Motorcycle Repair: Excessive Fuel Consumption, fuel consuption, heritage softail

Question
QUESTION: Hi Mike,

I have a problem with my 2002 Heritage Softail Classic FLSTC/I, and having read your answers here, I reckon you're the best guy to ask.

I have noticed a significant increase in fuel consumption. I purchased the bike in July last year and it was great. I had new tyres fitted in the October, and the problem started . Initially, the brakes were binding due to warped discs (had the tyres fitted at non-Harley place). Got that sorted, but still the same consumption, yet the wheels spin freely now. It still feels as though I need to open the throttle more than I used to.
I've heard a lot of theories on the reasons for the increase, and hope you can help me with them, even though they may seem silly:

1. The change of tyre brand (I have Continental Milestones instead of the standard Dunlops).
2. It's almost due a service and the old oil's causing some drag in the engine.
3. The bike uses more fuel in winter (remember, I had no problems in Summer, and it's rather cold in England these days!)

I hope you can help me. The Dealer's tried to help, but to no avail (they're great guys though).

Thanks in advance!

Regards,

Jerry

ANSWER: How much of a difference have you noticed?
Mike

---------- FOLLOW-UP ----------

QUESTION: Hi Mike,

Thanks for replying. Okay, it's around 30-40 miles per tank. Up to 10 miles per gallon (I'm talking UK figures here).



ANSWER: Changing the tires to a diffrerent brand might change it a little, but not that much unless you went with a different size tire than stock.
The oil wont really affect the fuel consuption.
Winter, you will us a littel more fuel, due to the cold. Colder outside temp, more fuel you use.
Dropping that much I might suppect an ignition problem. Pull your spark plugs and let me know what color they are.
Good luck and happy riding
Mike

---------- FOLLOW-UP ----------

QUESTION: Hi Mike,

I hope you're well. The plugs appear to be normal. Not black or dark, but not white either. Somewhere in between, like a light grey/bit of light brown. I had the bike diagnosted at the H-D dealer, and it came back fine (ignition seems to be okay)...so, I'm at a loss again.

Regards,

Jerry

Answer
You plugs sound fine, so that is not the problem. the only other things it could be is the rear wheel is not aligned with the trans properly, the rear belt or the primary chain is to tight, not enough air in the tires, bad wheel bearing or the brakes are binding.
Good luck and happy riding
Mike