Topic: Yamaha 1973 SC500

[rtbmrgl]

Hello, starting on a new project, Im restoring a 1973 Yamaha SC500.
My first job out of high school I got a job at Yamaha intl corporate headquarters in Buena Park, Ca.
I bought one in '72, one of the first ones. This was my first real dirt bike, the bike got a bad rap but I didn't have any problems.
Im looking for rear shocks also.

[Bankerdanny]

Looks like you have your work cut out for you. But the nice thing about old 2-strokes is no messing with cams and valves.

Have fun.

[rtbmrgl]

Yeah a lot less bolts and nuts


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[rtbmrgl]

Got the engine out, cleaned the frame.
Removing the chain for the engine balancer, it was a bad idea to have a balancer on a dirt bike. You can see by the photo how much the chain stretches and flops, the guide was in two pieces.

[buffalogt750]

I bought a 1974 SC500 in the mid 1980's and turned it into a drag bike. Port work, custom chamber, 44mm Mikuni carb, custom made forged Venolia piston because stock piston would crack by intake windows, no balancer or oil injector, air shifter, higher gearing, typical drag bike low and long chassis. Ran mid 11 second quarter mile times at about 115 mph. Probably could have dipped into the 10's with more experimentation, but I lost interest and gave it to a friend's son who gave it to someone else. Whereabouts today are unknown. It was loads of fun though.

[rtbmrgl]

I bought a 1974 SC500 in the mid 1980's and turned it into a drag bike. Port work, custom chamber, 44mm Mikuni carb, custom made forged Venolia piston because stock piston would crack by intake windows, no balancer or oil injector, air shifter, higher gearing, typical drag bike low and long chassis. Ran mid 11 second quarter mile times at about 115 mph. Probably could have dipped into the 10's with more experimentation, but I lost interest and gave it to a friend's son who gave it to someone else. Whereabouts today are unknown. It was loads of fun though.

Wow thats a cool story, never thought of drag racing the bike.
 I had mine for about 3yrs. I decided to sell it when after riding an enduro in Stoddard Valley near Barstow, it was so cold and windy the tent was half the size it should be.  Afterward I rode a friends '74 250 Pursang and it was so light compared the the Yamaha with the 4 gallon desert tank I said thats it. Found a guy that traded straight up for '74 Bultaco Alpina, the next year I bought my favorite all time dirt bike a new 1976 Bultaco 360 Frontera, it was one of the most expensive bike out there, a wapping $1600, I had two year loan on the thing.

[rtbmrgl]

I got all the bolts, nuts and other stuff zinc plated today, really time consuming luckily I able to do it at work between Smog inspections.(California thing)
here's my set-up

[rtbmrgl]

Painted the frame, cheap rattle can job.
Here's the monster 95mm bore pistons, apparently they ran with oil injection cable broke. Not sure of the concept of oil injection on a dirt bike.
When I bought mine back way back when, took the injector off and ran YamahaLube injection oil 20-1, never had a piston problem.

[rtbmrgl]

Finished, well almost, carb needle and seat leak, kit on its way.
Started on the 3rd kick, brought memories when I owned one.

http://s926.photobucket.com/user/rtbmrgl2/slideshow/Yamaha%201973%20SC500

[buffalogt750]

Really stunning! Great pictures on photobucket too. I think it's crying for a set of thermal flows!

[rtbmrgl]

Really stunning! Great pictures on photobucket too. I think it's crying for a set of thermal flows!

Thanks,
I tried to find a decent set, either too rusty or too much. Ill video tape when it runs, Its has a condenser wired into the CDI box, this was a fix to retard the timing to calm it down a bit and to help with starting. I dont remember there being an issue for me on the one I owned, of course I was 20 and didnt know any better. It would very easily pull 4th gear wheelies (4 speed trans) and long weekend I'd bald a rear tire.

[rtbmrgl]

The beast lives,
Barn shakin', earth movin', children scarin'  500cc two stroke

[Retro Rocket]

Very nice...

[rtbmrgl]

Very nice...

thanks

[rtbmrgl]

1st ride at Prairie City

[scottly]

 I had mine for about 3yrs. I decided to sell it when after riding an enduro in Stoddard Valley near Barstow, it was so cold and windy the tent was half the size it should be. 

Would that enduro happened to have taken place at the Slash-X? I did a poker-run there in the late '80s.
Great video!! Where is Prairie City?

