Misfiring at idle and low speeds

[zookrick]

So, my GSXF 750 teapot misfires after fully warmed up at idle and below 2-3000 rpm. Idles cold just fine.

It takes about 20-30km for it to get warm/hot enough to misfire. I only let it idle when syncing it just the way I synced my GS carbs and never had a problem. Do need to take it for a long ride before syncing it or is there something else going on here? Ignition is fine, has dyna coils and relay mod.

I have gone through the carbs over a dozen times making sure they are clean.

 

[suzook12]

Sounds like she might be a bit rich at idle

[zookrick]

Ok, I didnt think of that since it only misfires on one cylinder.
I have a 37.5 pilot jet (stock) with mixture screws at 2 turns maybe I will try a 35 pilot and 3 turns.

edit: those are fuel screw not air screws so I need to turn them in, they are already at 2 turns, so 1 1/2 or 1 1/4 turns?

1 3/4 is stock but this bike is far from stock.

Edited November 9, 2017 by zookrick
brain fart

[banoffee]

Had same problem, mine turned out to be tiny cracks on the plug caps.

[Macduff]

I think it will take a very rich mixture to make it misfire , and your settings don't sound too rich, I think lean mixtures tend to misfire more than rich with too rich just loosing power . Its not clear reading the 1st post if the problem has always been there which could indicate a carb blockage somewhere , could be a float height issue on the cylinder affected or for my money sounds like leads plugs ignition related. 

[KATANAMANGLER]

Sounds like it might be electrical. I say that for 2 reasons:

1. You've done the carbs to death.

2. It manifests itself when the bike is warm. ( heat makes an electrical resistence issue worse)

Check the resistance on the coils, plug caps and pick up signal generator. If they check out then borrow a spare  CDI and try that.

Swapping the other paired plug cap and feed from the coil that feeds the misfiring cylinder will also tell you if its particular to the lead and cap. Does the cylinder missfire move etc.

Some people will tell you a CDI works or it doesn't this is untrue. I had a CDI last year that had an intermittent signal failure to one coil. I replaced it and hey presto.

Check your feeds from the cdi to the coil live and signal for continuity.