Gents, you are all geniuses.
Ha. I can't believe it was that simple!
Blocked the Vacuum tube.
Carbs balance up almost immediately.
10 minutes of tiny tweaks and I'm done. No point messing any further.









I shall call them Balanced.
Time to go rebuild and go for a ride!!!!

Many thanks for your help.

I've just been experiencing this exact same problem after I've been 'balancing' my carbs today.
The pressure on the carburettor with the vacuum hose attached was way down, so I assumed it needed balancing.
This forum is ace.
Just hope the blocking trick works when I go back to it tomorrow.
Started messing around with the fuel screws before I gave up, so that should be fun sorting that out now!

Well, exactly the same happened to me few weeks ago. I prepared old petcock I'm using for blocking vacuum line but I forgot to connect it. I figured only after I dismantled carbs completely. Well at least I have checked/adjusted floats :)

Dragging up an old post..

Took apart my carbs and replaced all orings and gaskets with Litetek kit (thanks Blair), including carb cleaner and compressed air through every hole.

Upon refitting to the bike today, the bike will start on choke as it should, but once I take off the choke and rev it, the Revs will hang and slowly drop. Then after another 15 seconds or so the bike will cut out.

I put a screw into the vacuum pipe mentioned and it didn’t make much difference. Is there a better way to block this off? Also, I am using an external fuel tank and have connected this to one of the two fuel lines on the carb. Do I need to get a t-piece and connect to both fuel lines?

I have a Morgan carbtune so will get this hooked up tomorrow and look at balancing the carbs (inverted). Can I balance it while on choke or just increase the Revs by the idle screw?

Thanks in advance

Hi Hutchy.
I'm sure everyone in this forum will back me up, but if you're using an Auxiliary (external) fuel tank you need to supply fuel to both hoses.
If you don't then only two of the bank of four carbs will be getting fuel and only two of the cylinders will run/fire.
I bought one of these to do the job and hold enough fuel to balance the carbs + go for a test ride.
Expensive, but well worth it and you can mount it perfectly on the left side of the frame where the rubber fuel tank mount is.
https://www.carbuilder.com/uk/twin-cham ... gI-YvD_BwE
Good luck!
Hubbsiboy

Here you go -
Visual representation.
https://app.box.com/s/gknv56q7fx9qz4pbmqiairm0r1zacj3p

Hi Hubbskiboy,

Thanks for the quick response. That looks much better for this task!

In the meantime I’ll probably just have to get a t-piece for my current setup or just put the tank on, even though that’s a lot of hassle.

Hopefully that’s what it is!

what bike is it? Thought most 400's had only 1 fuel inlet

Nah Mofo.
Our GK76ers have two. Thought you'd know that!
https://app.box.com/s/b370b181f9svv3g32r0fz3cie9o76yp6

To be fair, I thought it would only be one too considering one line is from prime and the other from reserve.. but can confirm today that there was no fuel in floats 1 or 2.

A new fuel line and t piece allowed me to hook up to both fuel lines from the carbs. Larger screw shoved into carb #3s vacuum line and ready to go.

Time to fire her up.. it ran like sh*t.

Would still hang up at 4K revs, and could only get it to come down by turning the idle screw slightly.. then it would sit at 1.3k rpm for 10 seconds and cut out.

I changed my fuel mixture screws to 2 turns out, instead of 1.5 and again, it ran terribly, stuttering and hanging revs. With the full new orings and gaskets from Litetek installed, as they should etc. I was ready to burn the bike.

I persevered and after turning all the idle mixture screws back to seat and then out to 1.75 turns out.. it seems happy to idle as long as you want it to. Fully balanced using the morgan carbtune inverted and it’s as close as I’m going to get to balanced.

Not had a chance to take it out yet due to the rain coming on, but will get it out tomorrow and see how it drives through the Rev range. As it stands it revs up to 8k beautifully, with no mid range stutter (needle clip 4 from top to account for exhaust and k&n filter).

Hoping that’s an end to this epic for a while!

Inline fuel filter ordered and awaiting delivery