A few questions!

[skatefreak]

Hey there,
Just a few questions really,
bike in question is an NSR125rr.
Firstly i had the back wheel off to change the back brake disk (the previous one although not that warn decided to misteriously warp itself), anywho after putting the wheel back in and the brake caliper back on the bike now has a strange vibration coming from the back wheel...

It feels almost like the bearings are crunching at a pertucilar point in the rotation and as you pick up speed the vib gets a little stronger (can feel it through the pegs/seat and it even makes the clocks shake a little).

Anywho, really disturbing to be honest. I was thinking it could be spacers but oddly enough when the rear break is applied firmly the vibration disapears completely! I could ride with the bike pressed down and a little more throttle but that really wouldnt do the brakes any good.

Any thoughts on that one?


Also just for anyone that may know.

I am hoping to rebuild the engine over winter but the gears are getting a touch sloppy so was thinking of doing the selector forks and or anything/everything that isnt to expensive (maybe clutch and springs as the clutch is a little weak?), the only problem is i cant find prices for anything out there?! What are these things called! Are they pricey?

Any thoughts would be much appreciated.

Best regards

-Jvr

[.....]

Recheck everything again - spacers, disc, wheel alignment and chain tension.

[c_dug]

As above, check the lot again, you don't wan't it coming apart when your riding at any speed.
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[skatefreak]

exactly what i thought.
I am just completely bemused as to how it can completely smooth out when i apply the back break...

One theory i'm thinking is that the back wheel isnt 100% aligned and that the pads are causing the vib but then again, the vib frequency feels very precisely linear to speed...

Will have to have a badger at the bike next week i think...

Cheers

-Jvr

[Mrs Vale46]

I agree with c_dug and joe is it? Just take the wheel out again and check every little part that was removed during the process and put it all back together taking ur time.

Emma-Louise

[Teflon-Mike]

- wheel bearings.
As you suspect from noises.
IF the wheel is wobbling a bit as it turns due to a bearing being 'out' (possible to knock one skew if wheel speendle brutally removed or re-fitted!) then it can run eccentric. wobble will be knocking brake pads as the wheel goes round, then when you apply brakes, it pulls wheel into line and pads are gripping so cant knock.
- Brake Disc
More likely as you have just changed it.
Same sort of thing as wheel-bearings. Disc isn't running true, knocks pads, until brakes applied.
Either new disk isn't true... was it brand new? Second hand from breakers? Or cheapo from China?
Or its not been fitted true.
Did you clean mounting faces?
Did you torque it up in correct sequence(Ie opposite bolts in turn), with torque wrench? To correct torque, (in stages)
Did you loctite the threads?
Did you clean threads before hand?
Loctited threads, will have residue left when fastners removed, always advised to clean hole with tap and bolt with die to remove any residues and corrorsion, so that when re-fitting, you get correct torque, ie pressure on bolt, not pressure on crud in threads!
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