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Vintage Rider
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Discussion Starter #1
Back to the Eighties: The Rotary Jets from Yamaha

CC's not years that is! Before putting my bikes into hibernation as well as getting them ready to ride again in spring always gives me a chance to put together a related grouping of bikes. (Last fall I featured the "Ironhead 90's from Honda) The Yamaha ‘80s were actually introduced in 1963 with the street version model YG1. In Yamaha “speak” the “G” referred to the 80cc series bikes that would become Yamaha’s bread and butter series throughout the 60’s. Many slight variations would follow the basic YG1, as advancements in engineering developed. For instance there was a YG1-D which had electric start, then in August of ’64 came the YG1-K with Autolube. Later in ’65 was a sport model with up-swept pipe and slimmer tank called a YGS1. One of Yamaha’s better sellers in the USA was their 80cc Trail bikes, which used a “T” in the model designation.

So I pulled out 3 of my 80’s to show you some of the different styles that were available in ’64 & ‘65. From left to right are the 1965 YG1-TK, 1965 MG1-T and a 1964 YG1. My ’63 first year YG1 version was left in the shop as I thought it had too much patina for this group although complete and original. About the only difference is the ‘63’s have round tail lights and different turn signal lenses.
Here are 3 distinctly different Yamaha 80’s. The first 2 (L – R) are designed for the hunter and sportsman, while the last one is a street bike made for daily city transportation.
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This YG1-TK Trailmaster 80 model was first introduced in late '64 and carried in the line-up into 1967 when it was replaced by the YG5-T in '68. Here's what all the letters stand for..."Y" is believed to mean Yamaha, but that doesn't conform to the "M" used in the step through models. The "G" means 80cc class, the "1" is for the first series, the "T" is for trail and the "K" indicates that it has an oil injection system. Both versions of Yamaha’s trail bikes used 16” wheels front and rear instead of the 17” wheels of the street bike. This helped give more clearance preventing plugging up the wheels with mud.
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Here is my 1965 Yamaha MG1-T, which is going through a renovation and still needing some minor work, mainly a new seat. Frame parts are especially hard to find for this model as nothing matches the other two styles, even though they look nearly identical. This step-through model is referred to as an Omaha Trailmaster 80. Yamaha also had a 55cc step-through model which also used the name Omaha as well, going back to 1962. I'm sure the Honda's step-through trail bikes, with their ease of mounting and dismounting had an influence on Yamaha's copy cat design.
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On the lift getting the battery put back in along with some fresh non-ethanol fuel, is my Yamaha YG-1 80cc rotary valve which were one of the first Yamaha machines that found worldwide recognition and fame. It was sold in very large numbers, and eventually in a few different trims, but commonly called the "Rotary Jet 80". This model helped give the manufacture a solid bottom line as well as playing an important part in keeping Yamaha from failing like so many of the manufacturers did during the early to mid 60's. The early ones did not have the famous Autolube injection system; instead a 20:1 pre- mix was advised. These early pre-mix versions were shipped with turn-signals although not required, as well as fully enclosed chains. Rear sprocket was a 39T while both trail versions came standard with a 51T.
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All three of these models have basically the same engine with the newer versions having Autolube. The transmissions are all 4 speed ball lock style with manual clutch. Yamaha decided not to use an auto clutch version in their Trail bikes, unlike Honda.
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The “center tank” style YG1-TK “Trailmaster” came with Autolube in August of 1964, this 1965 version does not show the factory optional chrome luggage. Yamaha early trail bikes all had low pipe exhaust which seemed to regularly get dented. This particular bike was never taken off road and is in fantastic condition with just over 800 miles on it.
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The Omaha Trail (center bike) was sold in Red, Yellow and White. White is by far the rarest color in which it was sold. None of the MG1-T’s came with Autolube. It was the most economical of the 3 with a price of just $299. Mainly designed for ranchers and agriculture to compete with Honda’s step through CT200 this particular MG1-T has had a rough life and was needing a lot of TLC to bring it back to looking good again. A lot of engine work (including bearings) was required as well as cosmetic. At some point it had also thrown the chain with destroys the fragile and hard to find shift bracket that covers the primary sprocket.
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Premium Member
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The white Yamaha could be mistaken for a CT200 Honda. I have had to put some bike work aside while I build my new cottage. But I will have a place to work on them during the winter months. The CT200, SV1000S Suzuki, and an XS1100 Yamaha are the main candidates. 3 other bikes are running with just the usual work required. But the Triumph Trophy will get repainted next winter.
As always your bikes and pics are great. UK
 

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Retired twice: Navy and as a govt contractor
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Great pictures of your beautiful bikes, you never disappoint.

The Bike Whisperer said:
My ’63 first year YG1 version was left in the shop as I thought it had too much patina for this group although complete and original.
I for one would like to see this one in it's original patina :)
 

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Vintage Rider
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Discussion Starter #4
I for one would like to see this one in it's original patina :)
Here's a couple pics of the '63 YG1 from the day I got it at the swap meet in Davenport and also after I got it home in 2012. I haven't done anything to it except find a tail light lens that was like hen's teeth for the first year round tail light.
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The other red bikes are original paint and were well taken care of. The white Omaha Trailmaster was a very rough bike which I'm just finishing up, still needs a seat and better muffler. It needed a complete engine overhaul and cosmetics. Here's a pic of me working on it during this virus lock down time.
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Retired twice: Navy and as a govt contractor
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12,338 Posts
That is a good looking bike for what 57 years old. Your shop amazes me every time I see it.
 
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