I have a 1993 honda cbr 600 f2. I bought it from a guy who said he had the carb syncd before it sat in the store for 2 months. I try to start it but it will just crank over and occasional misfire. I took off the fairings and airbox. I put gas directly into the carbs and it will still just crank and misfire. Once it a while it start but just misfire and idle at 2000 with the throttle fully open for 10 seconds then die. I took off the carb and cleaned the jets and floats; nothing was stuck or dirty at all. I replaced the spark plugs, checked the spark and it all looks fine. What else could it be?

 

Sounds like to me that not all four cylinders are firing. Find out with ones aren't by feeling the exhaust pipes and feeling which ones are cold. Use a wet rag and just touch it for a split second. They should be super hot so be very VERY careful not to burn your hands. If you find out which cylinders aren't firing, take the plugs out, and plug the hole with the palm of your hand to see if you're getting ANY compression. If you feel absolutely no compression, then you have a mechanical issue with either the valves or cylinder. If you have compression, then it's your carbs. Almost 90% of the time, it's always the carburetor. Take apart the entire carb. And I mean ENTIRE carb. Take every single needle/jet out and make sure you can see light coming out of the jets clearly. Make sure you take the plungers out and see if the springs didn't go bad or the seat. Best thing to do is to soak the jets in carb cleaner for a good 30 mins and shake them. Shooting compressed air works great too. Check the diaphragms as well...for a 20 year old bike, that's what would most likely have to be replaced. Check for small holes or tears in the diaphragms. Instructions on the removal of the diaphragms can be found in the service manual.

I know this is lots of information, but take it step by step how I explained it so you can eliminate the obvious and narrow it down to the problem.

 

Did the previous owner do any work on the plugs? If so, it's possible that the wires attached to the wrong plugs...

 

well he replaced all the plugs so hopefully he knows how to put the wires back in. I'd say check the air air filter, if its a paper filter, replace. If its a cloth one clean it out with the air filter spray

 

I have taken apart the carb, cleaned the jets. I have not checked all the diaphrams yet I will do that next as well as check for compression.
It is a cloth filter I will clean that as well.

 

doublecheck firing order, and that you're getting spark at all 4 plugs. The bike will run on 3 cylinders all day, and I got mine to run on 2 briefly with 1 & 4 unplugged

Proper firing order for our bikes is 1-2-4-3. plugs 1 & 4 are run off the right side coil, plugs 2 & 3 are off the left side coil.

both coils have a 2-wire plug fromt he wiring harness - both plugs have a Black/White wire. Right side coil (1&4) should have the Yellow wire/blue stripe plugged into it. The Left side coil has the blue wire w yellow stripe.

 

Don't think its the air filter as he has removed it from the equation. Compression needs to be checked with a gauge & not your fingers. You can have bad compression & it still blow your finger out of the hole, if you can even get it in that far.
Check the routing of the plug wires to make sure they are in the correct location as adrenalnjunky stated, make sure the plugs are good & not fouled at all, & clean the carbs.

 

Misfiring randomly while succesfully cranking over to me tends to spell this. You checked for spark as well right? Just pull a single spark plug wire, jam any old spark plug in there and throw it on the frame (steel, grounded last I checked) and crank it over. You'll see if you have spark.

Firing order does sound like the culprit though!

 

Alright thank you everybody I will be working on the bike today and I will let you know how it goes. I appreciate the help.

 

I tore apart the carbs again and checked everything, it was all fine. I then checked to make sure the spark plug wires where running to the right cylinders from the correct coils, and guess what? Three of them were off. So I found the manual online and got the right order. It then started up and allowed me to rev it, then I put the gas tank back on it and it runs great now.

Thank everyone for the help.