Katana 550 exhaust popping

[waltfen]

I have a 1982 Katana GS550 that when warmed up "backfires" on idle through the exhaust. It does the same on the overrun.
I have checked all exhaust connections and air intake rubbers etc. and can find no leaks.
My next guess is to check the valve clearances.

Can anybody else offer any hints?

[brveagle]

all stock?

sounds like it's running rich..

how do the plugs look?

maybe a slight miss to a fouled plug

[waltfen]

Yeah its all stock. Bike runs ok when cold (though it always starts on 3 cylinders and takes a while before number 4 fires), but does run unevenly at idle when hot.
Plugs appear ok.
I did have a 4 into 1 system on which did not backfire as much and I know that it had loose connections where the 4 pipes went into the 1 silencer?

Normally it is a pop from the exhaust but it sometimes gives a resounding crack then stalls the bike.

[Dink]

Start with a thorough carb clean, then check valve clearences, then balance the carbs. It sounds like the idle circuit in #4 is grotty.

Dink

[waltfen]

Thanks for the rapid responses. As a newbie I ought to post a pic of my bike.
Here it is:-

[Mr_Shake]

That bike is sexy as h3ll.