1970 Yamaha 90 - Wrist Twisters
 
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post #1 of 22 Old 09-29-2009, 03:20 PM Thread Starter
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1970 Yamaha 90

2 stroke streetbike w/ oil injection. Some kind of weird stamped metal clamshell frame? I dunno.
Dad bought this for mom in 75 or 76 hoping she'd ride it. She buzzed around a little then parked it. It's been in a shed since '82 until last month.
It's in pretty bad shape with flaking chrome, etc. I'm going to make it my pitbike. The 6v battery is only for the lights - it runs fine without one.

Lousy cel phone video:
0928091952.flv video by 750turbo - Photobucket
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post #2 of 22 Old 09-29-2009, 06:04 PM
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That looks older than a 1970 - do you know what model it is?

What an awesome cafe racer it would make!

I think I have a few parts for that machine, looks familiar, I can not name the model though and it is driving me crazier!

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post #3 of 22 Old 09-29-2009, 07:45 PM Thread Starter
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hi
I do not know what model it is. The sticker on the neck says mfr'd 12/69.
Is there a way to cross-ref the vin to determine model?

I just googled 1970 yamahas. All these years I thought it was a 90cc 'cause that's what I remember dad telling me when I was a kid. Could it be a fs50 ?


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post #4 of 22 Old 09-29-2009, 08:26 PM
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Check this link. 6th picture down. Looks more like it to me except for the seat.

Seaside Vintage Cycles

'02 Honda 919 - She's the only one for me!

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post #5 of 22 Old 09-30-2009, 04:39 AM
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Me, I think you have a diamond in the rough, what a pocket rocket it could make!!!

Sure does look like the 1970 G6S - I just looked at the parts diagrams and sure seems to be a match.

Looks like there was two seat options - one with a carrier, the other looked sportier, like yours.

I might have a parts and/or service manual for it, I'll try and check.

***Update - I actually have the parts diagrams on a pdf document!!!! I should be able to email it to you***

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post #6 of 22 Old 09-30-2009, 09:19 AM Thread Starter
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I scraped enough crud off it to see the 1st part of the vin is G5 which this site shows as being 100cc. Yee haw.
Compare Yamaha G5 -vs- Hero Honda CD 100 - Bike Comparison, Pictures, Specifications - Gaadi.com India

and checkout this site of old junk, er I mean classics : Collector Motorcycles

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post #7 of 22 Old 09-30-2009, 09:23 AM
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G5 is a four stroke?




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post #8 of 22 Old 09-30-2009, 09:31 AM
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Barn bike, yay! Keeping it in the family, yay!

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post #9 of 22 Old 09-30-2009, 09:33 AM Thread Starter
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this one is definitely a 2-dinger with oil injection on the right side. sounds like a chainsaw.
one ref on ebay showed it as an 80. too funny.

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post #10 of 22 Old 09-30-2009, 09:36 AM
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The reason I was asking is that the link to the G5 stated that particular bike is a 4-stroke. I have a 2-dinger 1978 Yamaha 250 that I need to get road worthy again.




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post #11 of 22 Old 09-30-2009, 12:08 PM
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It's sure looking like a G6S - It was the model after the YG5, thus the VIN reference. I found the two original parts manuals, with specifications - here are a couple teasers for you -

I'm thinking it is like a 73cc engine - 4.45 cubic inches listed, interesting......

Fun stuff
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File Type: jpg G6S002.jpg (44.5 KB, 6 views)

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post #12 of 22 Old 09-30-2009, 03:42 PM Thread Starter
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Quote:
Originally Posted by UJM View Post
It's sure looking like a G6S - It was the model after the YG5, thus the VIN reference. I found the two original parts manuals, with specifications - here are a couple teasers for you -

I'm thinking it is like a 73cc engine - 4.45 cubic inches listed, interesting......

Fun stuff

that's it, that's it!
you're alright - i don't care whan the mods say about you.

I rode it around the yard today. It started with one kick!
I haven't been on it since I was..... 8? It is totally the perfect pitbike.
Back tire won't hold air. I picked up a tube for it.

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post #13 of 22 Old 09-30-2009, 04:01 PM
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Quote:
Originally Posted by gpzTurbo View Post
that's it, that's it!
you're alright - i don't care whan the mods say about you.

I rode it around the yard today. It started with one kick!
I haven't been on it since I was..... 8? It is totally the perfect pitbike.
Back tire won't hold air. I picked up a tube for it.
email me and I'll send you the parts diagram pdf -

It sure would make a wicked little cafe racer replica.

Oh, I'm sure this is not the first time the mods have been wrong - and it will not be the last.......

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post #14 of 22 Old 09-30-2009, 04:11 PM
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Quote:
Originally Posted by gpzTurbo View Post
checkout this site of old junk, er I mean classics : Collector Motorcycles
wow,that guy has some interesting looking machines there.

c 9er
silver,the fasted colour
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post #15 of 22 Old 09-30-2009, 05:57 PM Thread Starter
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Steve - I got the .pdf . Thanks a lot!

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post #16 of 22 Old 09-30-2009, 06:02 PM Thread Starter
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Quote:
Originally Posted by mcdonald919 View Post
wow,that guy has some interesting looking machines there.
no kidding! check out this Yam street tracker : http://www.sportwheel.com/Used%20Bik...s/P1010024.JPG

(res was too high to post the pic)

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post #17 of 22 Old 10-01-2009, 06:10 AM
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Here are a couple pics of the earlier versions -

And one of the 1970 G6-S

Sounds like they called it an 80
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File Type: jpg gs5.jpg (84.6 KB, 3 views)
File Type: jpg YG5T600.jpg (117.5 KB, 2 views)
File Type: jpg G6S_sb600.jpg (117.1 KB, 3 views)

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post #18 of 22 Old 10-01-2009, 02:35 PM
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Here you go -





Also found the following:

Factory Service Manuals:
G5S
G6S
G6S-B

Factory Parts Lists (Diagrams and part numbers)
YG5-S
G6-S

If you need any specifications or instructions, you know where to find the answer.
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File Type: jpg 600RightProfile.jpg (104.5 KB, 38 views)

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post #19 of 22 Old 10-01-2009, 03:02 PM Thread Starter
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I can't believe you have stuff that old. That's impressive.
If I decide to restore it (the potential value probably doesn't warrant it) I'll have one of those service manuals just to be complete but as a pit bike, I think it's good to go. I might blast & powdercoat the handlebars though........

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post #20 of 22 Old 10-01-2009, 07:24 PM
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Quote:
Originally Posted by gpzTurbo View Post
I can't believe you have stuff that old. That's impressive.
If I decide to restore it (the potential value probably doesn't warrant it) I'll have one of those service manuals just to be complete but as a pit bike, I think it's good to go. I might blast & powdercoat the handlebars though........
clubmans

Come tune up time, you'll probably want the manual.

I wonder, ported, piped - could it, would it -

Bust the ton?


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post #21 of 22 Old 10-02-2009, 06:00 PM Thread Starter
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Scary moment

My brother-in-law (the real motor head of the group) just re-did the top end on a rm80 that he got for free. So here's two grown men chasing each other around the back yard on a rm80 and a gs6. As I pull back up to the garage, mine makes a funny sound followed by a brief gnarly-running sound before stalling.
Oh crap - I toasted it, I thought.
Mike pulled the side cover to find the key in the shaft slipped (maybe not the 1st time?) and the timing went screwy.
I won't tell you how we fixed (rigged) it but it's running fine.

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post #22 of 22 Old 10-03-2009, 04:11 AM
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Oh no another project. Awesome.

Give me that XL to make room..........

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