Cylinder 2 and 3 only fire after giving it some gas.

Cylinder 2 and 3 won't fire on idle. My bike is currently straight piped and I can feel the exhaust is cold coming out of those two cylinders at idle. After I give it some gas I can hear all 4 start to engage.

I've tested spark and all 4 have it and they all have good compression. I replaced the ignition coils to see if that helped but it hasn't.

I still need to throw new plugs in it since it's been sitting for the last 20 years so it could very much be that lol. But any other suggestions are appreciated!

 

Some history might be helpful - carbs rebuilt? valve clearances checked? Running sync?

 

Carbs ever cleaned, really cleaned? Idle circuit in 2 and 3 could use some cleaning?

 

What do you mean by "straight piped?" Is there no collector fitted?

 

Just a guess but maybe the float bowls on those two carbs don't have the fuel high enough. That or as the other above have suggested, what have you don't (cleaning) to the carbs. Back ground needed as to what you have done with the bike.

 

If you can get it to idle, open the pilot screw on 2 & 3 and see if you can get it to fire. (I had a similiar problem on #1 and had the pilot screw out 5 turns in order to make it fire. Turned out that the intake manifold gasket was torn and it was sucking a lot of air.) If it fires after opening the pilot srews then you need to clean the carbs. You should also use a little propane around the intake side of the two carbs and see it that causes it to fire. If so, you probably have a large air leak.