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Yes, I'm running 15/36 gearing now. I wish I could go taller.
Well, if your limiting factor is finding taller sprockets, then wish no longer! PBI sprockets offers blanks and custom sprockets. In the 520 size, the blank aluminum sprockets are available down to 32 teeth. If you select the custom aluminum option you can go down to 25 teeth!


https://shop.pbisprockets.com/category.sc?categoryId=56


I just broke 60 mpg in my 4 cylinder CBR 250R. That tank included a whole lot of 17,000 RPM, and sudden braking trying to P&G cause my older brother in front of me refuses to use the brakes, instead using engine braking. I got a more aerodynamic fender off of the OG CBR 250 Four, which I will install soon. I also got a small oil pan heater for my little screamer.





 

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I'm averaging between 72 to 78 mpg on mine in Santa Fe, NM at 7000 to 10,000 ft elevation.
Daily work commuter on weekdays and plenty of aggressive (to me) riding in the twisty hilly roads for fun.
It makes me happy for the cheap thrills!
 

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Aero front fender installed, unfortunately it was not the bolt on modification I thought it would be. It did require cutting and drilling new holes in the fender. Also, my oil pan heater wont fit on the CBR or the VFR 400. I may be able to make it fit on the radiator, will have to look into that further.

With the new fender installed, I was able to squeak in a new record tank at 60.5 MPG, breaking the previous 60.3 MPG. Most of the tank was 65+ mph pulse and glide. It has been a while since I had ridden the bike, at least two weeks, so I couldn't get a feel for how it affected coasting, but it does coast surprisingly well. It was quite windy when I was out riding, and I do think the fender made the bike slightly more sensitive to wind, but it is entirely manageable. I still have to make some brake return springs to reduce brake drag, as it is noticeable.






 

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I want got a new personal best tankfill for my CBR at the 2018 Hollister Vetter Fuel Economy Challenge with 136 mpg ( 133 miles/ 0.978 gallons ). It was the winning result for this competition. I'll post more details in the Vetter Challenge thread I started. This was done with full streamlined bodywork installed.
 

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Fuel economy does improve somewhat as you get more miles on the odometer. I'm at 8500 miles now... my fill up yesterday was 2.50 US gallons for 200 miles = 80.0 MPG. Thats with 13T front & stock rear sprockets, and an FMF Apex slip on exhaust... I don't ride the bike aiming for max fuel economy. My last few refuels showed 72 to 76 MPG, as those tanks were comprised of spirited riding on high altitude mountain roads with lots of elevation change, and working the gearbox through 7000 to 10,000 RPM's. This last tank at 80 MPG was mostly two lane country roads at fairly steady speeds, ranging between 60 and 65 MPH at 7000 to 7500 RPM in 6th gear.

I have to disagree with those who suggest that an aftermarket exhaust automatically reduces fuel economy. Getting decent MPG's depends far more on how the bike is ridden, and IMO running this engine at low RPM's (well below where it makes good power) doesn't make for better fuel economy. From what I've been reading in the various "CBR Fuel Economy" threads, it's become fairly clear that low RPM operation (under 5000 RPM) is not where better MPG's are at.
Thats interesting, I have a CB300F and I find that I have been upshifting at 4000 rpm if I do it "by ear".

I am a new rider but I feel that upshifitng at 5000 or 6000 rpm sounds like I am putting too much stress on the engine.

I also drive a stickshift car (a subcompact) and I upshift at 2500 - 3000 rpm on my little car also based on "what sounds right".

But I will go by what you veterans say, since the whole point at the end is to get the best fuel numbers.
 

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It only burns fuel when it goes pop. And lower rpm's produce less power, so your throttle opening is much greater, which reduces engine vacuum pumping losses for greater efficiency. There is a nice intake resonance tuned torque bump at 3,700-4,200 for riding through town. Coast the second half of the street length to the next stop sign. You waste gas every time you touch the brakes. My economy was down a bit this year after changing the rear pads. Plus it was much cooler this year. 115 mpgUS last year with the Michelins. Only 106 this year.
 

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Thats interesting, I have a CB300F and I find that I have been upshifting at 4000 rpm if I do it "by ear".

I am a new rider but I feel that upshifitng at 5000 or 6000 rpm sounds like I am putting too much stress on the engine.

I also drive a stickshift car (a subcompact) and I upshift at 2500 - 3000 rpm on my little car also based on "what sounds right".

But I will go by what you veterans say, since the whole point at the end is to get the best fuel numbers.
Really you're not. Unless you are bumping off the rev limiter, you are not even close tp the mechanical limits of the engine - as long as everything is properly adjusted and your oil is good and at the proper level.

Keeping the revs low is best for economy for the most part (sendler is the eco king), but don't sweat the revs.

One downside to consistent low revs, with any engine but especially the CBR, is the build-up of deposits in the combustion chamber. Revving the engine helps to move deposits out of the engine. We have heard stories here about member that are running the CBR gently, and end up with detonation damage and burned valves. That's typical of a collection of deposits in the chamber.

Some of the issues could be caused by poor fuel quality and a lack of adequate detergents. One thing that I feel is a good idea for any engine is running a strong fuel system cleaner like Chevron Techron Concentrate (1oz per gal) at least one per season. Techron will remove deposits from the intake valves and combustion chamber as well as clean the injector.

I run it every spring in all my vehicles.
 

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56,000 miles on my 2011. Half of it coasting with the clutch in. No issues with engine longevity.
Good to hear, but not everyone has been so lucky with the CBR though.

It's possible some of the issue are related to use of poor quality gas with minimal detergents.
 

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Those aren't the ones I'm thinking of, and none were the "oil filter in backwards" failures either.

The ones I'm thinking about were burned valves and damage to the piston from detonation. There was never a conclusive answer, but based on how the owners described their riding style it fit that it could have been caused by a build-up of deposits.

Running a fuel system cleaner annually is just basic maintenance, but it may have additional benefits in this case.
 

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One thing that I feel is a good idea for any engine is running a strong fuel system cleaner like Chevron Techron Concentrate (1oz per gal) at least one per season. Techron will remove deposits from the intake valves and combustion chamber as well as clean the injector.

I run it every spring in all my vehicles.
You recommended that stuff so often you should become a sales person for them. :grin2:
 
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