Warped front disc

[kev]

Problem: One / both front discs warped as evidenced by pulsation front when braking. Worse at low speed. The front wheel rolls freely and has not been jamming and overheating the disc, (I don't think).
What I think I have to do is fix a micrometer to the front forks and set it to the disc to determine which disc is warped. Does anyone have this tool that I could borrow. Would you like to show me how it is done or is it straight forward. I can get a disc for $300 plus pads, so I would like to be sure the disc is warped before I replace it. Anyone with other ideas please feel free to comment. The bike is 1988 K100RT with 42,000km.
Cheers
Kev

[bwanainoz]

Is the pulsation you are referring too a shudder in the front end when braking?? or is there a grabbing effect when you apply the front brakes?? have you removed the calipers to see that there are no stones, dirt etc caught in the pad area, that the pads are not overly worn, that the bolts holding the disc and calipers are tight and when did you last change the brake fluid. A few suggestions that may help - and I do not have a micrometer. Cheers

[kev]

Thanks Bwana, yes the fluid has been changed, no there are no foreign objects, yes there is a pulsation consistently matched to the speed, no it is not a grab, no gross abnormality in the disc wear, as it is a relatively new problem, yes mechanically correct. Thanks for those suggestions, it narrows down the diagnosis a bit. I heard that an overheated disc can warp if the calipers are locked on and cause uneven cooling down. This however doesn't seem to have occured here. Typically the warranty would have covered this had the company honoured it, but alas they failed to be honurable, so my bike, my problem. I'll get by with a little help from my friends!
Kev

[geoffcnc]

Kev,

Warped front disc....matches the r.........

I have a micrometer here at my office (Willetton) and some magnetic bases etc, I am sure we can rig up something. Happy to help, despite it being a water-cooled bike. Let me know.

0407 542440

Geoff