I have a 1970 SL 100 thatI'm making a vintage MX racer out of. I raced back in the 70's, mostly on Euro stuff,CZ,Maico etc bu I had a SL100 play bike back then and raced it once in a while. Anyway I am trying to make a cheap, legal vintage MX'R out of this and have got it handling nicely.I have not spent a lot of time and effort trying to get a lot of horsepower but instead working on the weight and handling while keeping with the spirit of the vintage era. I have early forward leading axle front forks which are illegal in the classic but is ok for the sportsman class. I can quickly change the forks to run in the classic but really like the way it handles now and the lack of weight makes it competitive. I really want to get rid of the battery but have not figured it out yet. These bikes will start and run without a battery but won't run well? If anyone out there has a secret for this I would be interested. I run the small spillproof 6V computer battery which works well but I would like to get rid of it altogether and save a little more weight. I will post some pics soon, check it out. thanks , wayne huff My other thumper is a hybrid 77 XS 650 Yamaha. It is magneto powered (modified DT 250) has good lighting, runs great, no battery. It took some engineering (rigging) to do but it works really well. Actually with a set of knobbys I could race it! It's light and 18/21" alloy wheels, but that is another story.