Home Forums Road Racing B stock class with Yamaha engines?

This topic contains 7 replies, has 4 voices, and was last updated by  Ian Krueger 1 month ago.

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  • #73552

    Ian Krueger
    Participant

    So I’ve contemplated building a B stock someday maybe next year or so depending on my living situation. My issue is I’m 5’7″ 125lb fully grown adult (lol) and making 465lb with the IAME motors is going to be pretty much impossible for me or unsafe amount of ballast.

    My question is, if I run the class but with Yamaha engines instead, weighing I think 390, would that be sort of competitive still? do anyone run Yamahas in b stock?

    I struggle to make weight in sprint class, carrying 80lbs of ballast lol.

     

    And input greatly appreciated ūüôā

    -ian

     

    NHKA member, yamaha pipe sr

    #73562

    Mark J Schoonover
    Participant

    Yamaha & Piston Port engines: 395 lbs., 100cc Controlled: 465lbs.

    #73579

    Mike Peters
    Participant

    2 Yamaha’s make¬†only a¬†little more HP¬†than 1 Reedjet.¬† Might work with a pair of Comer P51’s but kind of iffy. The new X30 laydown class might be a better choice. Almost as fast as a B-Stock. Weight is 410#. The CKI that Lindsey Read drove at Daytona last year weighs about 230#. Add your 125# plus gear & your getting close. Alum fuel tanks will add some. Pretty easy to get to 410#. BTW Lindsey weighs about the same as you & ran with 5# of lead to make 385# to run F125

     

    #73615

    Ian Krueger
    Participant

    okay thanks, yeah i knew the controlled engines were a lot more powerful, but i didnt realise it was that much! yeah and thanks for the suggestion. I’m born naturally as a yamaha guy, grew up with them for 10 years, so the rotax laydown doesnt appeal to me as much, but still a nice comment. yeah i don’t have nearly the budget for f125 , or any knowledge on how they work, performance tuning wise. If that’s where the top laydown classes steer towards within the next decade, i might jump in later on. but the oldschool aircooled was always the appeal to me :). yeah i guess i will spend the next couple years scrounging for a pair of Pirellas or soemthing, thanks again for the advice Mike

    NHKA member, yamaha pipe sr

    #73621

    Mike Peters
    Participant

    It’s not a Rotax, but it is water cooled. The X30 is an IAME/Parilla. Initial cost is a bit¬†more but maint is less. I agree air cooled is a lot less hassle. Ran a pair of Atlas reed valves on my GPX200 back 30 years ago.

    #73701

    Ian Krueger
    Participant

    Oh okay. Yes I remember now, reading about it awhile back. yeah it comes down to having (one) axle clutch already, quite a few kt100s, all the belt drivers and stuff so i think i’ll just stick with the 2-cycle stuff for now. it’s all still just planning 2-3 years down the line. yeah it really comes down to what i have for spares, if i switched to the watercooled stuff, it would be quite the investment just getting spares of everything.

     

    thank you for the advice in any case.

    NHKA member, yamaha pipe sr

    #73814

    John Mulvihill
    Participant

    If you really want to go the Piston Port route under the current rules, I’d look at a pair of K71’s (AKA KPV, HPV).

    Better quality than a Yamaha KT100.  Not much more expensive to rebuild.  Still uses a Walbro WB3a so tuning is similar.  Each motor is about 5 pounds heavier than a Yamaha. And 3-5 more HP each.

    Under current engine rules the K71 is very close to a Comer P51.

    Since the TaG 125’s came in, there are a lot of K71’s available used.¬† I bought 4 for under a grand.

    John

     

     

     

    #73832

    Ian Krueger
    Participant

    oh wow, thanks john. Yeah i’ve never run a reedjet before so I’d imagine they are a bit more expensive to rebuild.

    Yeah i have seen the Komet’s around and yes we use the WB3a carbs as well so that will be nice.

    The main problem I’d face is the fact that I’d need about 150lbs of ballast to make weight with a reed pair, which would be very terrible to balance, and wouldbe even worse news if i got in a crash.¬†I’m not going for competitiveness, but I think with the lower weight and the Komet set up that might work. Like I said it’s kind of a crappy excuse but since i’m so short yeah it’s very challenging to make 360 for my sprint class, let alone 465 for the reedjet B stock lol.

     

    Thanks for the suggestions John!

    NHKA member, yamaha pipe sr

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