A fix for a stuttering/hesitating engine
 

Hello All,

When I first bought my 2001 CBR 600 F Sport model about a year ago, it quickly developed a bad stutter at low RPM's. The bike would behave as it if was being starved of fuel like if you have ever run out of fuel on a ride out :P Strangely, the issue only occurred below 3000 RPM, which had me rather stumped. It also idled very well and once over 3000RPM, it had plenty of power. I read every forum post I could find on the internet to get an idea of what it might be. I thought it could have been a faulty fuel injection system, faulty spark plugs, faulty coil sticks, dirty fuel filter, air filter etc etc. I decided to go with changing the spark plugs in case it was that simple. On taking the bike apart, when I pulled the first coil stick out, there was a large crack down the insulation which was an immediate red flag. So when taking out the next three, I was looking for the same thing. All the other coil sticks were fine to my relief. So I put some new iridium spark plugs into her (£50) as well as new oil, oil filter and ordered a new coil stick from ebay for £8. I got the bike reassembled and got out for a run. To my relief and delight, the problem was totally cured. So it turned out to be a broken coil stick. I hope this helps someone because I didn't read any forum posts on the internet that even suggested bad coils.

Summary

• Engine stuttering at low RPM's.
• Solved by replacing a cracked coil stick.

I'm replacing my plugs soon. Will have to investigate my coils closely and see.

Thanks!

Good idea. I can't believe how short the plugs last despite being super long lasting iridium plugs. I think they are rated to do 100'000 miles! When changing the plugs, you don't need to remove the radiator like some people say. Just ram air covers, tank and airbox. It's tight but you can twist and pull the coils out. Since the end of them is flexible rubber, I bend it so I can pull it further, otherwise you will run out of space pulling them straight up.

Its WAY easier to just remove the two rad bolts and push it out of the way. You don't even need to disconnect any hoses.

I though that would be more trouble. I'll try it that way next time!

Thanks for the tips. Noticing a little stutter on my 01 sometimes at idle and at real low RPM. Can hear when it's missing....mostly between 1500-2500 RPM. Going the same route this week, and looking into new plugs first, but will keep in mind checking the coils.