Yamaha 500 two stroke dirt?

15 replies to this topic
  • lanz

Posted March 10, 2007 - 05:50 PM


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.

  • Vibeguy

Posted March 10, 2007 - 06:26 PM


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.

  • OregonTrail

Posted March 10, 2007 - 06:30 PM


If you can believe it, it turned worse than the MX360!:lol: The 71 TM400 Cyclone was a :applause: !!

  • pantera

Posted March 10, 2007 - 06:57 PM


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."

Posted Image

Here's a video with a bit about one of them:

  • pantera

Posted March 10, 2007 - 07:07 PM


More info:
PRICE (Suggested Retail): N/A
ENGINE TYPE: Piston-port, reed induction, two-cycle
IGNITION: CDI or flywheel magneto
TRANSMISSION: 4-speed, left side shift
CLAIMED WEIGHT: 236 pounds
WHEELBASE: 55.9 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
FUEL CAPACITY: 2.4 gallons
Posted ImagePosted Image

  • lanz

Posted March 10, 2007 - 08:01 PM


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!

  • bake

Posted March 11, 2007 - 06:14 AM


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

  • SFDemo

Posted March 11, 2007 - 04:35 PM


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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  • zig06

Posted March 11, 2007 - 06:10 PM


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.

  • MantecaMisfit209

Posted March 11, 2007 - 06:14 PM


i have a 78 yz 400 which is two stroke (for sale).

  • lanz

Posted March 11, 2007 - 07:00 PM


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.

  • 305

Posted March 11, 2007 - 07:02 PM


I think I heard something about a YZ490 2 stroke?

  • El Marko

Posted March 11, 2007 - 07:06 PM


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.

  • NorCal620

Posted March 11, 2007 - 09:14 PM


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

  • El Marko

Posted March 12, 2007 - 01:04 PM


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.

  • prairiedawg

Posted March 12, 2007 - 05:33 PM


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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