HONDA CRF250 RALLY OWNERS

Discussion in 'Thumpers' started by ferdiepick, Mar 18, 2017.

  1. RiderRider

    RiderRider Just ride!

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    From were did you order the ECU?
  2. Noisytim

    Noisytim Adventurer

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  3. RiderRider

    RiderRider Just ride!

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    Thanks Noisytim!

    @jonnylikesvtwins @Noisytim Please keep us up to date on your experience on this ECU change.

    I wil be interested in this change also, while keeping the airbox and exauste stock!
  4. Chrisbarnes1

    Chrisbarnes1 Been here awhile

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    Fiddling inside the exhaust can open it out a bit--but you have to get in there first, and if its all welded then its a bandsaw job and reweld. Over the years I've had to do it several times for loose baffles--most recently on a stainless kawa super sherpa exhaust where the mild steal inner chamber tuning tube had come loose--it went in the bin! I've also actually ADDED my own dB killers to vastly overpriced straight through aftermarket "silencers" which simply rely on a perforated tube and wadding--which technically is only any good for absorbing higher frequencies--and thats why OE designs also have tuned chambers as well--they DO know what they are doing!-I've found that it also IMPROVES bottom end torque as the whole system design and valve timing relies on a certain amount of back pressure--a straight through may give you a couple of bhp at the top end but you may well suffer from a lack of cylinder filling and consequently torque at the lower end!---why do you think KTM etc put Helmholtz chambers on their downpipes--its to provide a resonance and positive reflective wave at lower rpm to overcome the excessive valve overlap and improve cylinder filling just before the exhaust valve actually closes-it "pushes" fresh charge back in!---the valve overlap is tuned for top end-its a low end torque recovery device.
    --but back to spark arrestors for the US forestry commission--typically these are a fine stainless gauze designed to abstract flame energy and kill any flame without causing ANY ADDITIONAL RESTRICTION--and are usually very visible as the last line of defense.
    mbravo and sKatZ like this.
  5. Noisytim

    Noisytim Adventurer

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    I'm commuting to work every day on the bike about 300km a week. Mostly on freeways at 100kph. I'm very pleased with the ecu swap and the performance improvement. With the ecu loom pin swap making the tacho work perfectly I would never consider swapping back to the stock ecu.
    RiderRider likes this.
  6. Ed@Ford

    Ed@Ford Long timer

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    Chris Barnes: "--but back to spark arrestors for the US forestry commission--typically these are a fine stainless gauze designed to abstract flame energy and kill any flame without causing ANY ADDITIONAL RESTRICTION--and are usually very visible as the last line of defense."

    Your comments on Helmholtz chambers are right on. However, with respect to spark arrestors, actually it's not gauze but screen woven from very fine wire. The "mesh" of the screen is just a tad finer than the "backfire screen" that is on the Rally's air filter. If you read the technical description from USFS (US Forest Service) it is very precise and thorough , AND OLD. The purpose of the screen is to capture glowing carbon particles from the exhaust that could start a forest fire. Well, in our modern age of fuel injection and catalyst, spark ignited engines no longer have sooty exhaust, no less one making glowing hot ones.....but the law is there and it is SEVERELY enforced. Fines start at $500 + vehicle confiscation. So the first way to reduce backpressure is to create (buy or modify) a replacement spark arrestor that has more square inches of screen. The second (in the case of the Rally) is to modify the shape of the spark arrestor in such a way that one helmholtz chamber in the muffler is bypassed. The early CRF-L had a 3 chamber muffler, the 2017 "L" & Rally has 2. The bypassing reduces the twisting and turning the exhaust flow is forced to do. When it comes to "checking" for a spark arrestor, the ranger or officer will probe the exhaust with a rod....it better stop within 6" or 8"...they can also look for "US Forestry Approved" stamped somewhere on the muffler. I have created such a spark arrestor form my CRF-L....it likes the reduced backpressure, sound testing indicates MAYBE 1 or 2 dB louder. I am finishing up a better one for my Rally....because it's spark arrestor is different from the old CRF-L.
  7. Chrisbarnes1

    Chrisbarnes1 Been here awhile

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    ok--understood on the spark arrestors--but coming back to the muffler itself the chambers with protruding pipes in and out of them are there to ensure that there is a rapid expansion and volume increase to kill the low frequency, but the pipes extend into the chamber at "nodes" so as to not transmit any chamber resonance. The Helmholtz in the downpipe is there for a quite different reason -- and is specifically designed to resonate, and is also a specific distance from the exhaust valves to ensure that a positive "reflected" wave pulse arrives at the valve just before valve closure-it travels back up against the exhaust flow--its the same principal as an expansion chamber on a 2 smoke with the first change in section providing a negative pulse for scavenging and the next change in section providing a positive pulse to push fresh charge back into the combustion chamber. Modifying the rear muffler after the gas has cooled down considerably can have very little effect on restriction over a carefully designed OE system---its already had to travel down a relatively long pipe after all--and if you do the calculations the drop in temperature causing an increase in density means that the pipe diameters at the end need to be only about half the header diameter to maintain the same gas velocity-!-Just look at OE exit diameters and you'll see what I mean! An expensive straight through poor "silencer" simply messes up the fuelling and cylinder filling and produces more noise. If you are going down that route then you'll need a bigger bore header pipe to start with and an upfuel---but that probably means a marginal gain in power at the top end coupled with an increase in fuel consumption. Replacing the ECU with one that is designed for the same engine in a different chassis is obviously a sensible start point. Replacing the muffler on its own simply saves weight and provides a placebo effect--at great personal cost!---I'll await comments !!
    jonnylikesvtwins likes this.
  8. Ed@Ford

