Heres a site with good info on various things.
http://www.off-road.com/dirtbike/tech/
The ones I think that are related to 50s are

Spark Plugs
http://www.off-road.com/dirtbike/tech/2002sparkplug/

Tips to save your 50 when you go through the 5 ft deep puddle
http://www.off-road.com/dirtbike/tech/2002drowned/

Make your own stiffer springs
http://www.off-road.com/dirtbike/tech/2002spring/

Valve Adjustment (for a XR650, but same concept)
http://www.off-road.com/dirtbike/tech/XR650ValveAdj/

Trouble Shooting (for MX bikes, but useful info)
http://www.off-road.com/dirtbike/tech/top10/

Wheel truing
http://www.off-road.com/dirtbike/nov...eelTruing.html
http://www.off-road.com/dirtbike/dec...eelLacing.html

And finnaly gas
http://www.off-road.com/rick/gas-tech_part1.html
http://www.off-road.com/rick/gas2/
http://www.dirtbike.com/forums/topic.asp?TOPIC_ID=11945
This last ones is off a different board, and based on the question is AV fuel good for a 2 stroke, but very useful, this site also has great info for tech tips, mainly 2 strokes but very helpful

 

excelent posts X
now i gotta read
thanx X man

 

What else can I do when it gets dark?

 

put flood lights up in the back yard!