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  1. #1
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    Jun 2002
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    Dyno Comparison: Stock vs. Mo Betta?

    It's about time for another top end on my '99 YZ250. This time, I was
    thinking about sending it off to Eric for some porting. I've looked at his
    web site and read about "power bands", but I still have some questions.

    1) Does Mo Betta porting mean racing gas? (I use Chevron premium,
    and I'd like to stay with that)

    2) Anyone (Eric?) done a dyno tace of a stock engine versus one that
    has had the Mo Betta port job?

    3) I'm really not looking for peak HP (got penty now), rather a nice
    broad pull from the engine. Don't really like the bikes that "hit"
    really hard either.





    4) I'd like an engine that "carburettes" really nicely everywhere.




  2. #2
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    Eric will give you the best of both worlds, the Mo Betta porting and the ability to run pump gas, unless you specify that you'd like it tuned to run race gas.




  3. #3
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    Nov 2002
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    As far as dynos go I'm sure EG porting will produce much more power...Back in 93' eric did my cr250r (which was fast in stock trim) and it just made even more power...The bike was strong everywhere...Bottom...Mid....Top..Not only that but the bike felt like it ran through the rpm range much quicker....I mean, you turn the throttle at almost any rpm setting and BRRRRAAAAAPP!!!
    Slow 180 degree corners in second gear....Roll on the throttle and..BRRRAAAP!! and you had better be as far forward as possible because the front end was coming up so it was actually more controllable by going up a gear higher in the corners and using a little clutch....one word...WOW!!!

    I took a look at the latest Motocross Action and the pro circuit modded kx250 yielded 51hp where the stock 03' kx made 42.9 which is a substantial difference...

    The only thing is I think pro circuit is kind of generic...I don't think they would treat a regular customer with the quality work as they would when they know it's a magazine test bike or one of their sponsored racers..Maybe I'm wrong but I think Eric Gorr would do Higher quality work...
    Anyway, I'm sure that your YZ250 would put out 50 + hp at least properly modded with race gas...




  4. #4
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    I had Eric give my 94 YZ250 the Mo-Better porting and had him set the head up for pump gas. Let me tell you this when using a lower gear=rocket using a higher gear=tractor. The power comes on early and signs off when the pipe does and it does it very smoothly. I like it better than the stock porting which had a violent hit in the mid range I also did the powervalve governor mod Eric describes in his book for this year which also helped.

     

    Steve



    m y   s i g n a t u r e:


    You say Redneck like it's a bad thing.

    "If my calculations are correct when this baby hits 88 MPH you're gonna see some serious $#!+."

    Doc Emmit Brown, Back To the Future

  5. #5
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    I was a beginner on a 2000 KX250 and I didn't feel comfortable with the way the front tire would sometimes come up as I left the face of a jump - but I didn't want to give up any power.

    I had Eric convert the engine to a 310 with mo' better porting. I couldn't be happier! The bike pulls like a tractor and is always predictable now.




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