1996 Honda CBR250RR

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Joined: Fri Feb 03, 2012 1:18 pm

1996 Honda CBR250RR

Post by motthomas » Mon Sep 29, 2014 4:20 am

Since this is the forum to post success stories, I figure its about time I post mine. :) Maybe it will help encourage others to take on a similar project.

The bike in its stock form is a 250cc I4 engine which revs to 17,000rpm (19,000rpm indicated) and makes 40bhp. It runs 30mm individual CV carbs and is a hoot to ride!

I started the project as a way to keep my mind ticking over while doing a non technical job and also because I had become interested in megasquirt conversions a few years ago and had not heard of a conversion being done on another 1990s 250cc I4 engine.

The bike currently runs and drives beautifully (albeit some rough edges that need smoothing out with further tuning). I have verified the ECU is well capable of providing ignition and fuel control at high revs and am very happy with the outcome of the project so far. Saying that, it has taken over 2 years to come to this point so it was not easily acheived. Several design changes occurred as things progressed and the finished product is not very close to what I had imagined when I started.

I have tried to keep a log of my progress on the project on my blog here: http://projectcbr250rri.blogspot.com/
And I also kept a thread on the CBR250.com forum here: http://cbr250.com/forums/project-bikes/ ... 50rri.html

As a quick overview, here is a brief summary of the configuration and components used:

- Microsquirt v3 ECU
- Throttle bodies are stock carburettors modified to accept injectors and fuel rail mountings as well as a TPS.
- Fuel pump is a 2005 ZX10R in tank pump which mounts in a modified stock CBR250RR fuel tank
- TPS is from a 2001 GSXR750
- MAP sensor is from a 2001 GSXR750. Map signal pulled from all 4 intake ports and combined before connecting to the MAP sensor
- Injectors are 2003 CBR600RR secondary injectors which flow ~168cc/min with the pressure supplied by the ZX10R fuel pump
- Crank position signal is provided by the stock trigger wheel and VR sensor
- Ignition is MS controlled using a racing 2D map extracted from a Bluefox racing CDI. It runs wasted spark through the stock coils and incorporates a seperate ignition driver unit external to the Microsquirt ECU.
- Fuel load is currently on a speed-density algorithm. I had originally planned to use Alpha-N but changed due to lack of resolution from the TPS at low throttle openings.
- The stock dash was exchanged for an aftermarket Koso RX-2N gauge as the stock clocks did not like the MS TACHOUT signal
- Tuning is being carried out using a PLX SM-AFR wideband O2 sensor

Further details, photos and videos are in the blog or the forum thread.

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Re: 1996 Honda CBR250RR

Post by R100RT » Wed Oct 01, 2014 6:02 am

Very nice work, and I imagine a real "perk up"?
I'm envious of your rpm range, also your pistons must be real small 8)
Regards, Lorne

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Joined: Sun Dec 07, 2014 6:48 am

Re: 1996 Honda CBR250RR

Post by 23030006 » Sun Dec 07, 2014 7:14 am

:D I like your Project。
Install MegaSquirt-II in 1992 YAMAHA XV250, currently a little frustration and problems。

so sad :(

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