ZZR600D rough running issues

sgtcalle · Spanner Monkey Joined: 07 Sep 2011 Karma :

Hi all, I have a '90 plate 600D. I'm currently having running problems as follows:

At low RPM in first and second gear (generally when revving from idle - i.e. pulling away from lights etc) the bike loses power and bogs down. This only happens once the bike is hot, the first 5 minutes of riding is fine. At higher revs, or just cruising, the bike performs fine.

I first noticed the problem a few weeks ago, and its been getting progressively worse. The bike is used for a short 15 minute commute, so I have read there may be condensation forming in the float bowls. I have taken it out for a couple of longer 40-50 mile runs, which hasn't made an improvement (made it worse if anything).

Its just been in the garage for an MOT, and i asked them to take a look/give me their opinion on the running problem. Very occasionally, after turning the ignition nothing happens which suggests to me a dodgy connection. However i stress this happens very occasionally, and hasn't been getting any worse. The garage suggested that this could be the cause of the rough running, but i dont see how this can be the case? They also suggested that the clutch plates could do with being replaced. They're probably right, but i doubt this is related to the rough running, as with the bike in neutral and the clutch disengaged, the bike still bogs when revved from idle. Am i correct in my thinking here?

Thanks for any help.
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CBR600F '02
Manchester

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

The ignition thing is likely to be seperate.

What you are describing is rich running. I'd suggest inspecting and replacing the float needles as first port of call. They are a prime cause of grief in older bikes.
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sgtcalle · Spanner Monkey Joined: 07 Sep 2011 Karma :

Ok thanks. How difficult a job is this? Thanks
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CBR600F '02
Manchester

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

sgtcalle · Spanner Monkey Joined: 07 Sep 2011 Karma :

I took the bike into the garage as i didn't have time to do it myself, they inspected the carbs, balanced them and cleaned them. Apparently the float needles were in good shape, and the carbs generally not too bad. I also replaced the air filter. The bike is still running like a dog however.

I cant afford to pay mechanics to do anymore, they suggested the next place to look is the plug caps, as apparently they are in pretty poor shape. Does anyone have an opinion on this? Is it likely to cause the symptoms listed? Also, slightly silly question, but when installing spark plug caps, you just press them onto the plugs untill they lock do you not?

Thanks.
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CBR600F '02
Manchester

gavcarter · Could Be A Chat Bot Joined: 28 Mar 2009 Karma :

jjdugen · World Chat Champion Joined: 03 Jun 2011 Karma :

Just throwing this into the mix. Check your chokes are returning fully. These engines are really touchy if even one of the chokes is not fully home once the engine warms up a bit. The slider bar that operates the chokes can get clagged up as can the choke pistons. I spent a day trying to find that one on mine, same symptoms as you describe.

cheers.
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andys675 · World Chat Champion Joined: 08 Feb 2007 Karma :

did they have a look at the carb diaphragms?
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sgtcalle · Spanner Monkey Joined: 07 Sep 2011 Karma :

Ok thanks lads, somewhere to start i suppose! I assume the garage looked at the diaphragms, nothing specific was mentioned though. I seem to remember a thread on here where a split diaphragm was causing issues?

Also, are there standard spark plug caps i can buy? Searching for ZZR6 plug caps doesnt seem to yield many results
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CBR600F '02
Manchester