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hey zach - edit: some good racing info at the end

This is a discussion on hey zach - edit: some good racing info at the end within the Vintage Motorcycle Racing forums, part of the Caferacer.net Forums category; quote: That sounds like Gary Jedniak (sp). Super nice guy...but not very fast. JohnnyB i second that, super nice guy. sounds like him too, 350 ...

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  1. #21
    paced_haste's Avatar
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    quote:
    That sounds like Gary Jedniak (sp). Super nice guy...but not very fast.
    JohnnyB

    i second that, super nice guy. sounds like him too, 350 harley. my dad rode that bike, says it's kind of a handful. it looked like it had kind of a long wheelbase, is that an aermacchi thing?

    Z


  2. #22
    Moderator joe c's Avatar
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    ok, next question. if the harley seems to have a long wheel base, and it not be good, why would you want to put an extended swing arm on things?? for example, people say to use an sl swingarm on the cb becasue its an inch longer. jb m,ade a longer swingarm for his 175, right?? or is that to adjust for the front end geometry?? seems to me, if the front is undesirable, a longer swing arm wont help it. also seems like you want the most compact package you can get without letting it get handling poorly. anyone?? bueller?

    jc






  3. #23
    Administrator texmawby's Avatar
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    zach,

    it wasn't a track day. it was a racing school that they held on a uscra race day at loudon. we were done after lunch.

    i think you would really enjoy riding/racing a properly prepared 350 aermacchi. frank giannini has two of them, both 350 cc, but i don't know if he has them back together. lots of midrange, and some say it handles much better than a ducati. maybe if you see him you could get a ride.

    o.k., back to my spanish lessons.

    caio,

    tex


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  5. #24
    paced_haste's Avatar
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    i like joe's question. most of these bikes that we race were street bikes at one point (or still are). and street bikes tend to be heavy in the rear, so doesn't a longer swingarm put more weight on the front end? lord knows it's not to prevent wheelies under acceleration. but you probably sacrifice a little bit of agility doing that. i don't know the answers to any of these questions but i like my guesses.
    and tex - i've got a ride on a nice 350 that handles just fine. but tell giannini to get his bikes together and we'll race. y'know, just for a laugh.

    Z


  6. #25
    Moderator jbranson's Avatar
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    Longer swingarms are done for various reasons...on a superbike it makes the rear suspension behave much better on hard accleration out of corners. On bikes that are light in the front it transfers more weight to the front. On bikes that are short wheel base and squirrely it makes them more stable in the sweepers.

    I want a longer swingarm on my 175 to get more weight in the front...cause of my size and because they are ass heavy to begin with. It won't hurt to increase the wheelbase a tad to make it behave a little better under power out of corners either.

    JohnnyB


  7. #26
    Administrator texmawby's Avatar
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    tell em yourself, turkeytits!

    tex


  8. #27
    paced_haste's Avatar
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    think it would work to pitch the bike forward too johnnyB? raise rear ride height and slide the forks up in the triple clamps a little? i'm not even sure if you can do that on vintage bike, but that might help too.
    the swingarm thing - the superbike effect of instablity under acceleration is probably present for us too, we just don't notice it because it's so mild. so lengthening the swingarm will probably help with that too, though it might not be noticable.

    Z


  9. #28
    Moderator jbranson's Avatar
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    Raising rear ride height/dropping the forks is common on late model bikes to quicken the steering. On vintage bikes it's typically just dropping the forks (cause rear shocks are a fixed length)...problem is if you just drop the forks you can start to have ground clearance problems. I had to fabricate some taller rear shock mounts on Mary's bike to get the back up some....would have been better to just get shocks the right length I guess.

    I'm hoping a longer swingarm calms my bike down out of the corners...like you say, not very noticable on vintage bikes...but combine steep lean angles with skinny tires and a short wheel base and even vintage bikes can dance around a bit under power out of corners...I know mine does. Probably an issue of excessive weight on the rear than actual hp. I guess pretty much regardless of bike and hp, if you are pushing your traction limit and then add the component of hp to the mix you can make anything break loose.

    Last year coming out of the hair pin at the bottom of the hill at Frontier Land, every single lap the back end of the bike would slip a couple inches, grab, slip a couple inches, grab..about four times in about a second and a half, then it would settle down. It wasn't scary just because of the way the track is there I didn't have any worries about losing it...but it was unnerving and made me think about backing it off a hair there. Which is not something you want your bike telling you if you can do something to fix it.
    JohnnyB



    Edited by - jbranson on Feb 04 2005 12:21:44 PM

  10. #29
    paced_haste's Avatar
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    yea i found the place with the least traction at frontierland was the dirt on the outside of the corner. doesn't take much HP to spool it up out there...it's weird.
    i agree with your ideas about rear traction too. i definitely think that most of the rear traction issues come from too much weight back there. we get rear chatter every now and then with pete's bike. that's what he shoots for, if both ends of the bike break loose, then he figures it's pretty much at the end of potential traction. it sucks though, because it so depends on how the corner is built. downhill always equals front chatter, uphill equals rear chatter. the flat ones are the only times that i can feel like i'm getting the most out of the bike. ever get loss of rear traction out of the last turn at NHIS?

    Z


  11. #30
    Moderator jbranson's Avatar
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    I think the pavement at Frontier has a lot to do with that. Check the difference between there and the main track. Frontier has much larger agregate (rocks)...the rocks polish up nice with use. Get a little sand on them and it's like sand on a concrete floor, pretty slippery. The main track has very small rocks and lots of rubber....course to you the "outside of the corner" sometimes means off the track so yeah...traction would be limited out there.

    I don't think our little bikes get much chatter because A: the wheels and tires are quite light..B: they don't go that fast. From what I understand chatter is the inability of the suspension to react fast enough to the surface of the track. Less unsprung weight helps...but a faster bike is hitting all the little bumps faster...which raises the frequency that the suspension must be able to respond to. So coming down the hill in the back of the main track, if you are carrying an additional 5-10mph of speed, plus have more unsprung weight I can see it causing chatter that I'd never see on my bike.

    I've broken the back loose out of 12 once on my bike going inside someone on a larger bike and getting on the gas real hard in a lower gear to try to get the jump on them down the straight. I also had it happen a couple of times on Marhan's RD350 during an edurance race in the wet. It usually doesn't bother me much in small doses. Even on small bikes throttle control is really important. Riding a high hp, late model sport bike even on the street helps....you just don't go whooping the throttle wide open if you want to stay upright.

    It's amazing watching a race how many people come out of a corner and snap the throttle open like they are going to tear it off the bars, it looks almost comical, like they are trying to kill something. You can get away with it on vintage bikes most of the time. But when you get close to limit of traction it sure doesn't help things. Also most of these little engines don't respond well to that kind of throttle hand...they don't have acclerator pumps, and have narrow powerbands..a person would probably actually go a bit faster rolling the throttle on smoothly. It's all relative I guess...by rolling on smoothly I mean taking one second to roll it on rather than snaping it open as fast as you can. Probably the more hp the longer the "roll" would be.

    Braking is what bothers me the most, and where I could use some pointers....I'm just not sure how hard to pull that lever. I'm used to bikes with giant twin disks up front where it's pretty obvious when you are reaching the limit of the brakes. With drums I always wonder if I should just pull that lever as hard as I can to see what happens. And over bumps if you get a drum air borne for a fraction of a second it can lock up and stay that way when it touches back down, disks seem much more forgiving in that respect. Disks feel very linear to me, drums have that initial grab...then an exponential increase in power...then....nothing more it seems no matter how hard you pull the lever. But I guess different compounds work different ways.
    JohnnyB


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