Sigh* Nevermind, people think Im saying that standard forks are bad and usd forks are the only way to go. And yes usd forks are stiffer, yes the unsprung weight is further away from moving parts, and yes I feel that usd forks where not seen on 600s of the 90's is because they believed the cost too high, the demand lacking, and the fork seal tech of the time wasn't good enough to keep from blown seals, however, bikes did have them (see the buell thunderbolt).

I have read as well as heard, discussed and been straight up told by mechanics who work on race bikes, Instructors and people who frequent track days and race days that stiffer forks are preferred, hard to get used to yes, but once they became comfortable with the difference in usd forks they were able to repeatably drop 2 - 3 sec off of their old lap times.

I guess I should through a disclaimer in here then: I know and understand how a bikes geometry and suspension effect each other in acceleration and deceleration, turning slowly and quickly; however, I have never raced a CBR600 F3. So to the OP and whom ever might be reading this in the future, I hope you got the info you needed. I hope that kjohnson gives you that adjustment that helps with steering and doesn't affect the rest of the bike, even if its just a teeny tiny bit. I hope that you realize that Kjohnson knows what he is talking about, but also that I know what I'm talking about.

 

I am not trying to argue here. Far from it. The geometry changes are only part of it. I just want the OP to understand the consequences of using USD forks on a F3. He may be fine with them and I understand that. But wanting to keep the front wheel and calipers will just add headache and cost. I understand most everyone on this forum has a different outlook. To each his own. Both KJ and I have some experience with racing these bikes. We have seen the outcome of such mods. Just trying to give advice from past experiences.

 

When I got the bike I have now,it had USD forks and the rear was dropped to compliment the front.The whole bike was lowered.A 'nose down' F2/F3 won't be stable mid-corner due to lack of grip and will make the bike prone to tucking without warning.

Forks from any sportbike from '99-now are shorter than OEM F2/F3 forks,about 30mm.In the set-up I received mine in,it was a pain to turn.I corrected it with better set up.

We used to have a guy show up with damn near anything imaginable (R1 front end,Hayabusa etcetc) done to his F3 trying to prove your theory.Dude went around the sun to try and get to the moon lol.He admitted that his bike was harder to turn with the USD forks.And he's no slouch of a rider.Threw lots of money/time away.

Well,Duck and I both ruin lots of egos at trackdays on our older bikes and even a few on raceday with WERA.WERA is the standard in club racing.I myself clicked a few 38s at Road Atlanta.On a SS F3.That I built.

You know people who work on race bikes CJardine? Mine and Duck's mechanic is Rick Matheny.That was Rick's motor Jake Zemke put on pole without any sponsors in 2011.

I go fast enough around Barber Motorsports Park on my F3 to qualify for the AMA grid last year.

Checkmate.

I will hand out lots of info,but the front end adjustment and cam timing I won't.It cost me 100s of hours and 1000s of dollars to learn and/or discover.Just about anything else I'll gladly give away.

 

I wonder what the OP's motivation is behind switching to USD forks. Might help if we knew the why then we could suggest the correct what.

 

i changed my forks almost out of necessity... if you look to page 1 and the second reply you can see why... i bought the bike wrecked and the front forks were bent almost at a 45... i went with the 954 front end for looks, and the fact that i found a whole front end for cheap.... and the 954 front end actuallt made the front of the bike TALLER, and i read the 600rr would lower it an inch or two... but i never planned on racing it, i did it for looks and it was the right price at the right time