Hi chaps,

I’ve been reading all the good info on here about sorting out the carbs on the GK76A.
I have followed all the advice I can and definitely learned a lot on the way! (Like always buy a set of JIS Screwdrivers!)

I have just finished refitting the carbs to my wee bike after a full strip down, clean and rebuild using the full seals kit from Blair @ Litek.
I have managed to balance carbs 1+2 to each other and carbs 3+4 to each other using a CarbTune Pro - Bank 1+2 is sitting about 20cmHg and Bank 3+4 is sitting about 10cmHg
But when I adjust the centre carb/Throttle screw to balance both banks to each other, the idle speed goes up to about 3500rpm and the Idle screw has no more adjustment to give to bring it back down again.

Any ideas how I can get the two banks balanced and then bring the idle down to a nice reasonable level?
(All pilot screws are set to 1.5 turns out. Don't know if that makes a difference)

I was thinking of adjusting the throttle cable setting nuts on the carb a touch, but they are pretty difficult to get to when the carbs are on the bike.

The other issue I have noticed is that when I rev the bike, the revs are pretty slow to drop back to idle speed.
I have a feeling that I have air leaks somewhere and need to sort them out

Any advice would be appreciated.

Thanks

Just a quick check - you did block the vacuum tube before starting?

quick check - try to swing handlebars from lock to lock once carbs are balanced and idle is too high. if idle speed will raise even more then your throttle cable line set too tight. there should be adjustment screw somewhere. bandits do have it at handlebar end of cable but Gixxer might be different.

Don't mess with the carb screws, other than the carb sync screws, may end in disaster lol! Spray barb/brake cleaner around the manifolds and see if idle speed picks right up. If so, there is a large leak.
If you have the OEM manifold clamps make sure they are clamped right up so the 'ears' touch, otherwise it will let air in.

augerment wrote:Just a quick check - you did block the vacuum tube before starting?

+1 with interest!!!! i learnt this one the hard way.
Dont do anything until you have blocked this off.

Thanks guys. Really appreciate the feedback, some good info here.

I'll try the handlebar check and the manifold clamps on the weekend as suggested by moforockband and ventYl .

Now augerment & KiwiBiker, the Vacuum Tube. This has me interested/worried .
No I have not blocked this off.
By the Vacuum tube, I am presuming that you mean the little 1cm long tube poking up from manifold inlet number three (Third from the left hand side of the bike, facing forward) that is normally connected via a hose to the fuel tank petcock?
I have left this open to atmosphere, as I have removed the fuel tank and am using an external auxiliary tank to feed fuel.
What difference would blocking this make? (well, I can always try it to find out )

Are you using a slave fuel tank? If so (and it's much easier). There should be 3 tubes coming from the fuel tap - 2 supplying fuel and the vacuum tube. Simply unplug the vacuum tube (at the fuel tap end) and plug it with a small screw.
Then try re-balancing. It won't work with the vacuum open to the atmosphere...

Not blocking the vacuum tube leading from 3rd carb adapter into petcock may lead to vacuum leak behind carb #3 which in turn leads to wrong balance setting on that pair. Or might lead to high idle RPM on it's own.

You must block the vacuum pipe
When you block this you will need to rebalance the pair of carbs that are vacuum pipe side then redo the bank of 4.

To allow for this the carb you already done will be way out.

After you've got them close go to the factory pro website and there is very clear info on getting everything spot on even down to using the vacuum gauges to set the pilot screws, worth a read.

Brilliant guys. I think you have probably nailed my problem

Yeah I'm using a Slave fuel tank as its so much easier without the regular fuel tank on the bike.
I'll block of the vacuum pipe and have a crack at balancing this weekend.

Really appreciate the advice
Thanks