Hi, I’m new to this forum. Recently I got myself a Honda CBR600F3. It’s a project bike. It was in a very weird accident only the top part of the front fairing was smashed with no damage to the forks or the sides of the bike I got it for a very good price and the bike only has 12000km (7500 miles) on the clock. Anyway here’s my problem…

It was running fine. I actually drove with it down the streets (no cops in site)
The weekend I took of the tank because I had to send it to the spray painters along with the body parts for a quote. I also took of the Exhaust canister (It had a crack so I had it gutted just behind the crack) On Monday I refitted the exhaust. I was very curious to here what it sound like know so I refitted the tank to start the bike. The bike started but it sounded like it was running on 3 cylinders. When I looked in the tank it looked almost empty. Since I didn’t have any fuel in the garage I left it last night I got some fuel and filled her up. Now she doesn’t want to start at all she only backfires every now and then. I checked the fuel pump and its definitely pumping fuel to the carbs. I checked and there’s definitely spark on all 4 cylinders.
Does anyone now what could be wrong?

 

bro I have the same problem with mine. I took off the pipe just to hear it and left it over night. I think It is the plugs man... I just got sick of my bike and went out and bought a 929RR and left my bike sitting. Check ur plugs and see if that doesn't help. It seems as if it isn't getting any fire.

 

clean ur carbs...see if the plugs r black i use really fine sand paper to refinish or clean the plug not enough to take off metal just the black nasty junk

 

I was checking and I do have spark on the plugs.
I’m worried that it might be a problem with the valves cause when I squirt some fuel by the intake it just backfires.
I’m considering cleaning the carbs but I was checking it out and they look very complicated to remove. Last night I got as far as removing the air cleaner so I could see the intake of the carbs. It looks to me like you have to remove the coils and everythingat the top to get to the carbs.

Does anyone have a suggestion on removing the carbs (easily).I haven’t got hold of a service manual yet so I’m pretty much on my own at this stage. Any help would be appreciated.

 

Your plugs are fuel fouled.Probably faulty float needles.The bike will backfire,spit flames out the carbs and act like it is going to crank.But it will not till you replace the plugs.Once you get it cranked take it out immediatly and run it all the way to redline in second and third gear several times(obviously in a safe place).Make sure you change the oil first.It is probably contaminated with gas.

 

i had the same problem when i first baught mine aswell it sounded like a buell and backfired bad i checked all the sparkplugs didnt notice anything but then i drove it down to a shop and had the place do a full tune up and now my bike runs perfect ( knock on wood) but i would take off from a green light and if the bike didnt stall on the redlight i would accelerate and it would sound like my hand was over the exaust then all of a sudden the bike would take off like crazy and come right up. the guy at the bike shop told me i was only runnning on 2 cylinders and the other 2 would kick in. also change ur fuel filter that cant be helping the situation. mine was full of sand and rust good luck

 

All of your theories sound sounds like a possibility. The only weird thing is that the bike is just standing there (I’m not driving it) because it’s not on the road yet
The one day it starts and runs well and then the next day its just dead.
From what everyone is telling me it’s probably a carb problem. I think I’ll have to do the inevitable (I really don’t want to) and that’s to strip of everything take of the carbs, strip them and clean them, clean the plugs and then try again. There’s no easy way to get around it.
Just one question do I have to strip everything of the top including the ignition coils to remove the carbs? Can anybody give me pointers? This is my first engine with downdraft carbs. My other bike is a twin with the carbs on the side. (much easier to remove)

 

This theory will turn into a fact.It is your float needles.Go ahead and order some and get new plugs.


Here is how you remove your carbs.Take your upper and lower fairings off.Remove the seat and tank.Remove the top of the airbox only and loosen the ram air boot clamps,jiggle and pull off the airbox top and filter.Now just to make sure you dont have a bad diaphram in one of the carbs,stick your finger in the carb and gently pull up on the black slide.They should all return at approx. the same speed.Do not undo the throttle cables,no need.You may have to remove the choke cable if I remember right.Also remove the crankcase vent host up underneath the top right of the box.Undo the fuel line from the carb T inlet.Remove only the necessary air and plumbing lines to allow you to flip the carbs over paying close attn. as to how they were connected.Take a long phillips screwdriver and lossen the band clamps to the motor intake not the ones to the carbs.You will have to loosen two on one side then two on the other.Jiggle back and forth and the carbs will come up and off.Immediatly stick rags or paper towels in each engine intake port as to not have something fall in and ruin your engine.Flip the carbs upside down and they should rest where you can work on them.Remove the float bowls but do not soak these in carb cleaner,it will ruin your o-rings.Next remove your main jets,the bigger ones w/a 6mm and soak.Then remove your pilots,the small ones with a flat head and let soak.You will need a guitar string or some thing to clean the pilots.They are tiny.When they are clean you should be able to see a small round hole when holding up to the light.Now we get to the float needles.On each float you will see a silver pin that retains them.Get a small magnet and hold to the side that you will see is the only they can come out.This will pull them out enough to grasp and pull the rest of the way out.Gently lift each float out and you will see the needle hanging.This is what you want to replace(yes that tiny little thing will foul more plugs than seems possible).Replace all of these with new ones.Just take your time with all of this.None of it is hard to do.Reinstall your clean jets,paying attn. on the mains that you will have two that are a larger number,its is written on the side of the mains and should be 138's.Anyway the larger go on the two inside cylinders.Reinstall you float bowls and go in reverse order.When putting the carb boots back on the intake apply some WD to the inside of the rubber boot.Make sure you have them seated on theintake properly and start rocking back and forth till they snap down.Look underneath and double check they are all the way down.Tighten the bands and hook up everything as was before.


One more thing,before you hook the fuel line back to the T get a piece of fuel hose and hook it to your tank and straight to the T bypassing the fuel pump.Open your petcock for a few seconds and let it refill the float bowls.Then disconnect and proceed.This will keep you from running your battery down while waiting for the fuel pump to refill the floatbowls.


G

 

After removing the carbs. I stripped them and cleaned them thoroughly. On putting them back The bike still wasn’t working (that’s after I discovered I had the fuel pomp was inverted ). Anyway it still wouldn’t start. I took out all the sparkplugs with engine cleaner and put them back and can U believe it the bike starts. It started a couple of times and ran ran quite well (I couldn’t drive it since my body kit was send in to be respraid)
Suddenly the bike started missing, sounding like it’s running on one cylinder. Once again I removed the sparkplugs but this time I cleaned them with carb-cleaner and a toothbrush till I could see the metal, without scratching the probes. I put them back but it was still missing. So I left it (this was on Saturday) Last night I thought I’d just give her another try… low and behold she starts first time and runs perfectly. So it must have been the plugs. My friend tells me that those plugs are very fragile and just by flooding them once U can bust them and you’ll have to replace them. I don’t know if anyone has an opinion on this?
I’ll probably replace them once the bike is on the road but they are quite expensive R105(about $15) a piece. Can anyone tell me or check in the manual what’s the standard sparkplugs this bike uses? (we get NGK plugs around here)

 

NGK cr9eh-9 and they shoud be 8 bks a pc.Dont be surprised if after you let the bike sit for a few days you cannot get it cranked and it fouls the plugs again.I hope not but while your getting plugs get float needles and be done with it.Also any fuel fouled plug can be cleaned.Bead blasting being the best way but use fine sandpaper or whatever you have to get the black soot off of them.The main thing is to let them dry out completly.Once you reinstall them be ready to get it out and ride it immediatly and burn the rest of the crud off of them.Good luck.