    Ed@Ford Long timer

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    Chris: Yes, you understand the question(s). The CRF models according to Honda were designed with a longer/smaller ID headpipe to tune the torque peak to a lower RPM than the CB models. Just by looking at dyno data that's floating around out there, it's obvious Honda isn't lying. I've dallied with gadgets to modify the headpipe and it's tuning effects on similar small displacement single cylinder engines. It is possible to get improvements AND problems. The LAST thing I want is noise. I've been successful with improvements on XR200, 250 and 400 models, primarily in getting improved low end torque with spark arrestor revisions. That's why I continuing with my CRF-L & Rally. Having said that, I am excited to see if real dyno data comparing the two different ECU's that are floating around for the Rally is real or "smoke-and-mirrors".
  9. Revelc

    Revelc Adventurer

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    Hey guys.

    After 5 Yamaha’s, I’m considering a Rally for my next bike.

    Have any of you fitted a BBK yet?

    I am a larger rider at 230-240lbs and worry the lower powers CRF might not have enough gusto to get my corn fed arse down the interstate.

    Getting flak for not going with KTM and wanting to mod/uncork a CRF Rally instead.

    Will be used to run 50 miles to the closest OHV park to run their 26 mile enduro loop and back home.

    Most likely will serve for daily driver duty as well.

    Any input is appreciated.




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  10. Mi_ka

    Mi_ka n00b

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    Gentlemen hold your horses! Many detail differences between the models may mean much less hp gains for the CRF-RL (mainly due to the more restrictive headpipe that enhances low rpm output). The most important gain in my eyes is the reported throttle response gains which could be due to possible richer acceleration/open loop maps along more aggressive timing afforded by the steady high quality of the Japanese petrol stations’ gasoline. This way, no need for a half baked piggyback solution that works in contrast to the long term corrections of the ECU that could be affecting open loop maps as well.

    No guy ever popped one open to check for some kind of programming interface like JEDEC etc?


    AFAIK, ECUs usually check the resistance of the heater to verify it is healthy (if not they throw a CEL) along the resistance of the lambda sensing element to verify it is in the proper working temperature range before enabling the closed loop functions based on sensor’s output voltage. The unheated sensor could be different in construction (along different resistance range etc) so have this in mind if any O2 sensor CELs pop along as mileage increases and sensor wear accumulates.


    I agree - I think they went pushing more for the JDM model after they verified the reliability of the imported(8-?) engine. (http://www.honda.co.jp/CBR250R/spec/). They can always count on top quality gasoline for their street bikes. On the other hand, an adv bike may have to deal with rural mexican, greek or peruvian suddenly far from stellar gasoline at the odd remote petrol station (like these F800 guys that blew their piston rings...).It is funny that they have upgraded the obsolete JDM CBR250R single to a twin cylinder CBR250RR over there instead of getting it to the 300cc US version (I guess they must be preparing for a global 300 twin) - anybody remembers the crazy 4inline 250cc RR bikes of the golden age (early ‘90s before their economy crash) that revved to 18K-20Krpm?
    Chrisbarnes1 likes this.
  11. docgonzo

    docgonzo Old Gadfly

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    I tip the scales at 230 as well, and have no problem with my Rally. The rear shock is cranked full on pre-load, but that's the only adjustment I've made. I have 2,300 miles on it, mostly the woods in NJ. No racing, just legal dirt roads and sand in the Pine Barrens. The bike has had no problem keeping up with the BMWs, KTMs, and S10s, but remember, NJ is a sand bar. No hills to worry about, and no rocks.
    [​IMG]
    [​IMG]
    MewZiKat, Mi_ka and Revelc like this.
  12. Mi_ka

    Mi_ka n00b

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    Chrisbarnes1 likes this.
  13. Revelc

    Revelc Adventurer

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    If I choose the Rally, I will definitely giving it the Ohlins treatment front and rear.

    East Texas has some hills and I don’t want someone running me over.

    Did you uncork yours?


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  14. Noisytim

    Noisytim Adventurer

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    1000km with a cbr250r ecu and not one fault code, no smoke, no black exhaust, no stalls, only smooth running and great fuel consumption
    Mi_ka likes this.
  15. docgonzo

    docgonzo Old Gadfly

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    Feel free to "Ohlins" your Rally. While you are spending money, you should "Akrapovic", full titanium it.
    If you think you need to "uncork it", I'd suggest instead just getting a nice street legal 300cc KTM or a Beta.
    The Rally is a fun bike to play in the woods. If you need more, spend a little money and start with a race bike.

    For the record, I had a street-titled KTM 520 EXC for a number of years. It was definitely overkill for the kind of stuff I like to do. I like the Rally better. Worry-free and engineered for kinder and gentler riding.

    p.s., even had motard wheels for the 520, and raced it on the track. Not planning on getting motard wheels for my rally.....
    IMG_0801.jpg
  16. Kevingrahambutler

    Kevingrahambutler Low rider

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    brenhden and Mi_ka like this.
  17. Mi_ka

    Mi_ka n00b

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    completely stock (besides the ECU)?
  18. boboneleg

    boboneleg we can rebuild him.

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  19. brenhden

    brenhden Happy camper

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  20. Noisytim

    Noisytim Adventurer

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    Snorkel pulled and metal screen off air filter, but i had done that prior to the ecu