After much thought and examination, I finally figured out why it is soo hard to shift a Sachs motor under race conditions. On any engine there is what is called 'drop in time'. This is the amount of time, or degrees of rotation under which gear dogs have the chance to engage the next shift. On the Sachs motor the drop in time is represented by the difference in the diameter of the shift key and the width of the slots in the gears where the selector key fits when in gear. This is .5mm! which works out to about one degree of rotation, or next to nothing. I had my gear slots widened to increase the drop in time by a factor of about 10! I also made my own selector keys out of heat treated 4340 with square ends so they don't act like pre-rounded dogs on a normal transmission, to reduce the tendency to jump out of gear if the shifter key doesn't get fully engaged in the next gear. Right now it costs $300-400 to cut the gears(2nd-6th), I run low gearing(11/54) so I never use first gear. I can produce shifter keys for about $40, depending on the quantity. I just raced my 125 at the AHRMA Prairie City Premier/Classic event. Out of about 8 laps of practise and six/ 5 lap motos, I missed ONE shift. Any one interested can contact me at
[email protected] I am having straight cut primary gears produced in the USA, should be done in a couple weeks, finally, only ten sets, $200/set. Thanks, JP Morgen.
Wish I had $200 to spare right now. Sounds interesting.
Lew Mayer
Opened a Sachs engine (lying around for years) the other day, and found it has these gears.
(http://i52.photobucket.com/albums/g8/BobWardlow/PARTS/pen001.jpg)
(http://i52.photobucket.com/albums/g8/BobWardlow/PARTS/pen003.jpg)
JP.
I am in for a set and a fresh selector key, if available, for a fall project.
Thanks.
Victor
[email protected]
Better check with JP. That's a pretty old post, Victor.
Lew Mayer