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Dirt Bike Discussions By Brand
Yamaha MX & Off-Road Dirt Bikes
Old early to mid 1970's Yamaha 175cc Enduro
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[QUOTE="lub997, post: 1108454, member: 72793"] If the frame says AT1-#########, then it is a 1969 to 1973 AT1, which is a 125cc bike. If it has a 175cc motor, then it probably has a motor from a 1969-1973 CT1, which is a 175cc bike absolutely identical to an AT1 in every way other than that it is a 175cc cylinder instead of a 125cc cylinder. Every single part on an entire CT1 is exactly the same ast on an AT1 except for the cylinder. The early Yamaha enduros started out with the DT1, which was first released in 1968 and was a 250cc bike. It was so successful that in 1969 they released the DT1 in a lot more sizes, which continued until 1973. The new sizes were AT1 (125cc), CT1 (175cc), DT1 (250cc), and RT1 (360cc). All of these bikes were exactly identical, but just had different cylinder sizes, and different motor parts. Even if your motor says AT1 on it, there is absolutely no difference between an AT1 motor and a CT1 motor except for the cylinder bore, so if it says AT1 on the motor than you have a 125 motor with a 175 cylinder from a CT1, and if it says CT1 on the motor than you have a 175 motor. 1969-71 models: AT1 125cc piston port CT1 175cc piston port DT1 250cc piston port RT1 360cc piston port 1972 models: AT2 125cc reed valve CT2 175cc reed valve DT2 250cc reed valve RT2 360cc reed valve It is important to note that all 1972 models say AT1, CT1, DT1, and RT1 on their serial numbers instead of AT2, CT2, DT2, and RT2, but merely have later serial numbers to differentiate them as being a later year, not a different model code. You will never see a bike that says CT2 on it because even though it is a CT2, the serial number continued to be printed as CT1. The same goes for all other enduro models. 1973 models: AT3 125cc reed valve CT3 175cc reed valve DT3 250cc reed valve RT3 360cc reed valve It is important to note that all 1973 models say AT1, CT1, DT1, and RT1 on their serial numbers instead of AT3, CT3, DT3, and RT3, but merely have later serial numbers to differentiate them as being a later year, not a different model code. You will never see a bike that says CT3 on it because even though it is a CT3, the serial number continued to be printed as CT1. The same goes for all other enduro models. In short, if your Yamaha dealer tells you that you have an AT3 when they look up your serial number, but your frame says AT1, they are right. All AT3s and AT2s said AT1 on the frame and the engine, as there were no changes in the 1972 and 1973 models from the earlier 1969-71 models other than switching from piston port to reed valve, and switching to a gas tank that didn't have a tank badge. All parts are interchangeable from all years as long as you put them on the same size bike, except for the 125s and 175s, in which you can use any part on either size bike for all years, since an AT1 is a CT1 with a smaller bore. All of these bikes are merely the original DT1 with different engine sizes. Starting in 1974, Yamaha discontinued the AT1, CT1, DT1, and RT1, and replaced the AT1 with the DT125, the CT1 with the DT175, and the DT1 with the DT250. The first YZs were modified DT1s. The first YZ WAS a DT1 modified for racing offroad, but it was only used in racing from 1969 until 1973, and did not become commercially available as a YZ until 1974, when the YZ125 and YZ250 were introduced commercially. What you have is an AT1 with a CT1 motor or possibly an AT1 motor with a CT1 cylinder. Are you sure it really is a 175cc motor? If it is, it will say 174cc engraved in the metal on the left side of the base of the cylidner. If it is a 125 cylinder, it will say 123cc at the exact same spot. If you have a reed block, it is from 1972 or 1973, and if you do not have a reed block, it is a 1969-71 model. Hope all this helps. [/QUOTE]
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Dirt Bike Discussions By Brand
Yamaha MX & Off-Road Dirt Bikes
Old early to mid 1970's Yamaha 175cc Enduro
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