Okay I used to get 50-55 mpg with the 883 sucker II intake xieds and cycle shack slip ons then I installed short shots which lowered it to 40-45mpg then added a 1250 cc big bore kit installed and used a power vision to tune it. Which lowered it to 30mpg

I thought I was getting 35 mpg and could live with that but then did the math 70 divided by 2.3 is really like 30mpg

Anyone know how I can boost my mpg? Or something that can be causing such poor mpg.

I'm thinking when I installed the short shots I could have done something wrong to cause a gas leak.

 

I don't fully understand your question.

Are you saying before you got 50-55 on the highway and....
now with a 1250 kit and Short Shots you get 30 highway?

50 on highway is normal / 30 on highway is not normal.
(Assuming your riding, throttle, speed habits remained the same)
(30 in town could be considered normal)

That's my confusion.

Anyway, fuel leak is possible, yet I would think you would smell fumes and deduce this fairly quickly. Leaky injector, loose fuel line.

Exhaust leak is possible, did you use new gaskets? Should be tested, yet I don't think that would account for a 20 mile per gallon difference.

Might as well confirm there is no intake leak at the throttle body. Backfiring? Starter fluid sprayed onto outside will raise rpm if there is a leak as one test.

IMO more than likely your Power Vision Tuner needs to be re-set up.

Not sure what other systems of the bike you have touched in your modding.

Another co-member may have some better advice, yet I'd bet its the Power Vision setup.

Good hunting.

 

I previously got 50-55 mpg when my big was a 883. With cycle shackles slip ons big sucker II intake and xieds


Now I have short shots power vision tuner big sucker II and hammer 1250 big bore kit


I get 30 mpg mixed riding there is back firing when engine braking / I lay off the throttle.

I reused the old gaskets because I messed up the new ones trying to install them and the old ones were all I had left to use.

Yes after the big bore kit and short shots mixed mpg is 30 it seems regardless if I do highway or city driving gas mileage is the same.

I asked dyno jet to send me a tune for better mpg and I think I got 2 mpg better with it so before I was getting 28 mpg mixed.

 

Start with the new gaskets and go from there to your tuner.

 

I'd agree all new intake and exhaust gaskets to be sure that's not an issue then a dyno tune.
Your always going to have lower MPG with more displacement, and of course now that you have more power and sound it's hard not to use it so don't expect to get anywhere near the 50 range again but high 30's/low 40's should be possible if your easy on the throttle.

 

The "canned" MAP that was loaded onto my PV by Fuel♧Moto, seemed to drop my MPG down a little more than expected, from around 48 to 42.

48 MPG may seem less than average, as some report 50+ MPG, but I can't see how this is possible, at least not the way I ride, as I'm always hammering the throttle.

Anyway, I didn't do anything about what I thought to be crappy mileage for a while and just let it ride, until mileage indicated that new spark plugs were suggested (they DID appear to indicate a rich condition but were not worn out by any means), so I gap'd and installed new ones and ran an autotune basic session, and like DUH, the bike was running better. I didn't bother to check mileage, as it seemed a moot point at the time as were checking the plugs for color (I havn't ridden much since then but will check them).

So I'd suggest that the first thing you do is pull your plugs and check each for color up against the examples in the chart below, which may indicate a rich fuel condition (other charts are available with many more possible spark plug conditions, but that isn't warranted here):



...and clean or change/gap them (type 6R12, with 0.038" - 0.043" gap, unless suggested otherwise by Hammer) if need be, then I'd be hookin' the PV up and running the bike through its paces with an auto tune basic session, flash tune the new MAP, and check your mileage, and it'll probably have improved, along with the addition of a little more zippier throttle response. After I did the above I noticed a tiny improvement...I mean it wasn't like magically adding 367cc's, but the engine was running smoother with just a touch quicker acceleration, so sayith my seat-of-the-pants dynamometer

Best wishes and please ride safe.

=8^)

 

Also are you sure that you didn't damage your o2 sensors during the exhaust swap? The damage should be obvious, nothing microscopic. Make sure u didn't damage one of the wires on them too. New exhaust gaskets are extremely important because those o2 sensors measure your air:fuel:1 ratio. Meaning typically you have 1 part air, 14.7 parts fuel. If an exhaust gasket is damaged and your o2 sensors now think u have more air coming from the engine, when in fact it's just coming from the open air, it's going to start telling the computer to dump even more fuel into the mix to bring your AFR back to 14.7:1

 

This is what I was told when I inquired about MPG from hammer performance

 

Your bike was running lean with the XIEDs. Tweak your new tuner and the mileage should go up. Remember winter blend fuels give shiity mileage.

 

I did but got a new one installed. The website I purchased it from said it was for my year make and model bike but is longer than the original o2 sensor but still the same thread pitch.