I did look in and the butterfly were slightly opened, with the synch screw which way do you turn to open clockwise or counterclock wise? and can I do this while carb on bike?

Hey guys, I'm ready to scream it was suggested for me to turn my idle up, so I turned it up about 1/2 turn now it backfires on both mufflers, what the heck is going on, I want this fix so I can ride

Hey guys, after doing all that work, I had that carb on and off so many times I think I could do it blind folded when I try to start bike with choke on, I have to use some throttle to start it and it will run for awhile and then shut off, would a bad petcock do this if the vacuum wasn't working right Now I did turn the idle up and kept gas going and it did backfire through the exhaust, I just don't understand and now very discourage about it all, I'm think about draining gas out of tank and taking off my petcock to see if the vacuum is clogged.

What happens if you run it with the petcock in the prime postition.

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I haven't tried that yet, I'll try that now and let you know.

I started bike on prime position, didn't make any difference, did notice a small gas leak thou, have to fix it.

ok guys, took carb off again because I notice a gas leaking, cracked hose, so I replaced the bad fuel hose, while I have the carb out I'm doing a bench synch on it, here is a pic, I have it position so the light going through it, didn't open it up much and I guess the idle screw will adjust the other side once I have it back on.

Nope, the idle speed screw on the left carb will adjust BOTH butterfly plates at once. You really do have some learning to do.

Back the idle adjustment screw on the left carb out so it doesn't touch the cable arm at all. That will have both butterfly plates closed, fully if the carbs are in sync. Hold the carb set up to a good light as you did above and look at both plates. Adjust the sync screw to get them both closed right up. Turn the idle adjust screw on the left carb back in until it touches, then about one turn more so both plates are just cracked open a hair.

Will do (thanks for your patience with me) I've so frustrated trying to get it right.

Ok 5twins did as you said, now both butterflies are the same with being a hair open, The last time I had the carbs back on the bike it still didn't want to run right, it seemed like it was trying but with choke pulled had to use the throttle to start bike and it run for maybe minute then dies, now I did have spray coming out of all those holes you mentioned (now not shooting out, but coming out) Also took my petcock off and it seemed good, so where do I go from here?

Well, I think you need to determine whether this is a carb and fuel delivery problem or electrical in nature. Many times, an electrical problem will seem like a carb or fuel one. I would run the bike until it dies, then drop a float bowl (carbs still mounted) and see how much gas is in it. Is it full or nearly empty? Full would point towards an electrical glitch.