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Old 12-29-2017, 07:14 PM   #1 (permalink)
EcoModding flying lizard
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Join Date: May 2012
Location: Georgia
Posts: 501

Cibbie - '88 Honda CBR 250R
90 day: 56.34 mpg (US)

Rarity - '06 Honda Accord EX V6
Team Honda
90 day: 41.28 mpg (US)

Baby viff - '86 Honda VFR 400R
90 day: 48.31 mpg (US)
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Cibbie-1988 CBR 250R

Most people start on small to medium engined bikes and move up from there. I started out on street bikes with a VF500, then went up to a VFR800, and back DOWN to a CBR 250R. Why? Because I love tiny engines, especially multicylinder engines! I got this bike specifically because of the sound. I saw one video of it and I was hooked.

This is the video that poisoned me.

Having had this bike for at least two years now, I figured I should start a thread for my little screamer to celebrate my first real eco mod to it, taller gearing.

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Honda says this thing revs to 18.5K. It has been said that they were optimistic and that it only revs to 17.3K. The MC22, which is the newer model with a slightly revised engine appears to rev higher, and it certainly sounds like it too.
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When I first got the bike, it was all stock. The exhaust was of course too quiet, so I put an aftermarket muffler on it. Stock, it would get around 58 mpg with how I ride it now. With the new muffler along with its reduced low end torque brought the gas mileage down to around 54 mpg. I changed the main jets up to 90s instead of 85s when the muffler was installed. The pilot jets were also richened at the time, but I have since adjusted them back to the stock setting.

At some point in ownership of the bike it had what seemed like "cylinder deactivation" problems where the bike would start to lose cylinders and power to the point where it could not maintain speed anymore. It eventually turned out to be a fuel supply problem from a kinked hose. However, before that was found out, I thought it was an ignition related problem, so I got a new ECU. The new ECU was advertised as "derestricted", yeah, it was derestricted all right. IT HAS NO REV LIMITER! Normally the bike has a rev limiter at 18.5K rpm indicated, I took the bike up to 20.5K rpm indicated looking for the new rev limiter before deciding continuing to rev higher will only result in destruction. The bike still has that ECU in it, gotta remember to swap back to stock. The pathetic thing is that despite being "derestricted", it still has the 10-14K rpm retarded ignition timing that the stock ECU has.

My non O-ring chain recently wore out(Took less than 5K miles! ), so I decided to renew my search for taller sprockets when getting the new chain. This model bike uses a 428 pitch chain, narrowing options significantly. Thankfully, my dad found a 51T rear sprocket off of the 1989-1990 VTR 250, a similar bike in other regards as well. Apparently other parts are shared between these two bikes. Stock gearing is 17T/54T, so a 51T rear sprocket results in 5.5% taller gearing.

IIRC the hole setup for the rear sprocket is 6 holes with a 150mm centerline.

Here is a gem I found featuring an MC22 and its eargasmic sound.

-Kaze o tatakaimasen-

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Best trip in v6: 50.4
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Originally Posted by MetroMPG View Post
You can lead a fashion-conscious horse to unusual-looking water...

Last edited by Daschicken; 01-12-2018 at 05:34 PM..
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