Carb Sync Question for Jetted, piped bikes
 

I've got a sync kit on the way, as I never did it when I originally cleaned my carbs. Right now the bike is running very rich. I've got a jetkit in there, and a Yoshimura RS-3 WITH the upgraded manifold. I'm guessing this is going to change what type of readings I should be getting during the sync.

How should I be tweaking the carbs for this particular setup?

All you're looking for when synchronizing is ballance. Just adjust until all have the same amount of vacuum on all of them. The only way you're going to change how rich or lean the bike is, is with jetting. Do you have an O2 sensor installed, or have you put your bike on a dyno to determine fuel mixture, or are you using spark plug color to make the determination ?

I guess I'm just going by spark plug color, though I do have acceess to a free dyno. I have no O2 sensor. PO had the bike jetted by the dealer when he bought it new. Just going by the spark plug color, they're pretty dark for only having 2k on them. One of them was fouled completely and wet with fuel. I smell lots of fuel in the exhaust, and I'm trying to figure out why the thing is running so rich.

I know I could have two separate problems here, but I never synced the carbs when I originally cleaned them (2k ago) because I didn't separate them so I didn't think it was necessary. It was running fine up until very recently, when cylinder 4 fouled and stopped firing (though I can't get it to work again now). I figured I'd sync the carbs and that would either fix the problem, or I'd at least see what else was wrong once I was in there.

I was going to PM you and see if you could give me your two cents on it. Here's the thread describing my problems in full:

https://cbrforum.com/forum/cbr-600f3-17/sounds-like-lawn-mower-poor-acceleration-97899/

When a plug is fouled physically by fuel you can't just clean it and run it again. You need to just get new plugs. The fuel saturates the porcelain and reduces the effect/changes heat range, etc.

I understand that. I was merely doing it as a troubleshooting measure to just get the plug sparking again, as I didn't have another handy. I just needed to see if that was the only problem, or if something more sinister was at work.

BTW what brand\type plugs should I have in there? I'm running NGR R's right now.

NGK's are the brand you should use, upgrading to the R's isn't really necessary, you are only jetted, with intake and exhaust. I would call dynojet and ask them what jet kit you should be running, read up on how to jet a bike, like when it spits in decel what it means, what it means to have flat spots etc. Reading up on these articles will save you a lot of time and effort on the internet. Also it will help you a whole lot more than just asking for the answers i.e. having an understanding. If u don't know the meaning then the answers are merely words.

I agree with the advcie completely but this wasn't a problem for the first 12,000 miles, so I have to assume the jet kit was appropriate, and properly installed and tuned. It was professionally installed, and I know that can go either way, but the bike ran GREAT. No sputtering, flat spots, ANYTHING. Something clearly has recently just "broke."

That's no good, I didn't gather this scenario from your thread. I would do a compression check, check the oil, check your vacuum lines, clean your filter.

Yeah, check the link to the other thread I posted above.

Oil's OK, vaccuum lines would cause probs on all cylinders, filter only has 2k on it, and was new when I put it in.

Don't know how to check compression on a bike. Tips?

Buy a compression tester. Its just a gauge that reads PSI. You pull a spark plug, screw it in, take out the fuse that gives your bike spark and turn it over until the gauge stops rising. Do this on your problem cylinder. You can check all the others while you are at it if you want.