Chassis Set Up

[busakiller]

Hey guys I was wondering if anyone here knows how to set up a drag bike chassis.

What do I set my sag at?
Ride height? (Swingarm pivot height and rear axle height)


Right now I have my sag set at 9/16 of a inch. The swingarm pivot point is 1 1/4 higher then the rear axle. Without me sitting in it. Bike is sitting 10 inches out and has a revalve stock shock with a gen2 spring. Spring dynod at 754 pounds at one inch preload.

 

[Dennis]

Sounds good for a Busa frame with a DOT tire. I can't say for a drag frame, slick and wheelie bar bike.

 

[busakiller]

It's a non cut rail busa frame with no wheelie bar. Running a shinko hook up. Hope to make it to the track this saturday and get some passes in.

 

[Dennis]

Good starting point.

 

[busakiller]

so made it to the track and no good results. all the changes still didn't help my bike.

 

[AQTCJAK]

hard to tell what is going on with your launch. Provide more details launch rpm are you running launch control, tire pressure what is it doing on launch the more info the easierit is to help

 

[busakiller]

On this pass I launched at 4500 rpms and Tire pressure is at 14 pounds. No launch control or anything. Just right hand control throttle and left handle controls clutch. I have all stiff clutch springs and a ape clutch mod.

 

[AQTCJAK]

here is what I would say I run my tire @15- 15.5# launch at 7-8K depending on track conditions

 

[Dennis]

The leave didn't look smooth. It can be hard with heavy springs. I couldn't hear the pass so I don't know if you spun, but I can tell you there is no way I hook on 15 psi with a Hookup. I run 8 pounds in both my bikes. I could probably get away with more in the stock motor slow bike.

 

[B n s racing]

Well different strokes for different folks but we launch our 6" over gen1 at 6+6500 on 18 psi, if you research that's what a majority of 8 second bikes use picked up that data from a Rickey Gadsen interview.

 

[B n s racing]

That's on a Hookup Pro 190/50

 

[Dennis]

Track prep is a huge factor in what PSI you can get away with. We typically don't have optimal prep due to low car counts so the track doesn't spend the money. Also the 60' you are trying to hit makes a difference. If I'm going 1.26 on my 69" bike it is much more sensitive to pressure than my 67" bike going 1.39. The slower bike is heavier too which helps traction. I run the regular Hookup. The Pro I tired peeled.

 

[busakiller]

They prep really good the days I go. The bike didn't spin on that pass. The bike has been leaving like this every since I got the new motor in the bike. I have 50 some passes on it now and still can't get a 60 foot. Change sprockets, length, heavier rear shock spring, preload, rebound, sag, tire pressure. It just leaves choppy like that everytime.

 

[Dennis]

Without riding it my best guess is something with the clutch.

 

[busakiller]

I will order a new clutch this week then. Lol.

 

[Dennis]

I'm not saying the steels/fibers are the cause. Possibly something isn't square, something is loose, who knows. It won't hurt to change the steels/fibers to see if anything changes but be sure to check out everything else while you are in there.

 

[ColdBusa]

Do you have a clutch mod in it??

 

[busakiller]

Yes bike has clutch mod in it. Just found out I have major engine problems. So going to get that fixed and get back to the track.