How far can forks be slid up ?

[Fury1]

Hi all.

I owned and raced a GSXR 1100 some years ago. To lower the bike for dragracing I bought an ohlins rear shock and wound the preload as much as possible - got 4 inches lower in the rear.

In front I cut the internal spacers down to use with aftermarket springs that were longer than stock for street riding. This same spacer worked well with the stock springs to lower the forks internally 2 inches. I then slid the tubes 3 inches in the triple clamps for a total of 5 inches lower in the front. I did have to pull the front fender and side plastic panels for tire clearance issues. This setup had my open header 1 3/4 inches off the ground but I made tech at 3 different tracks (2 inch min.). Slamming this much (as well as weight losses and some other minor engine things got me from 11.3 down to 10.6 on a stock engine.

Any way I'm making a complete list of the mods I would do and in what order I would do them to take a new busa to pro street. I see aftermarket spacers are available to do the internal fork lowering or I could just cut the stock ones if possible - I haven't been inside the busa forks nor do I have access to any to look at right now.

My main question to anyone in the know is can the tubes be slid up the triples (with an aftermarket top that has open holes for the forks) as much as I want ? I have read there is a taper to the external tube that only allows an inch or so before the bottom clamp won't pinch properly. Is this the case ? If so do all the pro sreet guys have their fork tubes cut down ? or rake the head ? to get real low ?

Thanks guys.

 

[Busa1166]

Mine is lowered 1 inch for comfort with an after market triple. Wouldn't the racing straps be enough for ya for the drag strip ???

 

[djsin]

mine is lowered only 1 inch and it will bottom out on the fender and horn...if you land hard enough from accidental wheelie..also i see alot of oil pans getting cracked and broke from busa's being to low...use descretion

 

[Fury1]

Hi Guys.
Thanks for the replies.

I understand the issues. I would remove the front fender and horn for racing. Also the oil cooler if nec. Needless to say on my gixxer I would bounce and compress the forks fully in the shop before I went to the track after applying new lowering techniques to make sure clearance is good. I made over a hundred passes with it lowered as I outlined in my first post.

I am wondering if the external tubes have a taper to them on a busa ?
We've all seen how low pro street bikes are. As I posted above I need to know if the tubes can slide 3 inches and still be able to be clamped by the triples properly. Anyone with a busa could mic their forks or even some pics ? Even by eye a taper should be seen if it is there ?

Thanks guys.

 

[Rainbow7]

The fork tubes (on my '06) do have a taper, which means that I can only have it lowered 1". I don't understand how these guys drop them any further than that.

 

[Commuta_Busa]

there is a taper to the OE tubes. If you were fulltime drag racing and if the rules allow it you can get the bike necked and go with gix1k tubes. This can bring things waaay down.

 

[Fury1]

Hi all.

Thanks for the replies guys.
My '90 gixer fork tubes never had a taper so I could slide them all I wanted.
That leaves 3 options :
1 - Get the steering head cut off the frame and re-welded at a greater rake.
2 - Get the fork inner and outer tubes shortened and use shorter springs.
3 - Switch to gixer 1000 forks and/or forks and triples. Not sure if the gixer outer tubes are the same size (not likely) to fit the busa triples ? If not then whether the bearing sizes on the gixer triples are the same size as the busa neck races (again not likely).

 

[Commuta_Busa]

I just re-read your post... You want a pro street bike. Give Terry a call at Macintosh. He can do a turn key setup or anything in between.

 

[Commuta_Busa]

why do you need to use gix1k forks if you're planning on running pro street? Weight on the front is good and the busa forks are heavier... they'll go low enough and stay within the rules with blocks and a lower triple tree swap.

 

[06+5 bussa]

The fork tubes (on my '06) do have a taper, which means that I can only have it lowered 1". I don't understand how these guys drop them any further than that.

Mine is an 06 also and i know its not much of a difference but my tubes are slid up 1 1/2.