I had a question about syncing my carbs on a 93 cbr 600 with a dynojet stage 1 jet kit adjusted per instructions, yoshi exhaust, and k&n airfilter. i have had the carbs apart replaced all o-rings and am looking to sync the carbs now, i have a homemade manometer hooked up to all 4 cylinders and they pull the same air, but i dont know how much AIR each cylinder should be pulling. wasnt sure if like other screws they were a certain amount of turns. How much air should be getting past the throttle butterfly?
ANY ADVICE WILL HELP THANK YOU

 

The unfortunate answer is "As much as is needed, but not more." It all depends on how much fuel you're throwing through. Without an O2 sensor, it's REALLY hard to tell. If you smell fuel in the exhaust, then you're not letting enough air through to burn it all. If you don't smell any, but the bike is running poorly, then you're letting too much in. Tuning carbs is a lot of disassembly>tweak>reassembly>test>repeat, unless you have a dyno to get measurable, accurate results from.

Given that you're only doing a Stage 1, and you don't have a DAI system on a 93, there shouldn't be a ton of tuning necessary. If the bike is running OK and you don't smell fuel, you're probably fine. You may even have to pull back some, given that you're going to by throwing way more air through there with the new exhaust (ignore that if you're only using a slip-on).

 

Great write up on cleaning carbs. Sure wish I would have found it earlier. I've cleaned the carbs twice on my 91 600F2 and am still having a couple problems that I'm hoping someone can help me with. The first is a constant idle/low speed miss that clears up once the rpm get up around 5000. The 2nd is it sometimes will start leaking fuel out of what I'm guessing is an overflow hose while running for a minute or 2. I just had it started last night. It fired right up but sounded like it was down a cylinder and true to form cleared right up with an increase in rpm. Tried to start it today and the engine started to roll over and then hydro locked. I'm going to clean the carbs again using the write up to be sure I don't miss anything. The bike used to run great prior to setting for several months without being started. This will be the 3rd cleaning attempt and any other suggestions are welcome. I feel like I'm missing something and it's getting frustrating...
Thanks in advance for any help.

 

Your idle and low speed issue is most likely due to a dirty pilot circuit, or incorrect/inconsistent settings for the pilot fuel screws - did you pull the pilot jets and the fuel screws when you cleaned them before?

Thy hydro-lock deal is bad news, and that could potentially damage your engine - you definitely need to figure out what the source of that is.

Usually, it's a stuck float that causes a problem of that sort, but I couldn't say for sure, without working on it myself.

Good luck!

 

Thank you for the reply.
No I haven't removed any of the jets or fuel screws in the past cleanings but I will this time using the write up at the beginning of this thread. I've been trying to clean everything in place just using carb cleaner and air being afraid of getting something out of whack and making the problem worse. Truth is I lost my trusted mechanic and I'm learning as I go and am being conservitive.

My bad. To clarify: "Cleaning in place" I meant not removing any of the Jet's or fuel screws. I didn't know that the jets were just screw in or out and have been afraid of messing up an adjustment. I do remove the carbs, bowl covers, floats and needles with the rubber tips.

 

So all we are soaking would be the needle jet, main jet, and the pilot jet? Another thing, the jets were tightened all the way down. I know 2.5 turns is recommended for the pilot, what about the main/needle jet?

 

Yes, these items have orifices (holes!), so they should be soaked in a little container with some carb cleaner - the passages in the carb itself, well, obviously you could soak in a carb dip, if you had a large enough container for it, but if you did this, you would need to be certain to remove all rubber parts, unless the dip you're using is designated as safe for rubber parts... generally, these passages are just cleaned by spraying cleaner into them, letting it work for a while, and carefully blowing them out with compressed air, and repeating the process until you're confident they are clean.

The main jet, needle jet, and pilot jet are ALL to be tightened as firmly as possible, without damaging the threads or boogering up the slots for the screwdriver - the items that require "turning out" to a specific setting, are the fuel screws, which meter the pilot jet circuit. And should be set as follows, for an F2 with an OEM-type paper air filter:

2 1/8 turns for 49-state U.S. bikes
2 3/4 turns out for California bikes
2 turns out for Canadian bikes

These screws should also be removed when cleaning the carbs, but be cautious not to lose the small spring, washer, and O-Ring that goes on each screw, and make a note of the order, for reassembly.

Good luck!

 

All the jets were preboogered. (

 

Well, we can't hold that against you!

If the slots are so "jacked up" that you can't get them plenty tight without destroying them, or possibly making it impossible to get them off again, you can always replace them... main jets are $4 to $5 each, pilots are about $17 to $20, and needle jet (holders) are $12 to $15.

If they are rough, and you use them, and end up taking any shavings of brass off when tightening them up, be sure to watch for that, and get those shavings blown out of there, so they don't get sucked into the motor.

 

Hi guys,
I just started this process on my 2000 F4. On the following picture, I too the pieces labeled 1, 2, and 3 out and they are currently soaking in a bucket of carb. cleaner. They are copper-colored in the picture, but mine are so bad that the copper has a really dark/black color to it at the moment.
I have a couple of questions regarding one of the copper orifices that is not numbered on the image. I have added a blue arrow to it, and labeled it 4. It is to the left of jets numbered 1, and 3.

- Can this be removed? if So, how?
-If I insert a fishing line, or thin paperclip to clean out this area, where does the perforation lead (so I can confirm it is no longer obstructed?
-If it needs to be replaced, what is the name of this piece (labeled #4 on the diagram)?
-If the jets are clean, but do not go back to their original color (copper), should they need to be changed?

Thanks for your input/help.

-Nelson


Thanks for the guidance.