I just purchased a 1992 CBR 600 from a guy and he claimed that he drove it to work multiple times this year and that the only problem with it was that the carbs need cleaned. It ran really rough and rich when I first got it so I took everything apart and cleaned the carbs perfectly. It runs way better now and revs all the way up while in neutral. However, when I try to ride the bike, it will only rev between 3-4k and just doesn't want to rev any higher. I have read multiple forums and have not found out anything to help me yet thus far. If you have any ideas as to what the problem could be, please let me know!! Thanks!

 

We need a little more info.. like how did you clean the carbs?whats the current set up? Carbs all stock or are they jetted?? What kind of air fillter and exhaust?

 

I cleaned the carbs by putting them into a gallon of carb cleaner and stirring things up every 10 mins for an hour each carb. I then sprayed carb cleaner and compressed air through each jet to make sure it was thoroughly clean. I believe the carbs are all stock and I think the air filter is also stock. It has the stock headers on it and I removed the FMF muffler that was on it because it had been cut to slip onto the stock muffler spot. Hope this info helps

 

I'm going to take a wild guess here. Even if one of your carbs was still a bit dirty, the bike would probably rev past 4k. It's usually the small/idle jets and such that clog. It usually doesn't affect the higher rpm. And I doubt all 4 are still dirty.

So I'm guessing that you have a vacuum leak going to your slide diaphragms. It sounds like you pulled all 4 carbs apart and dipped them separately, is this true? If this is the case, then I'm guessing that you didn't get all the vacuum tee's between the carbs back together correctly or an oring is missing. Or your main vacuum line to the carbs isn't hooked up. If the slides aren't working and opening, that would cause the bike not to rev into the higher rpms under load. In neutral under no load, it will still rev up because you aren't really open the carbs that much.

So basically check that you hooked the lines to the carbs back up correctly.

 

When I cleaned the carbs I made sure to check all of the jets and the little holes in them to make sure nothing was in there. Light passed through all of them and when there was a time that there was still a little gunk in there, I threw it back into the carb cleaner and sprayed it again to make sure nothing was in there. What are the slide diaphragms? I kept the carbs together because a dealership and a buddy of mine told me to not break them apart individually. Also where is the main vacuum line? I have one connected from the carbs to the petcock.




Another thing I forgot to add on my initial post is that sometimes in first gear it'll hit that spot where it doesn't rev up anymore, and then it will rev higher. This doesn't happen in second though. just stays between 3-4k.

 

Slide diaphragms are at the top of the pic under the black caps on the top of the carbs. I'm kind of going from memory here, I'm thinking now, those hoses between the carbs are vent hoses, not vacuum. It's been a while since I've worked on my carbs. Maybe open up the tops of the carbs and make sure the slides and diaphragms are good. If you soaked them, there may still be cleaner in the diaphragms.