CB750F Idle help!!!!

Hi Folks! First timer over here. I've been running a 4 into 1 exhaust from Carpy and its been running great until i noticed the spark plugs had a whole bunch of soot on them. i pulled and cleaned out the carbs, cleaned the plugs and now the bike won't idle. I set the idle mix screws to 2.5 turns after lightly seeting (sp?) them. If i give her some gas she will start but idling is an issue. Right now, i do not know what to do and am thinking that in order to adjust the engine from running rich, i need to adjust the jet needles. however, the stock needles are not adjustable. do I have to buy adjustable needles? if so, where? I tried looking and cannot find any.

any help troubleshooting would be greatly appreciated! Cheers!!

Keihin VB42A

If your bike was running fine but rich, you've made a mistake somewhere in what you did to your carbs (assuming you've got your plugs back in properly and the right caps on them). Did you notice what the idle mixture was when you started? That would be the best place to return to and start working from there, but I've guessing you've missed something in cleaning your carbs.

i'm not sure what I missed. I wouldn't say the bike was running fine because i found out the hard way one of my floats was cracked. After replacing, i took to the highway and she ran like a dream. On the way back she started bogging down and i wasn't getting the full response on the throttle to the point where at a stop, she would die and i'd have to give her a little throttle. Now, i took the plugs out and cleaned them, I messed with the 4 mix screws and idle screw to the point where she is backfiring and won't idle. The throttle repsonse is there though. I took out the plugs to take a look at what is going on after that and she is still running rich. It leads me to believe that if there is an adjustable jet needle for my carb (Keihin VB42A), i need to buy them to lean out the mixture. I also checked the butterflies and made sure they were all opening correctly. I probably could adjust them to what i've found online. I can pull the carb apart again and clean everything all over again, but i just don't know what's wrong. pretty frustrating if you ask me.

1. I know this is going to sound idiotic, but have you checked fuel level? My kid was complaining recently after working on his Buell that it was running crappy and would die at intersections. I rode it and sure as heck he was right, I then put the bike on reserve and rode it to the gas station where I fueled up and it was fine. Sometimes we lose track of how much fuel we used while working on them.

2. Have you checked the intake manifolds, it may be coincidence, but maybe one cracked or was knocked out of seat.

3. Did you sych the carbs. ? If the carbs were synched with the cracked float, you need to synch them again now the float issue is cured. If it was running rich, it maybe the float levels are off.

4. Is the timing still on? I know this sounds odd, but I've found in the past, my issues are usually a combination of a few things. For me it's never just a clogged jet, it's usually the jet is clogged and oh by the way your petcock decided to take a crap at the same time....

I wish I could be more help, but I'm just going over the issues I've had in the past. Finding the stock specs and starting from ground zero is always the way I start. I know when I'm dealing with carbs. I usually have to take them off two - three times to get them right. This is never fun, but getting them set right in never an easy task for me.