RE: 1973 DT 3 tuning

73 Yamaha DT 250 discussion forum:


RE: 1973 DT 3 tuning

RE: 1973 DT 3 tuning 
Richard Law said 2005-01-30 05:48 
 
Comission Yamaha Mechanic,1974 to 1980. Bought a new 1973 DT3 at 15 1/2. This bike is MILDLY TUNED, in PERFECT ORDER it flattens out quickly. Timing must be set 3.6 before top dead center. Must have dial indicator, Yamaha indicator holder, and a "buzz box" that changes tone as points open, which allows timing to be adjusted. Cylinder Head must be removed to set timing. Impossible? O.K. the "ADEQUATE" alternate timing method is to set point gap midway between min/max reccomendations. Oh, be sure point faces are clean and when closed have good contact. Remove Carburator, remove float bowl. LISTEN! this carb has main jet in float bowl so there is a o-ring that is on nozzle that MUST be in perfect condition or bike will run rich. O-ring must be replaced with new one. Carb must be clean with STOCK jetting. DO NOT overtighten 2 nuts re-installing carb, seizes slide, ruins carb. In 1973 Premium gas was 100 Octane, now it´s 90, run B9ES plug not B8ES to compensate. Drum Roll to finish. Remove small End Cap in muffler, flashlight reveales plugging/pluged-up "twister-looking" pipe internal. Get long, sharp pointed drift, put 1/2" hole in it or, just as well the whole internal will come out. Reinstall End Cap. IF compression is good, you´re 1973 DT3 will make maximum power. Not impressive but as good as it gets. 360CC RT3 Cylinder WILL NOT bolt up for more power. Have Fun. Richard Law 
 
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