Question for 'U' who like to race?

[Smoke_Dog]

O.K. got a buddie who has a problem of the front end coming up off the line in second.

1. Has stretched the bike out 6 inches

2. Lowered it, but raised the rear back to stock, due to it rubbing the undertail

3. Still doesn't have the aftermarket triple clamp/tree

4. Bike has more than stock power, just can't keep the front from coming up, and of course when this happens the individual his racing goes by and his then trying to run him down at this point!

Please pass on some of that good wise knowledge that I know you Busa-ologist have.
Thanks!
SMOKEDOG

 

[Projekt]

Is he using a strap on the front during runs?

 

[Professor]

Should have a strap on the front. If you haven’t played with the settings, put more preload on the spring and tighten the compression and rebound to “0â€￾ clicks.
You have to get that back lowered but you are having problems with the undertail rubbing. 6 over is going to make it closer to the undertail. Some undertails have more clearance than others, but you are likely seeing too much travel due to the spring and valving.

The stock shock/spring will not work correctly with a longer swing arm. Heck if you weigh over 160 lbs, it really is not correct at stock wheel base. More than stock power is going to make things worse.

Find an aftermarket shock or buy a used stocker, add a spring and have it revalved.

You might even consider changing the tail and undertail to a 4â€￾ over unit.


How have you lowered the front without modding the triple tree cover/clamp?

 

[BigDiesel]

+1000 on the rear spring setup- I just got a new rear suspension from GPW @ Hyperbike and its a thousand times better than stock spring/shock combo.

I cant say what exactly the setting your boy shud have, but I went to a 1000lb. spring out back witha revalved stock shock and although I have yet to run at the track, I have troulbe gettin the front up even when tryin on purpose (i am running a Vortex triple tho, 3/4" lower up front). My stretch is also a lil longer at 9" out but mine's just for looks anyway, didnt plan on hitting the strip til next year...til my buddy GPW sent me a killer one-piece suit for racing!

did I mention GPW is da shiz-nit? no? well, GPW happens to be da shiz-nit, just so ya know

ps:a two-step rev limiter might help your guy come out of the hole easier too-alot smoother goin into 2nd anyway. just my .02c

 

[Southside Playa]

I am big dude. I actually went with a strut on the rear to prevent rubbing, which is good, but also bad. If you don't get the tire just right it is subject to spinning of the line, especially on the street at 9 inches over, where there is no assistance from VHT. Eventually I will go with the 1000lbs spring.

GPW sent me my pipe and power commander. He is a good dude. I may just take him the whole dayum bike one day and tell him to make her the beast she is capable of being.

Good luck to your buddy.

 

[WWJD]

I'm not really a racer, but isn't keeping the front down MOSTLY about rider skill? I mean, you can't just twist the throttle full open and expect it to stay down, lock in and go.... you gotta control your roll based on power VS surface, weigt, and tire and stuff, right? Skillz? just a thought. Like I said, I'm not a racer other than road course

 

[Professor]

(WWJD @ Sep. 25 2007,10:32) I'm not really a racer, but isn't keeping the front down MOSTLY about rider skill?  I mean, you can't just twist the throttle full open and expect it to stay down, lock in and go.... you gotta control your roll based on power VS surface, weigt, and tire and stuff, right?  Skillz?  just a thought.  Like I said, I'm not a racer other than road course

Yes, rider skill comes into play but you having the correct tool helps execute the maneuver.

Put a set of Pilot Road tires on your bike at the next track day and see how much more skill is needed to keep upright and on the track. Sometimes you have to tune the bike to the task but as you said you still have to have the skills to perform it correctly.

 

[JuiceSC]

Wheeliebar.....

 

[Smoke_Dog]

(Projekt @ Sep. 26 2007,05:07) Is he using a strap on the front during runs?

No strap! Do you need this if you upgrade to the after market triple clamp, which allows you to go up or down on the front end as needed?

 

[Smoke_Dog]

(Professor @ Sep. 26 2007,05:28) Should have a strap on the front. If you haven’t played with the settings, put more preload on the spring and tighten the compression and rebound to “0â€￾ clicks.
You have to get that back lowered but you are having problems with the undertail rubbing. 6 over is going to make it closer to the undertail. Some undertails have more clearance than others, but you are likely seeing too much travel due to the spring and valving.

The stock shock/spring will not work correctly with a longer swing arm. Heck if you weigh over 160 lbs, it really is not correct at stock wheel base. More than stock power is going to make things worse.

Find an aftermarket shock or buy a used stocker, add a spring and have it revalved.

You might even consider changing the tail and undertail to a 4â€￾ over unit.


How have you lowered the front without modding the triple tree cover/clamp?

haven't lowered the front as of yet!

 

[Professor]

I would think you still do. (unless you are running cut forks built to have a limited up travel) What it will help is limiting the amount of rise of the front before it is lifting the wheel. When you launch without one, the front comes up about 1-1.5 inches and before the weight of the front wheel, axle, brakes start having effect on holding down the front.  It also acts like a slide hammer when the forks hit the stop providing even more inertia to pulling the front wheel. Then there is the angle, the higher up the less power it takes to move it further (although a very slight amount)

But with a long arm you still are going to have to have weight transfer. So you may need to play with the adjustment so that it lifts a bit to help plant the rear tire.


Disclaimer,  I don’t run your combination and I’m looking at it from a theory standpoint and basing it on a couple years of watching others at the track and on-line revealing their experience. (and throwing in a bit of drag car, motorcross, and sprint car chassis set up experience)

 

[Smoke_Dog]

Thanks Professor! I'm trying to find the link to GPW @ Hyperbike at the moment to check out this spring/shock combo he provides! I'm wonderin if it's the Ohlins shock he provides?

 

[Smoke_Dog]

Is this the link I'm looking for?

 

[Mr Bogus]

Why don't more bikes run wheelie bars? weight? handling?

 

[Professor]

Motocross guys have been using a front end travel limiter for some time. It latches into place and holds during the launch. Once they brake and the front comes down to load for the turn it releases by a spring and then allows the full amount of “upâ€￾ travel

 

[Professor]

(Smoke_Dog @ Sep. 25 2007,12:46) Thanks Professor!  I'm trying to find the link to GPW @ Hyperbike at the moment to check out this spring/shock combo he provides!  I'm wonderin if it's the Ohlins shock he provides?

Do a search here. BigDiesel has some pictures of the one Greg had built. It is a stock unit that has been revalved and sprung. Ohlins and Penske and a few other make some better units but at a much higher price.


I just noticed your post that he is not lowered in the front yet. I'd get that taken care of before spending the big coin on an Ohlins or Penske unit.

 

[Professor]

(bogusLogon @ Sep. 25 2007,12:54) Why don't more bikes run wheelie bars? weight? handling?

Several reasons

Class rules in some cases.

Fear of ridicule for running “training wheelsâ€￾ or “sissy sticksâ€￾

Wanting to drag race in a “street legalâ€￾ form.