hey, first id like to say hi to everyone, as this is my first post. i have an sdg 107 motor in my crf50, the problem you are having is in fact known with sdg. they have put together an update kit that is "supposed" to relieve this problem. the 2004 models have weak transmissions, everything from jumping out of gears, weak shift forks, bad kickstart shafts, loss of gears etc. you could see one or more of these problems. my bike started to hop out of third for a while. then i got the kickstart problem like you, immediatly followed by a loss of fourth gear (just grinds, with no forward motion), and third gear is like neutral. anyways, they admit the fact that it is a problem that needs to be addressed and that depending on when you bought the bike and where, they will either cover it in full or they will cover just the parts. i ordered the kit, the part number for the complete kit which includes a new transmission, kickstart assembly, rh side crankcase is 111206 you can contact SDG directly at 1 (714) 258 1224 and ask for Harper in parts and warranty. i just bought the kit, it was $199.00 because they told me they would only cover the parts, not the labor. to do this job its like 4.5 hours or so it would just be cheaper to buy the kit and do the job myself. let it be known that they are pretty slow on getting the parts shipped, its been 14 days now and its not here yet.
reply back if you want pics as i do the job, ill post them. as i do this trans repair kit, splitting the cases is needed so at this time, im putting a takegawa superhead 124cc piston kit in. the cases are already bored , just the cylinder needs to be. ill post my results when i get it in. good luck with yours!