[rtbmrgl]

 I had mine for about 3yrs. I decided to sell it when after riding an enduro in Stoddard Valley near Barstow, it was so cold and windy the tent was half the size it should be. 

Would that enduro happened to have taken place at the Slash-X? I did a poker-run there in the late '80s.
Great video!! Where is Prairie City?

I just looked up the Slash-X cafe, I don't recall the place, but that was the area. It was in 1975 so maybe the cafe wasn't there.
Prairie City is OHV park nears Sacramento CA., they run the Hangtown motocross there.

http://www.hangtownmx.com/Park.html

[HawaiiMike]

Love that sound!

[Eccentric]

Very cool.  Love to hear those big 2-stroke singles.  Inspires me to do something with my 75 MX400B and 73 Husky 400CR 'long term projects'......

[rtbmrgl]

Very cool.  Love to hear those big 2-stroke singles.  Inspires me to do something with my 75 MX400B and 73 Husky 400CR 'long term projects'......

Thanks, a friend has a MX400, going to help him restore. Im fixing up a yamaha 1974 MX250.
http://forums.sohc4.net/index.php/topic,146987.0.html

[MoMo]

    Reminds me of the old Husky and Maico bike single cylinder 2-stroke... Nothing like the smell of Blendzall in the morning ...Larry

[rtbmrgl]

   Reminds me of the old Husky and Maico bike single cylinder 2-stroke... Nothing like the smell of Blendzall in the morning ...Larry

yeah the Blenzall smell, remember that smell in the desert in the morning before race started.
love the smell of 2 stroke in the morning. 

[MoMo]

   Reminds me of the old Husky and Maico bike single cylinder 2-stroke... Nothing like the smell of Blendzall in the morning ...Larry

yeah the Blenzall smell, remember that smell in the desert in the morning before race started.
love the smell of 2 stroke in the morning. 

. .

I still experience the smell as I occasionally bring out my '66 Suzuki S-32 in which I use pre-mix Blendzall.  Also use it in my Echo trimmer

[Terry in Australia]

That is a magnificent bike mate, well done! I'd never heard of an SC500 and I was a big dirt bike fan back in the 1970's, I had several DT250's and longed for an MX250 or 400, but we musn't have imported any SC500's as the only Yamaha 500 dirt bikes I knew of were the XT/TT500's, which were magnificent big beasts too, I had an XT500 and wanted a TT500. Anyway, excellent work mate, good job!

[rtbmrgl]

That is a magnificent bike mate, well done! I'd never heard of an SC500 and I was a big dirt bike fan back in the 1970's, I had several DT250's and longed for an MX250 or 400, but we musn't have imported any SC500's as the only Yamaha 500 dirt bikes I knew of were the XT/TT500's, which were magnificent big beasts too, I had an XT500 and wanted a TT500. Anyway, excellent work mate, good job!

Yeah maybe US only,
If you do a search on the 10 worst dirt bike its on the list, I had three of them. SC500, CR450, YZ490, go figure.

http://www.off-road.com/dirtbike/voice/ten-worst-dirt-bikes-of-all-time-15569.html

I bought one brand new one just out of High School from my first job at Yamaha International in Buena Park
(probably guessed my age by now). It had seizing piston problems when first came out, my bike was a guinea pig figuring out how to fix the problem, I got a few of the first pistons that were modified. I never had any problems

[scottly]

Ha! Loved the top ten worst dirt bikes! One of the neighborhood guys had a TM 400, and it quickly earned the nickname "the Pogo-stick". The motor had a brutal power delivery, but the handling wasn't up to the task, despite Rick's best efforts, which included fitting then state-of-the-art Fox shocks. His brother Ron had a Maico 400, which handled like a dream, but unfortunately it lived up to the common Maico Break-o nickname.

[MoMo]

Ha! Loved the top ten worst dirt bikes! One of the neighborhood guys had a TM 400, and it quickly earned the nickname "the Pogo-stick". The motor had a brutal power delivery, but the handling wasn't up to the task, despite Rick's best efforts, which included fitting then state-of-the-art Fox shocks. His brother Ron had a Maico 400, which handled like a dream, but unfortunately it lived up to the common Maico Break-o nickname.

I remember the tm 400 as one one of the scariest bikes I ever rode back then.   That is, scary in a bad way...Larry