I just bought this bike about 4 weeks ago. First 3 fill ups I was getting 42-45 mpg (us gal.). The last 2 fillups I'm getting about 32-34 mpg. I changed the oil and plugs after the first low mileage fillup and didn't see any change (other than a little more power). I was planning on syncing the carbs and maybe checking the valves, any other suggestions? Should I pull the carbs first and give them a good cleaning? Any thing else I should check?

 

Check your air filter - CBR's don't like it to be dirty, lowers gas mileage
Also: You're probably riding it a bit harder as you get used to it.
Did you change the sprocketing ? That would also have an effect.....
Check your choke isn't sticky

 

I thought about the riding harder cause after the first 32mpg fillup. I made it a point to not get above 5000 rpm this last tank. I even started shifting at the manuals recomended shift points (gawd that feels weird, all I do is shift, twist, shift, twist) no real change.I hadn't thought about the filter though. I was told it was a K&N when I bought the bike, guess tonight I'll find out.

 

Good idea on the air filter, but also check to make sure the rest of the ducts are free from little critters getting in there and building a nest , plugging up your air intake. Happened to me. How is the bike running? Notice any black smoke, hesitations in the engine? if its runnning rich you should be able to see it.

 

Don't forget the simple things too, like tire pressure.

 

Running as well as the day I got it but that wasnt to long ago. I havent seen any black smoke...doesnt appear to be running rich. The plugs looked good when I changed them this weekend. I have noticed a fuel smell in the garage but wasnt sure where it was coming from other than a running vehicle being parked in there. I inspected the carbs externally when I was changing the oil and oiling the chain this weekend and didnt see any evidence of fuel leakage. I may have missed it though. Ill definitely check the air box/filter this evening and will probably service/sync the carbs this weekend. Since I just bought the bike I wanted to go through and do most of the scheduled maintenance just to make sure it got done even if the previous owner didnt do it. It just concerned me that such a drastic change occurred so quickly. I appreciate all the responses and any advice thats given, and I have a lot of respect for the members of this forum.

Idodirt: I did check the pressure and actually increased the pressure to the manufacturers recommendations. Wouldnt lower pressure hurt the mileage? I just want to make sure Im not confusing my facts as I do that quite often. Thats why I ask questions here

 

If you noticed a fuel smell, you may wish to check your tank for a fuel leak UNDERNEATH the reflective cladding on the bottom of the tank - took me ages to find mine[X(]
Also a split fuel lead will cost you mileage, but will evaporate in the heat without you being able to pinpoint it.......
Just another 2c worth

 

just a quick check...other than any damage I might do because of inexperience, should I need to buy anything for a quick cleaning of my carbs? I've pulled carbs on earlier bikes and had to replace paper gaskets on a rebuild but didn't have to replace the o ring type gaskets.

 

If during your first two fillups, most of your riding involved long rides, out of town, at fairly steady highway speeds, and the next two involved a lot of short hops around town, that could easily explain the difference. Your numbers are not out of line with the mileage I get, depending on where and how I'm riding. I wouldn't think your air filter is the culprit- they tend to go over time, not all at once.

 

I hear this is great for older Bikes

http://www.oreillyauto.com/EW3/Produ...&currentPage=0