I am desperately in need of help!
I own a TR1 -81 and have the following problem.

When braking or going over a speed bump without a bit of throttle the bike wants to stall.
Whenever I do semi hard brakes the engine revs down and if I give it too much gas just after stopping the engine backfires and dies, sometimes so violently that the carb jumps out of the the intake manifold. What I usually have to do is jerk the gas two or three times quickly. On the fist jerk, you can hear the engine "struggle" and after the second jerk the engine revs and sounds like normal. I've have pulled the carbs many times in order to set the float level but without success. Every time I pull the carbs there is a little bit of fuel in the intake manifold on the air side of the carb to the rear cylinder.
Apart from the braking and speed bump issue, the bike runs fine. There is some occasional bakfiring when decelerating  and a little bit of fouling of the rear spark plug. Furthermore, if the bike sits for some time and I start it up and shut it down immediately it will only run on one cylinder when I start it up again due to a fouled rear plug.

I have replaced all vacuum hoses and fuel hoses, the carb has been cleaned using ultra sound, I have rebuilt the carb(jets, needles, pilot screws, etc).
After searching the Internet for quite some time I have narrowed it down to incorrect float level in the rear cylinder carb. I have tried to adjust this level without any real success. I have been pretty careful when adjusting the floats and have only done minor adjustments to the tang (maybe too careful, meaning no real adjustment). I did make sure to set the level according to the specs in the Haynes manual, by measuring from the top of the float to the mating surface(at least I think I did).

What do you guys think, is it float problem or something else?
To prevent the bike from dying whenever I brake I set the idle to approximately 1500rpm. This helped a bit but still, the bike wants to die during medium braking and dies completely during hard braking(panic braking).
I have synced the carbs and set the mixture screws with colortune.

Hallo  Benghan,
Have you searched for air leaks, are the intake plugs tightly attached?

I have never ever heard of brakes effecting a carburator. maybe if we'd talk about cars with powered brakes, but not at a bike!
So it has to be the change of the air flow, the change of RPM or the fuel in the carburator that moves while braking. Therefore I thought about the membrane...
Or the needles might not seal the Jets, so the fuel can pass them while breaking? But i've also never heard about this  
maybe the needle of the floats does not seal properly? To mention another idea...
The fuel within the gas tank also moves while breaking. So maybe this could effect the pressure to the floats.

It is hard to say what the reason is, since you have done everything. I would try  to remove the vacuum hoses from the petcock, close them and go for a ride with the cocks on PRI,
may be it helps, may be not.  What you describe sounds like a much too  rich mixture at idle,
Regards Ali

Quote from werner r. on 28.03.17 at 10:53:00:


Thank you for the replies! I replaced the petcock membranes last summer so they should be fine. I will definitely try your method anyway just to be sure Ali.
Any thoughts on measuring the fuel level in the bowls? Can this be done with the transparent hose method with the carbs on the bench or must this carried out with the carbs mounted on the bike and the engine running?