I've worked out that the dodgy handling and steering when coming to a stop isn't my badly worn tyres... Rather the headstock bearings seem to be worn and very notchy. I've read that this was a problem with some of the early bikes, due lack of grease applied during factory assembly and I know that due to the oil in the frame the grease around the bearings gets a harder than normal time, but should they have failed at 8000 miles of road riding? I've done literally a day of trail riding in that time. Has anyone had them changed / replaced under warranty?

mine were trouble at around 5>6000 miles unless bike is under warrenty they are not interested. if you use a pressure washer to clean the bike that can remove grease etc. i just re greased mine and they have been ok since

I regreased my at 25.000km, replaced them at 50.000 and regreased them again at 70.000km. All because slow riding in a straight line became difficult. The bottom one becomes rusty even after applying a lot of grease. I think it is the combination of heating up every time (due to the oil) and a bad seal from the bottom end.

I actually regreased them yesterday, without taking out the wheel and forks, only the steering bar and upper tripple clamp need to be removed. Its a 3/4h job in that way.

Niek, give me a quick run down on how you did it without removing everything please!

Support bike on stand with front wheel 10cm from the ground. Remove the bar, remove central nut, loosen upper triple clamp bolds. Remove upper trippel clamp and the central black ring (actually 2 rings with holder). The forks with wheel will drop down. Now you can clean and lube the bottom and top bearings.

Do you have any special tool for central bolts?
How did you tighten them?

I had mine replaced after only 4000km and they were replaced under warranty and I know of a few others as well that have had to be replaced.
There is more to it than just pressure washing your bike or using a degreaser. It's either a poor design or the bearings are poor quality. Yamaha should accept this and fix it.

Thanks Niek, I'll try greasing them up and see how they feel and go from there...

I used a hammer and nail punch, it is not very thight. I fastened it by hand.

I always use water proof grease.

Have a look at this post I did a while back, the Z would be similar.

http://www.xt660.com/showthread.php?p=114085#post114085

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Mods that I have done to my XTX's

My 04 XTX
Stage 1 & 2 DNA filters / Kev fuel mod / snorkel mod / Drilled air box mod / Engine breather mod / Fork Spacer mod / 15w fork oil /
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My 07 XTX
Raptor 700 cylinder 102mm / Modified Crank Case to take a 105mm Raptor Cylinder / 11:1 102mm JE Raptor piston / Stage 1 Raptor Hot Cam / Ported head / Colder Spark Plug / +2mm Throttle body / DNA stage 1 & 2 filters / Modified Air Box / Snorkel removed / Worry Brothers stage 2 filter cover / 6mm & 8mm Bolts Replaced with Titanium Bolts / Recovered seat in Black / O2 Eliminator /

My 09 XTX
59HP at the rear wheel / Stage 2 Raptor Hot Cam / DNA stage 3 Air Box / Carbon Can Exhausts / Modified Exhaust Link Pipes / PCIII With Custom Fuel Map / Wideband Commander O2 Data logger / LCD100 Dyno Jet display & fuel adjuster / 2500 OHM HT lead instead of a 10K OHM XT lead / Extra Coolant Cooler / Protaper Fat Bars / Tail Tidy With LED Tail Light / OKE Protection Knobs / LED indicators / AIS blocked / Modified rear sprocket rubbers / Rear Foot Pegs removed / 09 ECU With 02 Sensor Changed To A 06 ECU / Complete wiring harnes Changed from 09 to 04 / Home made LED resistor flasher / Hole drilled in the fuel tank filler neck to allow quicker filling / Modified Bar End Weights / Progressive front fork springs, 15W fork oil, forks lowered 25mm, used XTR rear links lowering the rear 20mm, rear spring one click stiffer / Changed front & rear guards from blue to black / 47T rear sprocket / Speedo Healer V4.0 / Kev throttle cam mod / Throttle grip mod / The new 2010 O2 sensor mod is out, works a treat, The new 2012 O2 Controller is out, PM me for details

Now ride a 2018 MT09SP ABS + TCS

My KTM 990 SMR Mod book. http://www.ktmsmt.com/viewtopic.php?f=13&t=4946