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lanz

Yamaha 500 two stroke dirt?

16 posts in this topic

Anyone ever hear of a Yamaha 500cc two stroke single cyl dirt bike? I thought they made these in the 70's or early 80's. I think they were just like the DT360 except bigger. I have not been able to find any info on them even though I remember a friend had one.

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In the early to mid 70's, like 73-74 Yamaha made the SC500 MX bike. What a widow maker! I had the distinct and very scary experience to ride one in the late 70's Something like 50+ horsepower with the powerband of a 125.

People often talk about the TM400 Suzuki which was tame compared to the SC500.

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It was voted as one of the 10 worst bikes of all time.

"YAMAHA SC-500 SCRAMBLER. Another four-speed brute, this 1973-'74 two-stroke single ran hot, detonated fiercely, stalled constantly and seized regularly. After testing the bike, I noted: "It's gray and black; so is a turkey." Brutally fast, the SC-500 was cursed with state-of-the-dark forks and a pair of chromed shocks that would have faded on a busy barroom door. It shook its steering head like a dog coming out of a swimming pool and the rear end hopped around like the frame had a hinge in the middle. All things considered, the only thing this bike did right was not leak around the gas cap."

7q.jpg

Here's a video with a bit about one of them:http://www.youtube.com/watch?v=BZ76aiC-WOY

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More info:

YAMAHA MX SC 500

PURPOSE: Racing

PRICE (Suggested Retail): N/A

DISPLACEMENT: 496cc

ENGINE TYPE: Piston-port, reed induction, two-cycle

IGNITION: CDI or flywheel magneto

TRANSMISSION: 4-speed, left side shift

CLAIMED HORSEPOWER : N/A

CLAIMED WEIGHT: 236 pounds

WHEELBASE: 55.9 inches

GROUND CLEARANCE: 8.8 inches

FRAME: Tubular, double cradle

FRONT SUSPENSION: Telescopic forks/Yamaha

REAR SUSPENSION: Swingarm w/Yamaha shocks (reservoir type w/adjustable damping)

FRONT TIRE: 3.00x21 knobby

REAR TIRE: 4.60x18 knobby

WHEELS: Alloy

FUEL CAPACITY: 2.4 gallons

INSTRUMENTATION: None

COUNTRY OF MANUFACTURE: Japan

YamahaMXSC500.jpgsc500_74b.jpg

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The guy had one that had transmission trouble. It would randomnly drop in first gear while running in neutral. The guy kept it in his barn and one day in his barn he tried to start it and it flodded. He finally got it cranked and opened up the throttle to "blow it out" Well, you guessed it.. it dropped in first gear! Dam thing pulled a wheelie with him on it and smashed right through the barn doors! Busted his ass, wood boards flying everywhere! His grandpa was sitting on his rockin chair smokin his pipe and he nearly fell out of his chair laughing ! Funny!

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I had one back in the day, it was a handful and we only lasted 1 season together.

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I race the vintage class, and they hot ticket for one of those is the TY wide ratio 5 speed with a PVL ignition, it stops the seizing and makes it run reasonable, especially with the heaviest flywheel available. Updated shocks and forks, and you have a winner!

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Didn't Yamaha have a bike "back in the day" that under the wrong conditions, it would back fire as you were kicking it over. But then it would actually keep running, but in the wrong direction!?!

Sort of made the starting line more interesting that normal.

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I remember the exhaust port was so big the piston ring would fall out and seize the engine. Someone made a sleeve with a split port, basically split the port in two and it solved that problem and they were reliable from then on, they say it did not affect the power.

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I think I heard something about a YZ490 2 stroke?

Oh come on, the YZ490 was around for years and was Yamaha 's last open class bike until the 400 Thumper. Still kick ass bikes. You need to go to an AHRMA national and watch some of the cool old bikes.

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my 490 has earned the nickname "The Sieze King" sucker has stuck no less then 4 times in one year, this is before I knew about crank seals so I guess it wasnt the bikes fault

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my 490 has earned the nickname "The Sieze King" sucker has stuck no less then 4 times in one year, this is before I knew about crank seals so I guess it wasnt the bikes fault

It has crank seals?

Seriously, a 2-stroke engine is just a giant air pump, so if there are leaks, you'll have problems.

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Thumper Talks own Eddie Siseneros has one of these beasts. It isn't nothing like the POS I owned. He has all the tricks done to his and it is one helluva bike now. prairiedawg:thumbsup:

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