Spark plugs are looking like....

[mr jamez]

If they are old then carbon will build up as they will probably not burn the mixture properley. Shove in the new ones, then do a plug chop after a few proper rides, if they look like the old ones in that space of then there is obviously something not quite right on the bike.

Edit: oh great, my reply appeared before the original post Stupid clock or something.

[mr.z]

....This

https://homepages.nildram.co.uk/~noriba74/images/bike/dry.jpg

[STUNTMAN2000]

Sounds like you need a new set of plugs and get your carbs balanced. (You need a guage for this or let your bikeshop do it)

Usually around £10 per carb so a bank of 4 would be around £40.
Not from a main dealer though....you will pay through the teeth.

[stinkwheel]

There is also the old fashioned way of balancing slide carbs. It is nowhere near as accurate as using vaccuum guages but works reasonably well. I am not sure about CV carbs, they are different and this probably wouldn't work for them since the throttle valve doesn't move up unless the engine is running. Perhaps you could push them up to see where the fully open position is?

First note the position of both the tickover and cable adjuster screws so you can put it back how it was if things go wrong.

You need to be able to look into the back of the carbs to do this (a dental mirror is handy)

With the throttle closed have a look at the gap under the throttle valve skirt. Select a drill bit which is roughly the same size as the gap and, using the drill as a feeler guage, adjust both tickover screws so the gap is exactly the same on both carbs.

Now select a bigger object to use as a feeler to correspond roughly with the gap when the throttle is open by a certain amount (maybe 1/4 of the travel). With the throttle held in this position, set both gaps to fit your feeler using the throttle cable adjusters.

Your carbs are now pretty much balanced, but not necessarily set-up right. Close the throttle again and adjust the cable adjusters so there is a small amount of slack on the cable. It is important you adjust both screws by exactly the same amount. Now fire up the bike and adjust the tickover to the correct speed by progressivley adjusting the tickover screws by equal amounts.

Job done. If it is running worse, put it back how it was and call me a useless wanker.

This way makes no allowances for individual variations between the two carbs due to manufacturing tolerances and wear and is so quite 'rough and ready' but if they are way out, it is helpful and certainly cheap.

As you have probably worked out, the important thing is that the throttle valves are both in exactly the same position at the fully open and fully closed positions, you may be able to work out some way of doing this with CV carbs.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.