Hi everyone,
I'm having a hell of a time trying to diagnose this very mysterious problem and all the avenues on here seem to end up with air solenoid delete (tried and no cigar) and poorly cleaned carburettors (also gone through several times, jets and passages clear). My sorry CBR600F3 '96 accelerates fine till 5,000rpm and it stutters and bogs with no power at all and as soon as it gets to 7,500rpm it clears and flies! Its consistent every time and it ruins the ride so much I just don't bother with it and it feels like its getting the better of my experience and troubleshooting.

Its had;

• New air filter (stock)
• new headers (Black Widow) and end can (Delkevic)
• new spark plugs (Champion)
• new fuel filter
• fuel lines and petcock/strainer cleaned
• new fuel pump and relay
• new reg/rec with new male/female connectors

Fuel pump is doing its thing clicking away and flows fine, in fact the plugs were black bright so it is running very rich. Air ducts are all set up correctly and clear, slides go up when you blow down the right side one.

Dammit what am i missing?? trying some new coils and leads and new NGK plugs to see if its weak spark! Battery is good and strong and charges fine with the new reg/rec and fuses all gone through!

Had enough now... any help appreciated!

Danny

 

If I recall, and it's been a while. That mid-range flat spot seemed to be an issue for most everyone who went the aftermarket Header route. I'm not much help with that as all mine are stock. Maybe someone else on here was able to get it resolved.

 

Hey idodirt, thanks for the reply buddy. These headers were supposed to be used on the F3 with no additional tweaks or tuning, as was the end can! Absolute nightmare

 

I'm surprised that they market it that way. I did notice that they (BlackWidow) don't provide any performance graphs to indicate performance compared to stock. I notice that virtually all aftermarket headers don't have the short crossover tubes between the down pipes of 1 to 2 and 3 to 4 like the stock exhausts do. Every year F2 and F3 has them. I know that the F3 incorporated the D.A.I. system. That's the part that everyone likes to eliminate. Performance tuning on a carbureted motorcycle is much more challenging than a fuel injected bike. You really need a dyno to be sure what affect the changes have, but the time involved in moving jet needles up and down or changing jets is time consuming. Changing the program map in a computer is a couple clicks of the mouse.

I feel your pain.

 

They would be a huge waste of £200 to go back to stock! I have been trying to reach people who have bought the same and nobody has replied, it was just highly suspect that it should get worse after swapping the OEM Honda headers.

Mine were full of holes and an awful attempt at welding by the flanges meant they didn’t fit properly! Really hoping this is an electrical issue and the spark strength doesn’t follow the Rev range as it should under load and that some new wires will sort this out.

a multimeter test had no reading at all from cap to cap (the bit that connects the plug) but could have been doing it wrong.. the opposite end at the coil input read within spec but very different of each other. Would this be a clue? My electrical experience is next to nil

 

@Halftonmum How to check the Ignition Coils. Make sure you're checking the leads that go to the same coil.

 

That’s amazing Thankyou! Save me going to Swansea for some newer ones tomorrow but it’ll mean back to square one!

did the test in the second picture and it didn’t come up with anything at all.. I know I did that one right

 

It can be challenging to get your meter leads onto the actual metal components of the plug wire's. You're confident you made contact with them? Also (not to question your meter skills), but did you have your meter on a high enough Ohm scale in order to read the 20,000 to 25,000 Ohms? Just making sure you realize that the first picture is 2.5 to 3.1 Ohms and that the second one is in the thousands of Ohms.

 

The probes touched metal but not the inner part where the thread goes if that makes sense…?

I have ordered another stator for £10 and have some working coils tomorrow, god I hope this works..

Have you had much experience with engine rebuilding? Fearing the worst of this isn't the fix.. it’s for the scrap yard if not! Another engine is gonna be a good few hundred and who knows what could be wrong with those too.

(edit) the stator plug is all burnt out so won’t chance it being ok! Will test it tomorrow to see for sure but it’s getting binned.

 

The stator plug being burnt is just a sign that the connections were poor and it heated up. That is common over time. That doesn't mean the Stator is bad. Replacing the Stator connector and pins would probably fix that. Checking with a meter is a good idea.

If you can post some pictures of what/how you're making the checks, that will help it make sense.