My riding partner had the same problem. He changed out the pcv and hasn't had a problem since.

 

So I have been doing some research and I have found that people were having this problem too. My injectors went out and my battery crapped the bed too. From what I read, people have changed out the TPS and it fixed the problem. They said their bikes didn't throw a code either.

 

Oh, I changed my plugs out for the SE plugs and wires

 

How much did this help with your mileage issue

 

Tenths of a mile. Not enough to have been the problem. I recently took off my PCV, and rode a few tanks and I'm averaging a smidge over 37 now. I am trying to work with Keith at FM to try to find a solution. I'm wanting to see what happens with a new PCV so that I can get my power back.

 

Im having this problem, have been for a while but its getting worse, ive changed fuel filter and plugs cleaned air filter. What else can i check?

 

Hello everyone ! I posted a few weeks ago about my 17 Street glide making some weird and what seemed to be metallic noises and then loss of power around 60mph when ya give her a bit more to like pass a car .. Anyway it ended up being a rear blown head gasket .. First time I've ever heard a head gasket make that type of noise but its my first M8 motor .
So under warranty and the dealer where i bought my girl at and have had some bad experiences with (dealer) took her right in and 2 days later in time for us to do our road trip vacation i got her back and i got her back in perfect condition not a bolt screw cover nothing was out of wack or missing and she was clean and ready to go...
I was very impressed with this so Thank you Eagles nest of Lathrop Ca.
BUT now my fuel mileage has gone down terribly . Before this repair i was getting 200 mpt if not 228 per tank but now i'm lucky to get 160 mpt (miles per tank) I've not changed anything .... wait i did change the mufflers from 4" Vance & Hines to 4.5" S&S slipons... well anyway i just find it hard to believe there would be that much of a difference from 4" V&H slip ons to 4.5" S&S slip ons .. Oh and while at the dealer they did a test (check) on this sumping issue that's going on and my girl was good no issues...
So does anyone have any ideas or should i take it back to the dealer and ask them to check it out, I just hate like hell not having my girl in my eye sight... LOL. she's got fresh plugs and K&N air filter ,fresh amsoil , K&P oil filter, fresh primary oil, fresh transoil and i talk dirty to her every night ...she loves the pillow talk...LMAO....

 

All of this might not be engine at all, but dragging brakes. Get each wheel off the ground and spin it by hand. How much resistance is there? Will it coast, or stop almost immediately? Low tire pressure also increases rolling resistance and causes a gas mileage penalty Do the "free checks" before dumping money into spark plugs, wires, fuel filters, air filters, throttle motors and the like. If you have enough brake drag to cause you to run in the power enrichment range most of the time, that could also be causing the sooty plugs and exhaust.