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FCB tech ?'s

This is a discussion on FCB tech ?'s within the Technical forums, part of the Caferacer.net Forums category; Chris could win at Mosport with what he uses at NHIS if his NHIS gearing is 16/33. My bike's redline is 12k. But power seems ...

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Thread: FCB tech ?'s

  1. #11
    Senior Member craig641's Avatar
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    Chris could win at Mosport with what he uses at NHIS if his NHIS gearing is 16/33.

    My bike's redline is 12k. But power seems to flatine at 11. So I shift at 11. I put the close ratio fifth gear in my transmission this year so my gearing may change. We'll find out at the trackday.

    jc, did you end up building a LWSV motor to go with the new body work? If so you'll see that different gearing at different tracks makes a huge difference.

    Craig


  2. #12
    Moderator ROSKO's Avatar
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    Thanks y'all.

    I'm to be in the ballpark w/ gearing. The trapp/ 2-1 combo will just have to be an experiment.




    BORN TO LURK, FORCED TO WORK.
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  3. #13
    Moderator jbranson's Avatar
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    Rosko...I forgot about that.

    For 4" disks I'd start with about 6 or 7 disks.
    For 3" disks around 10-12 disks.

    That should get you close enough that it won't hurt power.


    Craig...let me rephrase that. "You won't win at Mosport with CORRECT NHIS gearing"

    JohnnyB


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  5. #14
    Senior Member ttilghman's Avatar
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    rosko/jb-

    for what it's worth, and i don't know how to start comparing 2-1 with 2-2, but i'm running 12 on each side of 4"ers on a 2-2. i started with 10 disks, stock jetting, and stacks, and was OK in the early morning practices, but boggy-wet rich in the afternoon at frontierland last fall. recently, i ran 12 each and rattled them a little loose at 50-70deg VIR and seemed pretty good....so i may add more as the temps increase? steven baker was at 12 too i think...but he may be running 3"ers?

    and rosko, i've been running 16/34 and seem to be touching the top everywhere jb suggests, but i'm thinking i'll try 16/36 next time at NHIS to see what it does....damn i wish we had transponders.

    and valve clearance on the followers? .002" intake and .004" exhaust.

    -tt


  6. #15
    Administrator texmawby's Avatar
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    i run the stock setup everywhere and at nhis i hit 5th just past the stripe (i go thru t10 in 2nd gear usually).....

    texy


  7. #16
    Moderator jbranson's Avatar
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    There is a ton of mis-information about trap disks and 2-1 systems. If you are running rich with 10 four inch disks then the problem lies elsewhere...that's enough for a V8 to breath out of.
    For instance...I run 6-7 3" disks on a 2-1 209cc bike that I turn 12,000 rpm..and it makes about 25hp.

    Secondly...you don't need more disks on a 2-1 system than you do on a 2-2 system. I've almost given up trying to explain this. Both cylinders DO NOT breath through the exhaust at the same time...so you do NOT need twice the disks. Unless two exhaust pulse enter the collector at the same time...you effectively have only once cylinder exhausting through the megaphone at one time.

    There is no convincing people that big loud exhaust doesn't mean more power.

    TT, you JET for weather changes, you don't change the exhaust (yes I know you know that). Change two disks out of 12 will make absolutely no difference in rich/lean except in your mind ( Don't take that in a mean way). Sounds like your bike is altogether too rich...just like most 350's I see on the track. You have to get jetting close before you can begin to do the very subtle tuning of the exhaust.
    If your exhaust is ever wet sooty in ANY conditions then it's too rich by quite a bit. Trapps will make them look richer just because most of the soot hangs around rather than disappearing out an open meg.
    If you dropped a couple of jet sizes you'd probably see more of a power increase than anything you can do with the exhaust. On race fuel the tailpipe should be a medium gray...might be light gray on a cold day....darker on a hot day.
    You dyno tuned it to get the jets dailed in right?
    JohnnyB

    PS. I started my exhaust system at 1.250" OD...now I'm going to 1.125 OD...yes smaller..the same system used on Mary's 175...you know..the one Zack rode and did times that would pretty much trash the whole FCB field. And I'm even going to build and try a 1" OD system...which by the way is what Mike Rich recommended....and I don't know what to tell anyone that doesn't know what a tremendous tuner he is.
    Last big bore 175 I had in the shop (240cc)...built by Craig Hanson out west...guess what...had 1" OD head pipes.

