It is okay for you or anyone to disagree with my comment, (not a diagnosis).
Besides our extensive geometry database of good and not so good handling motorcycles I base my comments on: All of our customer SM projects , using our good set-up with special triple clamps makes them several seconds a lap better than they went with the basic 17" 'motard set-up'. They tell me "it's like you gave me 20hp".
I have done the motard thing with a personal hotrod yz426, using 17" michelin roadrace rubber. Running very respectably lap times and racing in D Superbike, giving SV650's fits at little talladega. On one occassion I tucked the front at 80mph. crashed my brains out. 86.7mm trail on that particular set-up. I really needed special triple clamps, but I didn't want a dedicated roadracer out of my woods bike. I was just doing it for the fun of it.
Beware Emjayw and anyone else on 17" front wheels on dirt bikes:
Yes, the turn in is quicker, (because you have made the rake angle steeper with the smaller front wheel, and that is a benefit)you will tuck the front wheel at a slower speed and at less lean angle than with the 21" front (because of the loss of trail). fat rubber and all.
As I said previously, straight-line stability is not the problem. Deep lean angles, with tires near the edge of available grip is when it is deficient.
You wont get much warning when the front wheel tucks. It happens so quick.
Have fun and be careful.
'72 BMW R75/5 (Col. Klink),
'02 KTM 400 E/XC,
'05 ktm 125 sx (for sale)
"Hey, are you okay? Can you get up?
I thought you said you could ride"
All the best