As far as I know, the old manifolds had a gasket and should be used with sealing compound to be free from leakage. Therefore the next generation of manifolds was designed with an O-ring.
The new manifolds i have installed 4 weeks ago have the o-ring only and it works great. I wouldn't use both.

So yesterday i removed the carb and took it apart. I tried to remove the diaphragms carefully, but without success. since it has been raining here for the last moth and because the forecast promised sun today i did not have the guts to risk screwing thing up(would have been the first ride of the season). However, i noticed that the diaphragm to the rear cylinder carb had a small area that was brown (approx 1mm i diameter) on the "piston side" and a bubble in the rubber (same size) in the same location but on the "top side". I used some rubber cement (small amount) to patch it up. Before i removed the carb from the bike i checked the fuel level in the bowls and noticed that the fuel level in the rear carb was a bit low, approximately 4mm below the mating surface. So i checked the float height with a digital caliper set to 15.8mm and one of the halves of the float was indeed touching the caliper. So i readjusted the float and put the carb back together and mounted it on the bike. I checked the fuel level and the level was pretty much spot on. The mating surface was almost perfectly in between the top and bottom of the U-shape in the tube (due to surface tension), so i guess the level is ok?
I started the bike and it sputtered much so i grabbed my colortune set and started with adjusting the rear cylinder. The mixture was rich so i adjusted the pilot screw so that the flame was blue. At this point the bike would idle better and the sputtering had stopped. So i moved on to the front cylinder and i could hardly see anything else besides the spark, i.e no flame or a very weak one, not even when pulling the throttle. I went for a ride and there was no power in the bike and a very muffled sound from the exhaust compared to before. During this process i replaced the manifolds.

My questions are the following

1. what is the best way to replace the diaphragms? i have read that you should cut away the metal ring on the top and then use superglue to hold the diaphragm in place. Another method i have read about is one where you use a small screwdriver to push the plastic ring down in order to pull the old diaphragm out. The last method is to just tear the old out and use dental floss to coax the new in .

2.could the muffled sound, and engine running on one cylinder(spark+no flame=no fuel?), be due to a vacuum leak or bad sealing between manifold and mating surface? i had a bit of trouble mounting the carb on the bike due to the new manifold not being as soft and worn out as my old ones and in all this frustration i might have forgotten to connect the vacuum line to the petcock on the right side of the fuel tank (embarrassing if so). This could explain the lack of flame/fuel. The bike is currently at my parents house so will check this tomorrow on my way home from work.

3. upon removing the piston/diaphragm assembly i noticed a small amount of black particles in the cavity where the choke tube goes(under the diaphragms seen from the top). Is this coming from the small filters and if so can these be removed without any impact on the engine? if not, do you guys know of any suitable replacements?

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The reason why i suspect that the problem when braking is originating from the carbs is because i find raw, unburnt, fuel in the air intake to the rear cylinder carb each time i disassemble the carb which to me indicates an overflowing carb. This is my first motorcycle and my thus my first experience tinkering with one. My conclusions are therefore based mainly on what i read on different forums. In all my reading i have not found anyone with a similar problem With this said i welcome all suggestions and possible reasons to why i have this problem.

Another reason to why i suspect the carbs is that the guy that owned the bike before me did was not much of a mechanic. I bought the bike i "working" condition and since i did not have any license or had even driven a motorcycle before i had no way to test the bike other than to trust the seller and watch him test drive it. Once i had the bike at my place i went through all the hoses and connections and found that the previous owner had been running the bike without the vacuum hose to the rear cylinder, just to name one example. Who knows what else he has had his fingers on

A little update: It turns out that i did indeed forget to connect the vacuum hose to the front cylinder petcock. After reconnecting it i synched the carbs and adjusted the pilot screws and it turns out that the new manifold did help a lot. The bike runs smoothly throughout the rpms and there is no sputtering. Before i had to set the idle at 1500 to prevent the bike from sputtering when releasing the throttle. Now it runs "flawlessly" on 1100-1200 according to Haynes. However the problem that occurs during heavy braking still remains. I will take a lok at wires as you suggested Rant and get back to you guys. I just had another wisdom tooth removed today and i am currently on citodon so both me and the bike will have to rest for a couple of days.

Hello everyone!

Some time has passed since i last posted here and i have had som time to keep on figuring out the cause of my problem. It pains me to say that i am still at square one. Yesterday i replaced the carbs with a pair i bought from ebay without any success. Unfortunately the drain plugs to the bowls of the new pair were damaged so to speed up the process i took my old bowl and mounted them on the new carb. To completely rule out the carbs i will replace the old bowls with the new ones this week when i have removed the stuck drain plugs ( which are really stuck with destroyed heads as a bonus ).

One question arose when i cleaned the new carbs: There is a small hole in the lower parts of the bowl which at first glance seems to be connected through a long drilled hole to the port and the small brass tube attached to the carb ( i think its the overflow tube). The thin brass tube on the carb is inserted in the long drilled hole when mating the two parts. To my surprise there seems to be a brass plug in the drilled hole which cuts it of from the small hole in the bottom of the bowl. Is this supposed to be plugged and if so, what would happen if this plug is removed for some reason ( by previous owner).
One of the replies in this thread mentioned replacing the carbs to solve this problem, and since i have replaced the carbs except the bowls i want to know if this hole should be plugged or not.

Are you sure that this it is a jet? I went in with a borescope today at work after a few hours in the ultrasonic cleaner and there was only a small indentation in the center of the plug probably made by me poking around with a thin steel wire trying to get the worst dirt out before the ultrasonic cleaning. If this is indeed a jet, do you know the diameter of the hole because i tried sticking in a 0,7mm wire while looking down with the borescope and the wire diameter was at least twice that of the hole.

In the attached picture:
#1 Green arrow: What is the function of this hole? it is above the fuel level in the carb so i guess its not for sucking in fuel to the choke.
#2 Is there a free passage in to air/fuel flow (main flow in to the cylinder) through the brass pipe? If too much gasoline is forced in through the green hole during braking could it overflow into the "main flow" given that the hole is plugged?
#3 If the hole is clogged, wouldn't this mean that the suction end brass pipe is constantly under the fuel level? Is there only a suction of fuel/flow of fuel through the brass pipe when the choke plunger is in an open position?

Many questions at once...