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Help Race Gearing Help

Discussion in 'Honda 250cc In-line 4's' started by rustys, Jul 13, 2017.

  1. rustys

    rustys Active Member

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    At the moment I am Running a stock 17/52 gearing with a 420 chain, but need to taller gear the bike a bit more, I would like to go to 17/55, JT rear sprockets only go to 52, so I may have to cut a blank. I am also going to replace the chain with a new 428 MX. Anyone with any other suggestions or ideas..
     
  2. kiffsta

    kiffsta Senior Member

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    MC19 CBR250R run a 54T as standard so that will work, from what I have seen, a lot of the guys who race MC22's run a 15t front, they are not available standard so I hear the guys buy a 17t , cut the centre out and weld it onto a 15t sprocket. As for chains, most run a 428 non O ring chain

    Check out this site, @simidau is a bloody quick on an MC22 and posts what sprockets they run at different tracks.

    http://teamtiger.com.au/bike-preperation/
     
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  3. rustys

    rustys Active Member

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    Thanks for the Info Kiffsta. They have some great info on that site (so I have saved it) just what I need to know to get some base set up. Need to know whether they remove the Air box restrictor as they don't mention that at all.
    I would also look at a Quick Throttle set up from Simon as well if I could get a costing on one.
     
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  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    To give it taller gear's, eg higher ratio for more top speed you want to fit a smaller rear sprocket, or larger front if they make them and if it'll fit.
    Bigger rear sprocket will give it a little more torque but lose some top speed

    Use this to calculate what gear's you need, it show's the speed gain and torque loss or visa versa
    http://www.sprocketcalculator.com/
     
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  5. rustys

    rustys Active Member

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    Thanks "my67xr" thats what i have been looking for. Cheers.
     
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  6. rustys

    rustys Active Member

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    Thanks guys for your help.
    Found a 57T Blank on E-Bay that suits the 428 chain which I had to lengthen, we machined it out to fit, so still running the 17T front gaining 5% more torque which chart shows and what I wanted, we did not loose to much top end and have gained another 3 seconds a lap easily. With the recent engine tune up of bigger mains lifting the needles 1ml and derestricting the airbox I have made a total gain now of 6 seconds a lap and bike running sweet. So last race meeting the MC22 was right in the leading group of about 10 bikes a mix of KTM390 Yamaha R3 and Kawasaki 250's and boy were we having fun. Now just fitting a quick turn throttle I have just purchased from Simon from Tiger Racing so all looking good for the next battle.
     
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  7. gregt

    gregt Well-Known Member Premium Member

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    What track/club in NZ are you running with ? Around ChCh I'm pretty sure you wouldn't be allowed to run with that crowd.
     
  8. rustys

    rustys Active Member

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    Hi gregt.....Victoria Motorcycle Club / Track Manfield. It used to be called "Street Stock" class, now called "Development Class" where they run combined Streetstock 150 2 strokes and Paralle Twin 250s as one class, and KTM 390's against the inline 4's 250's as another. Three years ago they changed there Racing format in Classes no Post Classic Racing at all, F1 and F2 is run as two events "Senior Sprint" and "Senior Trophy" Class with (600cc and 1000cc) bikes combined, and all the rest is "Junior Sprint" and "Junior Trophy", not many people like it, but because of the reduced number of classes, and you want lots of racing and track time you certainly get plenty of it. They also run a Motard Class as well, Hamilton Motorcycle Club run there racing similar. As my main race bikes are Post Classic i have never bothered entering them up against modern day race bikes, so thats why i'am racing the CBR250R in their events at the moment, and the bike seems competitive enough and loads of fun, also its a bit cheaper to enter.
     
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  9. gregt

    gregt Well-Known Member Premium Member

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    Pretty sure MCI wouldn't let you in the development class. They get large entries of the "correct" bikes... Down here, you'd be running at CAMS meetings where you'd find a 1502T/2504T class plus you'd get into pre 89/pre 94. CAMS run at both Ruapuna and Levels so you'd get plenty of racing. There's a lot of dedicated classic/post classic meetings down here - unlike the NI...
    What times are you doing on Minefield ?
    If most of your bikes are posties, look at coming down for the Southern Classic in December at Levels.
     
  10. rustys

    rustys Active Member

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    Every Clubs different these days the way they run there meetings, as i say this Format is not in the best interests of a lot of Racers, but you have to go with the flo, Vic Club does not run a Pre 94 class either. Doing low 1.26 at Manfield on the 250, only had two meetings on it so far, used to be the wifes ex Race bike but to good to part with it.
    Yes we have already booked the ferry for the Southern Classic in December, we are racing Pre 89 Yamaha FZR 40/60 3TJ1 Bike number 199, come and say hi.
     
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  11. gregt

    gregt Well-Known Member Premium Member

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    I will. Were you the 600 builder I answered some questions for via Drew ?
     
  12. rustys

    rustys Active Member

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    I have two of them the same one set up for dry the other wet it could have been Ernie Cudby, but i also know Drew as well. I am also on Kiwi Biker Forums under Rustys.
     
  13. gregt

    gregt Well-Known Member Premium Member

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    Must have been another mate of Drews. Haven't seen Ernie for donkeys years. He may remember me - I built Tony McMurdo's Kawa 500 engine and Mark Taylor rode my 500 too. Just bring the F3 support race for the WSB back to his memory....Mark on my bike won it. Ernie wasn't happy....
     

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