Loss of top end power FZS 600

[Pike]

In the past couple of months I've noticed a loss of top end power, instead of the power increasing rapidly after 7/8k RPM, it seems to pretty much make the same power from 8k all the way to 12k.

Bike has about 25,000 miles and has been serviced regularly with oil. Has not had valve clearance checked, I will have to do it soon.

Chain and sprockets are just a few months old. Had correct (iridium, not that it really makes a difference) spark plugs 12 months ago. Clutch isn't slipping. I haven't checked compression recently.

I'm thinking of putting in a new air filter (K&N?) and cleaning the carbs out. Carbs could do with a balance but that can't be it.

Does anyone have any ideas?

[Bretty]

The first thing I would look at is the air filter.

I wouldn't bother cleaning the carbs unless it's noticeably running lumpy. Even then I would try redex first (£3 in b&q)

Mine has been slowly losing top end, and almost everything else I am on top of except for the air filter. I have a k&n filter which is washable. I'm pretty sure cleaning it will sort it out.

Does it continue to run on all 4 cylinders and sound and run the same, other than the lack of power?
Is the lack of power regardless of throttle position? i.e. Does it pull when you back off on the throttle, and bog down on full throttle?

[unfazed]

Yep, air filter would be the first thing to check 

[Pike]

I have been using redex every few months (last a few weeks ago, but not much was left in the bottle).

It's running on 4 cylinders, and does not depend on throttle positioning, it does rev a bit slower at WOT, that could be lack of air flow though!

I'll look into getting a new filter, does K&N provide any gains at all?

[Carter]

A quick blat up the road with the air filter out may help tell if that's the problem. Check for loose bits and bobs in the airbox before you set off though.

[darrsi]

I have been using redex every few months (last a few weeks ago, but not much was left in the bottle).

It's running on 4 cylinders, and does not depend on throttle positioning, it does rev a bit slower at WOT, that could be lack of air flow though!

I'll look into getting a new filter, does K&N provide any gains at all?

You don't gain power, but you will notice a much sharper throttle response, and the bike will feel zippier, it will generally feel a whole lot better, even more so if your filter is clogged up.
If you're considering balancing the carbs then everything else must be functioning properly first, especially having a clear air filter, otherwise you'll get a false reading and the bike won't behave right. Bike needsto be at running temperature, and the TPS checked before and after balancing.
Takes a bit of time to get it right if you have a go yourself, but the results are certainly worth it.