Plug gap is not a good way to deal with lean condition. You need to do something to the fueling issue to have any idea what's going on. Fixing the exhaust was important but since it had no effect you'll have to look at carb tuning. You could try next size mains, even if it messes up the rest of the range at least you'll know.

As far as the electrical issues can't help much if modified. Is there a switch on the fan?

 

Sorted the whole loom out today.. Put the wiring under the tank, nice and neat! .. The PO hard wired a fan to the switch. Now when the autofan came on it blew the main fuse and the bike was taking power from the hot wire to the fan! Total disaster! I isolated the fan and switch from the rest of the loom so I have a manual fan that can't hurt the rest of the bike. When my temp gauge arrives I will drain the system, install the aftermarket sensor and a new auto sensor together with a switch for auto/manual fan mode, then fill it with proper coolant and not the water that's in it!

Yes I think it's carb tuning time.. I will up the needles and see if it helps at all so I know in going in the right direction then order some mains

 

I put 3 little washers under the needles and took it for a quick spin. It actually felt a little stronger in the low rpms, say accelerating normally in the flow of traffic, and then when you punch it to 3/4 throttle or even roll it on gently it still has the damn flat spot.. The strange thing is if I get up to say 30mph in 2nd gear and down shift to first to get it over the flat spot then pin it, it takes off like a rocket with no missing or stuttering... Starting to suspect maybe an electrical issue.. As I hit the flat spot with a gentle roll on or WOT in one go.. It starts and idles perfect and round town its smooth as a Honda should be.. What do you think?

Thanks!

Edit: if you rev it to redline in neutral when warmed up, it will get to red line but u hear it stutter half way up! And u don't need full throttle to rev in neutral.. If I get it over the stutter/flat spot then keep it revving and annoying my street with the noise its perfect and even pops out a little black smoke so I'm sure its not dangerously lean...

 

This type of tuning problem is annoying as hell. Did the flat spot move after you put the washers in? The black smoke on decel of the engine likely is from the low end of the fuel delivery being slightly richer with the higher needle position. I wouldn't talk myself into believing it's ok (not lean) until I knew for sure. You really should find someone with an O2 sniffer.

Electrical? Why would you think that? What could cause a consistent issue in the same spot that would be electrical? I can't think of anything. Most electrical problems wouldn't be consistent.

 

Why don't you do a quick test by Duct Taping some of the holes?

 

The flat spot didn't move at all really.. What is kinda wierd is that I just went into the garage and started it up.. Engine was still warm to the touch.. Gave it a rev and same problem.. Then out of anger revved and bounced it off the limiter for a second.. Then next rev was perfect no flat spot!! When it stops raining I'll take it out for a test.. I'll try and tape up more holes if the issue is still apparent. I though electrical as it always happens in that one spot and at any throttle opening.

 

Finally went out for a ride and let it warm up properly.. Once up to temp the flat spot was still there and couldn't get past it without down shifting to bring up the revs, also low end fueling was a mess when hot.. So I'll remove the washers and put bigger main jets. I've got a "sport" exhaust which is very free flowing and a drilled air box ( might as well get a bit more bhp if possible eh).. How many sizes up should I go? I'm at sea level in a warm country. Also are these correct? http://m.ebay.co.uk/itm/Genuine-Keihin-CVK-PE-PZ-Carburetor-Main-Jet-short-8mm-99101-393-70-190-/142228970740?nav=SEARCH&varId=441296341067

Thanks for your wisdom!

 

Get on a dyno with an O2 sniffer. You can chase this forever and never have a clue what's going on. Sorry. In cases like this that's the only way to do it.

 

agreed its gonna be easier to go on dyno etc, but still need to buy jets. Im looking at either the 6sigma jet jit or individual ones. Do you know if the ones i posted from ebay are the correct ones? Cheers

 

I don't buy jets on EBay just not the best way to buy them. I use Jets are Us because they list all that are available along with all parts you might need.