Hey guys, I've been working on an '88 CBR600 I got back in April
and compared to the Buell Blast I used to have, I'm loving this bike and the countless nights I've spent taking things apart on it and doing my own repairs.

I recently pulled the carbs out to clean them out because the idle was a little rough and the rpms would take a while to drop after a throttle blip as if hesitating. Sadly, I think I might have made things worse. Even though the hesitation is mostly gone, the bike sounds a lot rougher on idle and if I've been riding around for a while, come to a stop and let the engine idle again, I get loud clicks from the carbs and the RPM's drop with every click and sometimes they get bad enough where consecutive clicks completely stall the engine and it shuts off. My best guess is that the vacuum slide/piston/diaphragms/whatever-they're-called are getting stuck. However, this only happens at around 1.5k or below.

Also, here's the current condition of my carbs:

Previous owner used silicone sealant on float bowls, OEM gaskets were worn
and since I only had a weekend to get my bike up and running again, I cleaned off the silicone and used another type of sealant. Carbs are not leaking at all.

Needles and jets inside the carbs might be aftermarket, and if they are, the jets from carbs 2 and 3 could be of the same size, which would maybe explain why the air/fuel mixture screws on carbs 2 and 3 are at different positions relative to carbs 1 and 4, in an attempt to compensate for not having different sized jets.

The only indication that needles might be aftermarket as well are the washers and notches that don't appear on any pictures in the manual. (As far as I know)

So yeah, I don't even know where I'm going with this, I've lost way too much sleep already haha. I just want my bike to run decently, it's my work bike after all.

 

adjustable needles are aftermarket, if your carbs have 2 of those and 2 stock that's not good. I had to purchase new float needles for mine as every time i cleaned the carbs it still had issues, was told its best to replace them if you have them apart. Then adjusting the carbs is another issue with mix match jet needles. your carbs may need sync'd which local shop here said $120 todo.

 

if you find out what the problem is please post what it was!! mine has been doing the same thing for 2 seasons now. in addition to that it also idles at 1200 or so when cold but when i drive for a lil while and come to a stop light the idle stays at like 2500 to 3000 rpms!! but the weird thing is if i let it idle like that it will kick back down eventually.. feels like 10 minutes haha. or if i hold the brake and let the clutch out a till it catches and let off the clutch or put in neutral and it idles back at 1200 or so again!! i know its running very lean. i changed the plugs last season and they were very white. im thinking obviously need to play with jets but never synced the carbs in the 5 years ive owned it and who knows if the last owner did anything to it besides throw a hollowed out vance and hines exhaust on it

 

@cobra:
From the people I've talked to, it seems that both my carbs and spark plug caps (hell, maybe even my coils) are messed up. The clicking noise could be current arcing, causing a misfire.

@itsahurricane:
My bike had the exact same symptoms, which is why I decided to take the carbs apart in the first place. From what people told me, one of the diaphragms could be torn.


Today to see if I can get my bike running a lot better, I'll be getting replacement spark plug caps (though used) for all 4 cylinders, taking out the carbs and setting the air/fuel mixture screws to manual specs, I'll make my own carb sync tool and sync them. I can't sync them or do much for the carbs right now because of the erratic idling so I'm really REALLY hoping that the replacement caps take care of the arcing problem. If not, I have a set of coils coming in anyways. As for the punctured diaphragms, I'm going to try applying flexible silicone sealant in a very thin layer and see where I go from there.