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1991 Yamaha fzr400rr

Discussion in 'Other Projects - Other Bikes (non 250's)' started by kiffsta, Feb 10, 2021.

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  1. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    But with big drops in the mid range. Be terrible to ride on the road.
     
    Murdo, Feb 13, 2021
    #21
  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That's why they have an EXUP, not a fan of deleting them, especially on the smaller bikes as you will notice the torque dip in the mid range. On the bigger bikes, less of a problem due to the oodles of torque they have these days.

    Lots of people are stuck in the old ways of thinking - "It's a restriction! Delete it!" - Which isn't always the case.
     
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    Linkin, Feb 13, 2021
    #22
  3. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Yes, I agree that you would never do it on a street bike, but if you're launching at 10,000rpm and over, then surely it's not needed? I guess it might run rough on start up and idle...is that a symptom of malfunctioning EXUP?
     
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    Frankster, Feb 13, 2021
    #23
  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    EXUP on an FZR is supposed to fix a bit of lag around 6000rpm (from memory)

    Its still on the ex road bike/now drag bike FZR of mine but I had planned to delete it on the Flyer

    From what Ive read the exhaust valve on the Daytona is mainly a "noise" thing and every cowboy deletes it totally .... plenty of 'servo buddys' sold to keep the ECU happy I would think on the modern bike

    The Daytona also has an induction flap on the intake which is 100% there for "noise' ... go figure !
    Everyone ditches that also ... or u can just lower the RPM that it opens from 4000rpm to something under idle , so its permanately open, with software
    I like induction howl so eventually I will do that to mine and worry about the 'EXUP" if I ever run a full aftermarket exhaust system

    https://www.motospares.com.au/servo-buddy-exhaust-servo-eliminator/
     
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    GreyImport, Feb 13, 2021
    #24
  5. gregt

    gregt Well-Known Member Premium Member

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    Back in the heyday of F3 here in NZ, i built a few FZR400's. One even with kit cams and ignition. They went well too.
    But the one thing I never did was run an EXUP on a F3 roadrace bike. If you got that low in the revs you were wasting time.
    Thousands on the other hand - and OWo1's - need the EXUP to smooth the power delivery.
    It's been interesting to watch the used/tired FZR1000's come out for our pre89 class here. They've hurt a few people
    They're tyre and pipe sensitive..

    The best FZR400 here came from Wellington. On alky and sponsored by a cam outfit it was very quick indeed.
    Luckily he didn't do the full National series. We did beat him at the WSB round where F3 was a support class.
    But that was with my EX500 kawasaki twin. 72HP at the wheel.
     
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    gregt, Feb 13, 2021
    #25
  6. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Fair enough for race bikes, but on a road bike I would leave it in
     
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    Linkin, Feb 13, 2021
    #26
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