    It's about hp, not size, not noise.

    This is a biggie folks...a bunch of you could be going faster. Get to a dyno. I trust nothing but a lap timer and a dyno.

    PSS. I'll edit yet again...don't want you guys to think I'm being nasty here. I just feel for you guys...a lot of you giving up performance. A lot of you guys are getting fast enough that it's time to give up the wive's tales and guesses and do some research and development. Think about it...what do all the fast guys have in common...they know their bikes extremely well, or have them tuned by experts. Seek out the advice of the guys that are going fast, or the guys that build their bikes. Attention to detail is everything.



    Edited by - jbranson on Apr 04 2007 02:26:55 AM

    Edited by - jbranson on Apr 04 2007 02:38:59 AM

  8. #17
    Moderator joe c's Avatar
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    i lost my free dyno connection. damned ross! my bikes a stocker but i built the frame with the intention of doing a lw/v1 motor one day. chris ran daytona gearing at nhis and still managed a uscra championship. and that was when it was hard to win at louden! and that was with a "4 speed". itd be alot like zach winning fcb on that pos he was riding though. i think put him on just about anyhting half way decent and hes the kind of guy who can do well. im sure weight makes a huge difference. think pedrosa is running the same gearing as hayden? anyway, late for work....ill count teeth this week. i have chris' bike at my shop. i agree with everyone.


    jc


    aaron, send my wheel.

    Edited by - joe c on Apr 04 2007 08:38:12 AM




  9. #18
    Senior Member ttilghman's Avatar
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    jb-

    no, all's good. i appreciate the help. i wasn't suggesting anything for disks, just relating my numbers for discussion. i've never run a 2-1 so haven't even thought that through.

    and yeah, i'd love some dyno time and would kill for a lap timer (one of the great things with WERA is the transponders). i'm not looking for loud or chasing wives tales really, but just experimenting and stopping once the thing is running well. my only testing is seat of the pants and plug chops. the plug chops are where i've seen evidence of richness paired with the WOT bogging...and adding two disks did something? the bike was good before baker ran over the old megaphones and when i switched to the marshall/branson exhaust w/10 disks, it got rich? i've already got the smallest mains i can find for the OEM carbs, i'm running cheap v-stacks and am looking to cut the screens out, if for no other reason than to keep H2O from hanging there in the rain(thanks tanner) but maybe i'll get more air? i've been running race gas for the lead, obviouisly not the compression, but MikeO and Tanner have convinced me to run pump gas with marvel if anything at all.

    no doubt you're right about proper testing....i'll get there. and just to put things back in perspective from my POV, i'm just pulling my alternator this weekend and trying to get the rear brake involved enough to do a little trailing. no doubt i'm chasing my tail on some issues, and once my bike is really race prepped i'll be stoked, which will include a fresh top end, i mean i've got decent compression, but have no idea what else is going on in there. but it's still a real hoot working in that direction, a process after all, and i don't mind riding around some issues as long as i have a chance to work on my riding each time out.

    wankin'along-
    tt


  10. #19
    Moderator joe c's Avatar
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    dude, that sounds perfect to me! youll probably chase your tail until you get everything freshened. its tough to diagnose shit when there are things in question. especially if you havent seen it for 40 years in a row like other guys here. (frank) i dont think you really need to be worried about being fast enough. ya seem to have that covered!



    jc


    aaron, send my wheel.




  11. #20
    Senior Member lonewolf's Avatar
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    I run 16-36 and hit 5th at the start finish every time Right now I have 7disks on my 2 into 2 exhaust. I plan on taking one off.I still run very sooty exhaust with my 110 jet.I'm still looking for something smaller.


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