Power increase with a K&N?

[Adam 105th sportster]

Firstly I'm nearly out of newbie questions so thanks for your patience!

K&N air filters, I use them on my cars as they are the best IMO. I'm going to get one for the bike too. Anyone know a rough power increase figure on a 1200 & one coupled with a set of V&H slip ons.

Insurance (Bennetts) said mods that increase up to 5% are ok so I want to know if I need to inform them and how much over if any these two mods are making. Don't mind the extra on the premiums but want to be legal if I need their services.

[Reaper]

If it's just the filter then you'd be lucky to see an improvement, you have to change the restrictive back plate as well to let more air in. Then you will need some kind of fuel pack ( V&H, Power Commander etc ), it will then give you a lot more than a 5% increase. In the US they mention up to a 20bhp increase with a stage 1 ( dyno results ). I would expect a 20% increase is feasible. HTH.

[Stephen]

20bhp seems a lot to me

[grbrown]

Originally Posted by Stephen

20bhp seems a lot to me

Agreed - it would be a challenge to get that sort of improvement with what I understand to be Stage 1. However these bikes are seriously strangled as standard, so a free flowing exhaust, ditto air cleaner and appropriate carb/injection tweaks can be very worthwhile.