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| 1978 Yamaha YZ125 Carburetor Tuning https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=28&t=2681 |
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| Author: | Jahimbi [ Mon May 10, 2010 1:59 pm ] |
| Post subject: | 1978 Yamaha YZ125 Carburetor Tuning |
Hello everybody, I'm new to the forum and want to say hi. I also have a question. I have a 1978 Yamaha YZ125 that I have recently restored. It is bored 10 over with new piston/rings. All new crank seals/bearings/so on. When I ride the bike, it has A LOT of power and runs smooth when the rpms are really high. From 3/4 throttle to full throttle, the bike runs super strong. That makes me think that the main jet is the proper size. The problem is, when I run the bike between idle and 3/4 throttle, it doesn't have much power and it sounds awful. It "pops" "dings" "putts" almost sounds like misfiring or something. I'm wondering if I can do some tuning to the carb to make this mid-range a bit better. I know I can make adjustments to the JET NEEDLE, but I'm not sure if I should go more lean, or more rich. I run Yamalube 2-stroke oil mixed 20:1. I was also wondering if i could run a different mixture and be safe. Maybe 32:1? Maybe that would make a difference in mid-range power? My bike smokes like a chimney when mixed 20:1...lol! Any help would be appreciated. Thanks! |
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