Shaking using front brakes

[Rymax99]

Hi, I recently acquired a 2006 GSX-F 600. The only issue I really have with it is shaking when using the front brakes, it's pretty severe, constant shaking. I've recently found out that the right front fork may have been replaced by a previous owner when it went down on its right side with a GSX-R fork or something. What should I look out for to know what the issue is? I looked a bit on the rotar but can't notice any obvious dis-figuration, is it possible the fork is doing this?

[Xerrith]

Warped rotor maybe?

[92xjunker]

Worn head bearings.

[zuma]

I would stay off it until I had a specialist fix it. Have you ever seen a vid of a bike head shaking? Worse than an 80 mph unicycle.

[Rymax99]

It's not a speed wobble, and it only happens when applying front brakes. I've tested and it happens even when not compressing suspension at all and very lightly using brakes. It's not a side to side shake of any kind, more of a up/down if anything shake, if anything.

[zuma]

I had a wobble in the forks of my ZZR1200 once. Took it in, they replaced the front disk, and I hadn't gotten across town when it started again. I tightened the nut at the top of the triple tree, and it was fixed. The service center at the dealer reinstalled my original disk and refunded my money. I just don't mess with wobbles up front. Take care.

[92xjunker]

. Could be wheel bearings also... any wobble isn't good.

[shpielers]

Couple easy things to narrow it down. Place a known true flat edge and lay it across the rotors at every angle you can, that'll let you know about warpage. Put the bike on the center stand, get the front wheel in the air. Gently turn the bars back and forth. If you feel the slightest catch, the steering stem bearings are likely shot or need re greasing. Wheel still in the air, spin it and look very carefully for wobble. I use the rotor to brake pad clearance as a measure. That can tell either wheel bearings or rotor warpage.

All that aside...Try if possible to verify if you have actually got mismatched forks. That's a dear-god-dont-get-on-the-bike-until-thats-changed thing if it's the case.
Anyone else, couldn't thr forks just need a rebuild? Something internal perhaps binding up? Uneven preload? Just spitballing.

[Kreylyn]

Over heated rotors can cause heat spots to form. This would cause a pulsing when applying the brakes. You can try to resolve by sanding the rotor to remove the top layer, as it's mostly a surface issue... unless the overheating was extreme, and then you will need to replace the rotor.

Krey

[Rymax99]

Couple easy things to narrow it down. Place a known true flat edge and lay it across the rotors at every angle you can, that'll let you know about warpage. Put the bike on the center stand, get the front wheel in the air. Gently turn the bars back and forth. If you feel the slightest catch, the steering stem bearings are likely shot or need re greasing. Wheel still in the air, spin it and look very carefully for wobble. I use the rotor to brake pad clearance as a measure. That can tell either wheel bearings or rotor warpage.

All that aside...Try if possible to verify if you have actually got mismatched forks. That's a dear-god-dont-get-on-the-bike-until-thats-changed thing if it's the case.
Anyone else, couldn't thr forks just need a rebuild? Something internal perhaps binding up? Uneven preload? Just spitballing.

If it happens without compressing forks at ALL, then there's no way it'd be that, no?

Also, any chance the forks from both bikes are the same, I mean if they were able to be used on it..?

[92xjunker]

Yes, worn bearing would show with little effort on the fork as the weight will shift before compression starts. Could also be worn fork bushings.