1976 KZ back firing from one cylinder

Hi everyone,
I am new to this forum so apologies if this question has been treated before...

Just acquired a 1976 KZ 750 b, cleaned the carbs in unltrasonic bath, replaced the broken diaphragms and put new gaskets. I also got rid of the air box for two uni air filters.

I have reset the carb settings to factory ones (one and a half turn) but the left cylinder is backfiring quite heavily the bike idles at 2500 rpm and the gaz coming out of the exhaust are cold compared to the right exhaust.
Looking at the spark plug (brand new NGK), it looks flooded... So I'm thinking, my left carb is probably set too rich, there's no proper combustion as a result and the petrol backfires in the exhaust.

Well in fact, it´s apparently the opposite... When I put the choke on, the backfiring stops and the rpm goes down to a normal idle.
Which indicates that the mixture is too lean on the left cylinder (cańt understand the flooded soark plug but anyway...)

All this to say, not much of this make sense to me.... Unless one of you can enlighten me with your expertise on the KZ?

Another thing, I haveńt synchronised the carbs yet as just got a set of carb synchronizers today... Can anyone please tell me where I need to connect them on the carbs or onthe inlets... I cańt find anything on youtube about this for the KZ'

many thanks and sorry for the long post.
Christophe

please put air box back on

I can't... I made such a mess of it trying to extract it from the wrong side that it's now looking like it's been chewed by a cow. So I' m gonna have to sort it out with my UNI filters (engine sounds much nicer too

Any other suggestion or explanation on how to synchronize carbs?

Perhaps you can find a stock air box on eBay? Otherwise, prepare to become a carb experimenter. Ed

Yeap, it did cross my mind but only as a last resort solution... I want to convert it ibto a street tracker so the airbox is not an option at this stage.

Can anyone point me in the right direction, only advice so far is to give up on the air filters...
Any idea where I should connect the carb synchronizer please?

Looks ike your carb holders have a hose connecting each other instead of plug, but it does the same thing. Anyways you can pull that hose and use those nipples to connect your carb sync tool. Put some good air filter pods on it not any of those cheap one's.

Clabedan wrote: Yeap, it did cross my mind but only as a last resort solution... I want to convert it ibto a street tracker so the airbox is not an option at this stage.

Can anyone point me in the right direction, only advice so far is to give up on the air filters...
Any idea where I should connect the carb synchronizer please?

Carb sync hoses are attached to the vacuum nipples located on the carb holders.
The vacuum nipples are capped/plugged in normal operation except when being used for something else such as supplying vacuum through a hose connected to a vacuum operated petcock.

Before syncing, would suggest first installing an aftermarket carb kit designed for using with pods. Likely won't provide full range carb tuning as possible with the air box, but should help toward improving tuning ability throughout the entire range of throttle positions.

Good Fortune!

Clabedan wrote: I can't... I made such a mess of it trying to extract it from the wrong side that it's now looking like it's been chewed by a cow. So I' m gonna have to sort it out with my UNI filters (engine sounds much nicer too

Any other suggestion or explanation on how to synchronize carbs?

1) Install 50 pilot jets for start.

2) Use clear tube to set fuel levels in bowls (4.5 - 6.5mm down from lower edge of the top carb body).

3) Take bowls off and soak or flush them with carb cleaner (they have the jets in the bowls).

4) check for air leaks at the intake manifold joints.

As for tuning to pods: I would contact a dismantler and buy an air box. It won't cost that much.

duplicate

Patton wrote:
Carb sync hoses are attached to the vacuum nipples located on the carb holders.
The vacuum nipples are capped/plugged in normal operation except when being used for something else such as supplying vacuum through a hose connected to a vacuum operated petcock.improving tuning ability

On my 79 KZ750 twin, there is a crossover (equalizer) tube connecting the two vacuum nipples which is supposed to be there at all times.

Yep this is what I have too, as seen on the pics attached to first post

Many thanks guys, replies are really helpful.
Cańt wait to go and check all the things you mentioned !