Hi,
I've been tracking the fuel efficency of my 90 cbr, which I've been riden for about two weeks now. I am getting 25-27 mpg, riding in the city, witbh some highways. I think this is a terrible efficiency, and although I still need to sync the carbs and probably play a bit more with the setup, I am wondering what kind of number do you guys get.

 

Should at least be getting 35 to 45 ............ 35 giving it the whip
45 just cruising along

 

My '87 gets 41 to 45mpg.

 

Then, in your oppinion, what could be the major cause of so much fuel consumption? spark plugs are new, I cleanned the carbs and set the pilots 3 1/2 turns. The bike was re-jetted by PO, but I am not sure to which size. It also has a Vance & Hines pipe.
I am planning to eventually do a carb sync and valves adjustment. Do you think any of these two things could be issue, or that is more related to the re-jetting of the carbs?

 

timing, valves & sync ....all 3

Yeah if the jets were changed .....that would impact mpg

Sprocket sizes ????

Stock will give you stock mpg ....... anything else will change it up or down depending

My 90 has an 18/44 on it and if I try hard I can get 48/49 mpg cruising the highway

 

I didn't thought about the sprokets. I will check that later. What exactly do you mean with timing?

 

I am not sure how to check the timing on these bikes, but on a car you check it by connecting a timing light to the #1 spark plug and the light illuminates every time #1 spak plug fires, and you aim the light at the crank case to see if it is aligned with the timing mark on the crank case. It is adjusted by moving the distibuter left and right(advanced and retarded). Now you said that you need to sync your carbs. When you swing by my place one weekend we can do a good bench sync to see if that will help ya. I still havent gotten mine synced yet, but the bench sync and a good cleaning of the carbs helped alot!. I can pull your carbs and check em for ya in no time flat.

 

Yeah man, we got to get together soon. I am wondering how are we gonna do the bench sync. Did you finally build a manometer? I am sure my carbs are clean because that is the last thing I did. How much time do you think will take me to adjust the valves?

 

I've got a K&N airfilter, rejetted carbs and a Vance & Hines exhaust. With everything else stock (sprockets , ect) I get between 35 and 38 MPG. I am pretty hard on the throttle and don't seem to get much better mileage. The carb sync helps on power and throtle response but i didn't notice better mileage. Everything listed should be normal maintinance on any new to you bike anyway. you should download the manual Workshop Manuals - CBR Forum - Enthusiast forums for Honda CBR Owners

 

Jajgarica Bench sync only sets the valves to the #3 so they open together at the same time, using a manometer is to get a more accurate adjustment as each carb works slightly different. And no I didnt build one yet, still on the to do list. Doing the valve adjust would have been faster if i didnt throw out my back in the process. I think a good 3-4 hours total from valve adjust to checking your carbs and putting all the fairings back on. But the thing with a valve adjust is that we need to do it on a cold motor. So we would need to add soem time to that if you rode your bike up to my place. It should go faster with you working on the valves while I check your carbs.

Like tobiahr said, doing the sync will only help with throttle response, it may help a lil with mpg, but not much. Might reduce it as you will want to snap the throtle more LOL

Also what does your bike have? Ie exhaust, jets, ect...