Engine Flat Spot

davidimurray · Nitrous Nuisance Joined: 04 Jul 2006 Karma :

My bike seems to have developed an interesting 'flat spot' in the revs. If i rdie up to around 5000RPM, hold it steady then open the throttle it just doesn't accelerate. The engine tries to pull, you can hear the exhaust note change, but it just won't go.

Does it in all gears. If I start below 5000 RPM and accelerate through that range it's fine.

I haven't got around to looking at it yet, in the meantime any ideas what it could be? The bike has had a K&N fitted for a few months now but it never used to be like this.

Cheers

Dave

TheShaggyDA · Repost Police Joined: 14 Jun 2004 Karma :

What bike do you have? How old is it?

Possibly a slipping clutch - my Enfield would happily accelerate (I use the term very loosely) up to top speed in one go, but if I were cruising and then just opened the throttle it would have to be coaxed up. Once the clutch cable settled in it was better, and it disappeared once I put heavier springs in.
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davidimurray · Nitrous Nuisance Joined: 04 Jul 2006 Karma :

Hi

It's a 2002 Kawasaki ER5 - it had a new clutch about 2000 miles ago and the revs don't actually go up when I nail it.

One other thought, i've been using the car a bit for work so it's taken me 4 weeks to get through a tank of fuel - could it be going off?

Cheers

Dave

Diggs · World Chat Champion Joined: 03 Apr 2007 Karma :

Check the plugs - old plugs cam cause those symptoms too...
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davidimurray · Nitrous Nuisance Joined: 04 Jul 2006 Karma :

The plugs were changed about a month and a half ago at the same time the carbs were balanced.

theguitardoct... · L Plate Warrior Joined: 10 Apr 2007 Karma :

I had a Kwak that behaved exactly like this, and it was down to a tube that had been "re-connected" during a service...basically a tube got stuck onto the moisture outlet on the airbox and it created a vacuum which stopped it getting above 5000rpm. I took the pipe off after I removed the tank, and lo and behold she revved freely again...check they didn't do this amongst the other problems...

Failing this, try some carb/imjector cleaner type additive and maybe change out the fuel filter as that may be restrictng flow when you nail it.....