Hi, just joined (this is my 2nd post)

I have 1998 Honda CBR 900RR, and I do have a big problem with the bike.

It almost seems like it's getting flooded, sometimes it won't go pass 5k rpm, the exhaust does sound like a v8 car upon deceleration. It's impossible to drive it on freeway, I guess load in 6th gear is at 4k rpm, and it slowlly starts to die on me. When you rev it in neutral it sometimes will go to 11k rpm, but sometimes it gets stuck at 5k. When you get on it, it will accelerate nicely to 5k and then it will start backfiring.

I did clean the carbs, they weren't too dirty, but it still didn't solve the issue.

What else can I try?


P.S Where can I get temp sensor (the one that screws in by the carbs)?

 

there is a post on this very page with an identical problem to yours. You both need better cleaning techniques on your carbs cause there is a 90% chance that thats causing you grief. Cleaning the carbs doesn't really mean checking to see if they are dirty inside. It means making sure that all the jets and fuel passages are free on any debris or fuel residue buildup that could impede flow and function. A lot of people are under the impression that they can pull the carbs are spray them down with cleaner and thats the end of it. In actuality if you did not take everything removable off the carb bank and have it either hot tanked, ultrasonic cleaned, or at least soaked over night then they are not really clean and you cannot cross them off the list of potential culprits. You need to blow out all ports and passages and sync the carbs after your done or your wasting your time. Do everything mentioned above and then see where that leaves you. I would also pull your plugs and see which one looks different than the others, that will be the cylinder that is having the issue.

 

When I was cleaning carbs cylinder 3 was the dirties, and I mean everything off that cylinder. Also syncing carbs - what is that exactly. Can it be done on my own?


I read the other threads, but they didn't really seem to have the same problem I had. They had idling issues and exhaust sound, but no major power loss, not even talking about the issue where bike won't go past 5k rpm....

Thank you for your reply though

 

Alright, haven't found much explanation of syncing, but had found enough to understand that I won't be able to do it myself

 

your 5K rev issue is probably your pilot jet on one or more of the carbs being clogged. The bike will run fine with the idle circuit up to about 4K and then have issues as the needle jet and pilot circuit take over. The bike will idle fine and all but its starving for fuel on one cylinder in the midrange. Cylinder 3 is probably the one with the carb problem. If you look through each of the jets are the pin holes perfectly round? Can you see through the jets? These holes are tiny and a grain of sand can clog them. There is also the port above the jet to look at cause gummy gas and deposits can catch in there as well.

Carb syncing is the process of adjusting the vacuum on all of the carbs to match the #3 carb, which has no adjustment. To do this you need a 4 gauge set that you hook to the vac. port under the carbs. Then you idle the bike and adjust the throttle stop screws while watching the vac. gauges until they all read the same or damn close. If you are not experienced with mechanics and don't want to spend 200$ on the guage set then this is a job for the pros.

 

Carb cleaning properly and synchronization is a must!

Are spark plug gaps correct?
And if the 900rr has a TPS, that might have some fault...

 

Alright, Syncing fixed the problem. It's a day and night difference. Can't believe how much better bike runs now. Also there was some fuel in oil, so got oil changed while at it.!!!!!

 

did you end up syncing them yourself? i don't have much experience and i want to sync my carbs. should i have someone do it for me?