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FZR 2kr main jets

Discussion in 'Yamaha 250cc In-Line 4's' started by robm569, Apr 8, 2012.

  1. robm569

    robm569 New Member

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    Hi, Have just rebuilt 89 FZR 250 2KR. It has Carbon fibre slip on and pod filters. The jets are maked to 75, a .75mm drill bits fits the hole. I've had to set the needle to the leanest position (clip at top) otherwise it fouls plugs. The performance is ok under 12k but doesn't like to rev much unless it a cold night.
    Has anyone here worked the best main jet to use for a 2kr with these mods? If I had the original exhaust and air box I would try it but didn't come with the bike. Cheers Rob <!-- s:cheers: --><img src="{SMILIES_PATH}/th_Cheers.gif" alt=":cheers:" title="cheers" /><!-- s:cheers: -->
     
    robm569, Apr 8, 2012
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  2. dontz125

    dontz125 Active Member

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    The jet sizes have nothing to do with the bore, but are rather an indication of fuel flow rate for a given time at a given dP. The jet number should be stamped on the face of the jet - look at the end of the jet while it's in the carb and you should be looking at the number. Stock mains were #72.5.

    Check your fuel height; you may be way too high resulting in excessive flow through the jets.

    Make sure your pods are clean and LIGHTLY oiled; a common mistake with pods is to oil the crap out them. This results in LESS airflow than the stock setup!
     
    dontz125, Apr 10, 2012
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  3. dave

    dave Well-Known Member

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    Sound way too rich.
    Pod filters do not seem to work real good on the FZR... The carbs are setup to work properly with the standard air box.
     
    dave, Apr 12, 2012
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  4. Jay1

    Jay1 New Member

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    I have tried this mod and it could never get it to run properly with my 3LN3. Replaced all the seals on the airbox and blew out the filter and she runs heaps harder, throttle response is amazing but the nights are getting colder here and these bikes mave a much nicer throttle response when the engine is hot and the air is cold.

    I found something that others might find useful though. Found this on the Kiwibiker forums...

    Maybe that could give you abit of guidance. I know that this mod is possible I just didn't want to waste a thousand hours of my life getting it to run. Factorypro don't do kits for 250 carbs either, which sucks.

    Find yourself a second hand airbox with an airfilter, will probably get your bike running alot faster than trying to tune pods
     
    Jay1, May 4, 2012
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