Bradley takes to the track!
You know your factory when...
Lowering the oil level in the Showa Big Piston Fork is a simple affair.
Racepak G2X data from the track day shows we've got some work to do.
With the XR all together we ventured out to Buttonwillow Raceway for a Friday open track day before an AFM club race. We sent Bradley out for a few exploratory laps to make sure everything was okay, and after tightening up a couple of things (now we know why Loctite is recommended on practically every XR part) we were all anxious to see what the Harley was capable of. It took just a few laps to see, even from the pits, that the XR is a handful on the track. With Bradley's feedback, we worked on suspension changes throughout the day and gradually got the bike to work better. We eventually found ourselves running out of adjustments on the suspension, an indication that spring or other internal changes were necessary.
As we've seen at the AMA races to date, the XRs wobble at speed on the track, and our bike was no different. Suspension adjustments can makes things somewhat better, but part of the problem is the combination rear engine mount and swingarm pivot. Because the engine is rubber mounted, the swingarm is somewhat free to move around in relation to the chassis. Vance & Hines has released a polypropylene rear motor mount that is legal for the class, and we will hopefully have that installed for the next outing.
All the other modifications to the bike seem to be working fine: The spec Dunlop tires provided plenty of grip and showed nice wear over the course of the day. The Galfer brakes worked well considering they are dealing with 520 pounds of American Iron. And Bradley was comfortable with the hand and foot controls after some adjustments, although we will be modifying the shifting arrangement on the Gilles rearsets slightly.
Back at the shop and after some consultation with David Behrend of Fast Bike Industries, we lowered the oil height in the front fork by 20mm and ordered some stiffer springs for the rear shocks. There are a selection of both straight-rate and progressive springs available, and Fast Bike Industries has supplied us with a couple of options to try.
Our next planned outing is a Pacific Track Time track day at Infineon Raceway, another Friday practice day prior to an AFM club race. Infineon Raceway is the track we plan to race the XR at in the upcoming AMA event, and the track day falls just within the AMA's time limit for practice restrictions - under the rules, AMA competitors are not allowed to participate in any on-track activity within 30 days of the AMA event at that track. There are certain allowances however, and the AMA granted us an exclusion under the rule's "media and promotional activities" clause.
Resources: Dunlop Tires
Fast Bike Industries (Ohlins suspension)
Galfer USA (brakes)
Vance & Hines XR1200 Series