From time to time I've had more than a few forum members e-mail me about recalcitrant Superstreets/EZ street vehicles -- ones that are "jittery"-- that run a erratically. Dirty track or wheels and center pickup spring arms that have weakened are sometimes the cause, but I figure most people check and maintain those well. So, when the symptoms are that other vehciles run smoothly but this does not run smoothly and/or it sometimes will not start once power is applied until prodded a bit, then:
The problem is the front axle electrical pickup finger assembly. The photo below shows the front of a bare chassis (this from the vintage like truck , but all body styles have nearly identical assemblies here) and is zoomed in on the offending culprit, the copper contact spring to the front axle. This particular vintage truck chassis had two traction tires (a majority of SS vehicles have one, a very few, none) - so you can understand that electrical contact with the outer rails really rests on the continuity of this spring making good, and constant, contact with the front axle.
What does happen is that, when the car rests on its wheels, as when running, the axle pushes the contact piece upwards a bit. Over time, this contact piece, which is copper, loses its tension - it's not spring steel and it just seems to gradually weaken until and eventually it to keep it firmly in electrical contact with the axle.
Fixing it: The body has to be removed from the chassis. Then, remove the contact (note the two screws). Remove the contact piece, and gently bend the two curved fingers that contact the axle down (about 1/16th inch usually is all) then reinstall. Please note there are several slightly different ways that SS vehciles are built and a few have a small frame that fits over and retains this that the two screws hold down instead of being directly attached to the copper contact, as in this photo, but it's the same fix: I haven't found any way to adjust this without removing the piece and manually bending the pieces. I also always clean the pieces well at this point but I've never found many to show any signs of dirt of grime.
Preventing it: over enough time, the tension that the car axle puts on the this contact when it is running will likely weaken the contact's tension enough to cause problems - I think it is inevitable eventually. However, think about this: leaving the car sitting on the track when not running, or on a shelf resting on its wheels, will do the same, and very likely this activity represents 99% of the time the copper contact piece is under pressure from the axle. And very likely, that is what is done most of the time. What I do is store SS vehciles on their sides, or when I want to display them, put them on small wood pedestals I make that hold them far enough off the ground that the wheel/axles dangle down to the full limit of their vertical travel, minimizing the tension on that contact.
This fixes the majority of "running problems" I have with SS vehciles.
