Okay so I had a 96 CBR 600. Second gear went bad and I found a 98 600 engine for a decent price. I swapped the engine in and had a weird misfire problem. During diagnosis I went to pull the plugs and cylinder 1 stripped out the plug. So I dropped the engine pulled the head off the 98 and installed the 96 head on the 98 bottom end. I had problems with it continuing to foul out cylinder 2 plug. So I pulled the carbs from the 96 off and the main jets were 120,138,120,120. So I proceeded to take the main jets that were the originals from my 97 blackbird and installed them 140,142,142,140. Bike seemed to run much better but had a new issue that felt like it was running out of gas. I noticed the main jets from my blackbird were a few millimeters shorter than the one out of the 96 so I took the main jets out of the 98 carbs and installed them in the 96 carb to read 135 on all 4 cylinders. The carbs have been cleaned and synched with my homemade manometer. I still have an issue that seems like the bike is running out of gas. For instance sitting at a red light and taking off the bike will take off to about 10g on the tach then start to sputter and act what seems like it is running out of gas, and continue this regardless of speed or RpMs until I come to a stop again. Then when I take off from another stop it will take off real good until about 10 on the tach again and spit and sputter until I come to a stop again. It honestly feels like the bowls aren't filling up fast enough with gas once I take off and then when I stop the pump catches up and I can go until the bowls drain again. So I tried to gravity feed and eliminate the pump, well it still has the same issue. I don't believe it is misfiring because all plugs look good when pulled and each cylinders header pipe is about same temperature. The solenoid for the PAIR system has been removed by PO on the original 96 and never had a problem before with old engine so I don't believe that's it. I am at a complete loss as what to check and I need to get this bike fixed fast because my main sewer line broke and I need to sell the bike to pay for so any help or other things to help eliminate and remedy the problem would be greatly appreciated. Also I have all the old engine parts for sale very cheap, everything from air box to the bottom end. So if anyone is interested please let me know because I will let them go CHEAP. Thanks for your help anyone and everyone!

 

I've done tons or researching on this site and can't find a similar problem or solution. I tried blowing air through the breather vent on my gas tank tonight and air passed through the larger hole on the bottom of tank but when I blew air into the smaller nipple it seemed to compress and when I removed the air nozzle it blew back out the nipple I just blew air into. Also tried removing extra air lines to nipples inbetween the carbs in case the mini black air filters were clogged and don't believe this has changed anything(they r still not hooked up because I am unsure they r neccesary and it seems like a fuel problem). I also went through and ohmed out my coils and spark plug wires and they checked out okay and reinstalled with dielectric grease just to make sure. Ohh and when pulling the plug next to main 30 amp fuse it must have got hot at one point because plug is semi melted and contacts are corroded but I cleaned up contacts and seemed to get a good connection because bike fires up and revs wonderfully without a load on it, but once it get on the road it just continually has that issue and I am at my wits end with it. I've been through the manual multiple times and still can't figure this out. Please someone help me, I am about ready to pull my hair out!
Thanks!

 

install the 98 carbs with the engine with the air screws at the correct turns and the the jetting all sorted then see what happens? may be that your carbs are screwed and need a service kit

 

When i first fired up engine with new head i had the 98 carbs on and was misfiring and running real bad. so i switched to the 96 carbs because i know those worked on the original engine. after 96 carbs were back on i changed fuel filter and started running better than changed out main jets and it stop misfiring. my question is i noticed my fuel filter stays only about 3/4 full with gas the rest is air, is this normal? what ia the factory setting for the air/fuel mixture screws on the carbs? ive been doing 2.5 turns out and synching from there but i do have a drilled air box, k&n filter, and shorty pipe (yes very loud) instead of a muffler so maybe i should be doing 3+ turns?

 

that was going to be my first suggestion, the air screws but thought most people knew the setup sorry.

i believe for a filter and pipe its 1 3/4 turns out and for a standard or standard with filter its 1 1/2 turns out so get the air screws to 1 1/2 i know a few racers with tuned engines still running at 1 1/2 turns out so is your best bet i personally run 1 3/4 turns due to having it tuned.

do the air screws on the 98 carbs first, best bet is wind them in and see how many turns if its like 1 or 1 1/2 then stick to your 96 carbs and put them at the correct settings. not enough fuel to your air

 

So yesterday i decided to try new plugs and go with the standard ngk like honda reccommends instead of the iridiums i had in it. 1,2&4 plugs looked good but 3 the plug was pretty black, so i put the nee plugs in and fired up and still had sputtering issues, will check air/fuel screwz tonight because i believe they are set at 2 1/2 turns out because that was what i thought was stock from somewhere i read on here but ive also seen some people say 1 1/2 turns out. so i will try that. unfortunately i was also playing around with fuel pump switch contacts and while doing so they fell apart and i couldnt get the spring back in correctly. luckily i ordered a new set last week and should be here today. i hope the air/fuel scree was the problem with 3 plug being black though and not my coil, and hopefully if i adjust this correctly on the carb the sputtering/ almost acting like it is going to run outta gas will also stop. btw jack, do u kbow if the air lines running from the box to the carbs with the lil black air filter boxes are required? or can these be completely removed and just let the nipples between each carb suck in air from under tank? yes i know its not as clean or cool air but will remkving.these cause issues with sputtering while riding? Thanks

 

do you mean the hoses that are connected to the ram air that go down the bike and connect to little black boxes that then lead to that silly air solenoid? i have a HRC diagram for removing the air solenoid but i did it different put some rubber pipe the same inside diameter and just cut the hose the length you need this way removes all connectors the air solenoid and those black boxes runs fine at low revs such as cruising through the paddock and obviously has no effect on top end, the air solenoid seems to be useless.

i wouldnt remove those pipes for two reasons one it will leave your ram air with two holes in it which will mean your bike will recieve a lower volume of air at speed as it will be lost via these and the second reason would be that at low speed your bike will run very diffuclty as it would be drawing air from under the tank/ starter motor area which gets hot and you would not have the air pressure.

if you want pictures or diagrams i can pm them to you

 

any updates? im having almost same issues but my cbr boggs down at 30mph. ive replaced the fuel pump fuel filter. i also noticed that all of my hoses were not connected right goin onto my air solenoid valve also there was no hose connected from the asv to the carbs. i fixed everything to do with that and now i cant get it to start. it did run for a min but only on 3cyl help!!!!

 

the air solenoid doesnt do anything after 15mph so is not part of your issue. check your tank for corrosion, clean your tubes out and your jets with compressed air and then make sure your slides fully open with the throttle.

a bit more info makes this easier to diagnose though.. can you redline in 1st ? if you keep the power on through does it bog or splutter? can you get it through the gears and ge it running at say 50mph in 6th?

also running on three check the plugs colour black is rich white is lean a light brown is good.

dam im going to write a book on carb maintenance who would buy one?