odd running like a misfire

steven_191 · Nearly there... Joined: 31 May 2009 Karma :

Its a 99 Honda hornet. When idling ever now and then it will miss a beat like unplugging a spark plug for a split second. But otherwise runs fine. I'm thinking of checking the spark plugs and gaps. Not sure what else it could be. Fueling should be fine as I stripped and checked the carbs recently.
To be honest this occured after the followig were done, new plugs, strip carbs, set up idle mixture screws as per manual, check valve clearences and the cam slipped so I took the cams out and reset the timing, timing has been checked and is ok.

I wondered if when the cam slipped a tooth it damaged a valve but compression is good and timing is correct and it runs fine all through the rev range. Just this odd stutter when idling. I'm thinking the spark isn't sparking enough or the fueling at idle is off. Maybe on one cylinder. Ill try to get a video later. Any ideas though?

pdg · World Chat Champion Joined: 15 Sep 2012 Karma :

The idle mixture screw setting in the manual is a starting point.

Because tolerance.

It's a midway point to get the thing running before setting it up properly (I would say 'before tuning' but nobody seems to understand there are different sorts of tuning, not just 'race').......
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steven_191 · Nearly there... Joined: 31 May 2009 Karma :

I intended to get the carbs balanced and tuned after the reset strip down. I had an issue before which is now sorted but I don't want to take it to be set up if there's another issue. They won't like that.
If its fuelling however their job is to sort that lol. The tuning seemed too lean to me when I was taking it apart. Especially one cylinder which was hardly a turn out from closed.

pdg · World Chat Champion Joined: 15 Sep 2012 Karma :

Until the carbs are balanced and then set up properly you won't be able to accurately diagnose any other problems anyway.

It's entirely possible that the 'lean' cylinder was correct - the screws and holes aren't always exactly the same and completely perfect, that's why you can move them.

If you had the ability to strip and rebuild the carbs, why not look into balancing them yourself? The tools required are pretty cheap and it's quite a simple job.
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Any and all advice given should not be followed - if you have to ask it means you don't know so get a man in to do it for you.

steven_191 · Nearly there... Joined: 31 May 2009 Karma :

I did do a basic balance which definitely made the bike smoother after it was all back together. I would still rather have that done properly. Been quoted £60 for a balance and mixture set up. Not rejetting or cleaning etc but that sounds ok to me.

steven_191 · Nearly there... Joined: 31 May 2009 Karma :

I just checked the plugs. See the pic below. Looks ok to me. Maybe a bit lean? The plugs are less than 100miles old. I found that the airbox rubbers that fix to the carbs are splitting away from the plastic box. Will have to replace or get some rubber cement for that as it may be pulling in unfiltered air. Not a problem as such but it might cause inconsistency if it heats up and expands or something.

Also twiddled with the mixture screws a bit and although it has made the idling a bit more lumpy it also now doesn't seem to be doing the cutting out thing. So hopefully the issue is just a bit of tuning.

New plugs on the left, old plugs on the right

https://i1112.photobucket.com/albums/k493/steven_191/Hornet/IMAG1200_zps5w5ldtje.jpg

pdg · World Chat Champion Joined: 15 Sep 2012 Karma :

Possibly just a shade on the lean side - depends on how long those plugs have been in, how fast and hard the engine has been run etc. If it's just been idled and revved a bit then reading the plugs won't tell you much (unless they are soaked in oil or bright white/burnt).

if the connectors twixt carb and airbox are split then yes, you'll get a bit of unfiltered air but that won't affect the running - what will affect it is the change in airflow/depression.

Get those rubbers sorted before spending any money on tuning because if you fix them afterwards, it'll probably need retuning. Even wrapping them up in tape will 'do the job' as a temp fix and seal it up so as not to affect the running.

Also, if you haven't already - put a new air filter in before tuning. You want to start from a point you can reproduce by conducting a service...
____________________
Any and all advice given should not be followed - if you have to ask it means you don't know so get a man in to do it for you.