70s - 80s 2 strokes

[Redbeard990]

I purchased an old film called Road Racers on Duke Video about Joey Dunlop His brother in law Mervin and Frank Kennedy. They keep saying these old bikes go 180mph do they mean Kmph? Were they really getting 180mph out of those old 2 stoke Yamaha and Suzukis?

[Grimly]

https://en.wikipedia.org/wiki/Suzuki_RG_500

[KiwiAlfa156]

I purchased an old film called Road Racers on Duke Video about Joey Dunlop His brother in law Mervin and Frank Kennedy. They keep saying these old bikes go 180mph do they mean Kmph? Were they really getting 180mph out of those old 2 stoke Yamaha and Suzukis?

You must be a young fella...

[Redbeard990]

I am a young man lol. I love the vintage bikes though. I was surprised that the old bikes go about the same speed as modern machines.

[KiwiAlfa156]

Have a look at this if your interested in 70s two-strokes

https://youtu.be/-qKelFmYUNo?si=31GUZ-wZUuLAYJjy

[Grimly]

I am a young man lol. I love the vintage bikes though. I was surprised that the old bikes go about the same speed as modern machines.

It's more that the circuits and roads they're racing on don't allow for the max top speed to be attained, given a long enough straight.
That video of the TT rider up the other day showed his speedo hitting 315kph (195 in Freedom Units), and that wasn't sustained speed - just reached it and had to brake.

[RichDesmond]

I purchased an old film called Road Racers on Duke Video about Joey Dunlop His brother in law Mervin and Frank Kennedy. They keep saying these old bikes go 180mph do they mean Kmph? Were they really getting 180mph out of those old 2 stoke Yamaha and Suzukis?

I remember one of the Honda 500 GP bikes hitting 200mph at Hockenheim. Early 90's, I think.

[storm 64]

Have a look at this if your interested in 70s two-strokes

https://youtu.be/-qKelFmYUNo?si=31GUZ-wZUuLAYJjy

Awesome Podcast with Kevin Cameron. Thanks for posting.

[Rob S.]

For street editions, 1970s & 80s bikes did not go as fast as modern bikes. There are two general measures of a motorcycle's speed, quickness and top speed. Quickness is generally measured by elapsed time (ET) in the standing start quarter mile (drag race) and top speed is self explanatory.

In 1977, when Kawasaki increased the size of their Z1 from 903cc to 1014, it did 12.2 seconds in the quarter mile, and Cycle World declared it the quickest bike they had ever tested. In 2012, their ZX-14R did it in 9.5 seconds, a big difference.

In the late '80s, sportbikes began to top out around 160 mph. Today, because of a 'Gentleman's Agreement' between the major manufacturers, all flagship sportbikes are limited to 186 mph (300 kph).

In 1968, Honda introduced it's CB750 Four, and for the next few years it was tied with the Harley Davidson Sportster for both quickness and top speed (13.3 ET & 120 mph). Then in 1973 the Kawasaki Z1 came out, and all bets were off. It was off to the races. (Choose your own trope.)

Every bike I've mentioned so far is a four stroke. Because they're designed to burn oil, two strokes were quickly disappearing in the 1970s. But the Kawasaki two stroke triples, specifically the 500 ("H1 Mach III") and 750 ("H2 Mach IV") were the most exciting (and dangerous) motorcycles seen on the streets in the early 1970s.

The Yamaha TZ750 two stroke dominated race tracks in the 70s, but I've never seen one on the street.

I prefer the old bikes because I enjoy being able to actually see the engine. And I think liquid cooling belongs in cars.

If you learn about the history of motorcycles, you put a smile on the face of us old timers.

[Redbeard990]

Awesome, thank you all for the responses. I will listen to the podcast tomorrow at work. I’m definitely interested in the history. I’d like to get a 2 stroke for my next project bike. I had googled the TZ750 after the film but those seem to be rare and about 30k so that’s not possible. I have seen decently priced Suzuki GT750 water buffalo engines for about 1k with shipping. I’d like to make a race bike similar to ones in the road racers film. Any suggestions on 2 stroke engines or bike models that are available?

[KiwiAlfa156]

TZ's were over the counter racing machines, never intended for the street. I did however once a long time ago (mid 1970s) see a TZ either 250 or 350 with a headlight parked on the side of of the street. It had to be a TZ because it was a water-cooled twin, and this was well before the RD/RZ liquid cooled bikes went into production. The TZ250s were numerous, the 350 class end in the 1970s, they made a TZ125, and the rare TZ500. The 750 was the big daddy and suitable classes to race them died with the 1970s. We used to watch them race as kids, and it wasn't uncommon for there to be 20 - 30 TZ250/350 on track at the same time, even in little old New Zealand.

The GT750 was a touring bike, and although there was a factory racing version -the TR750- it wasn't a sporty bike. But was when new, and is today used as the basis for cafe racers. There is a lot of information on performance tuning 2-strokes. As 2-strokes were THE motorcycle racing engine from the mid-1980s to 2002 when the 500GP became MotoGP. A lot of knowledge was uncovered by those, who Kevin Cameron referred to, as a 'dying priesthood'. And is easy enough to find. There are some well known books, just google 2-stroke tuning. It's a pretty arcane thing to get into these days.

If you want to see someone obsessed with 2-strokes www.youtube.com/@2STROKESTUFFING

[KiwiAlfa156]

Awesome Podcast with Kevin Cameron. Thanks for posting.

Kevin Cameron, international treasure!

[storm 64]

Horsepower, Chassis, Tires. Horsepower, Chassis, Tires... It's like a dog chasing its tail, it never ends.

[RichDesmond]

Right now there's a TZ750 for sale on Iconic:

https://iconicmotorbikeauctions.com/auction/1974-yamaha-tz750a/

[KiwiAlfa156]

Right now there's a TZ750 for sale on Iconic:

https://iconicmotorbikeauctions.com/...yamaha-tz750a/

Love the 'mufflers' on the end of the stingers. Bet it sounds like Satan's chainsaw.