Would like to know who was behind the two strokes expension chambers? or did you know already? Fortnine seems to have that story!

[p6x]

 

[Chuck]

It's a fairly well known story, but Ryan makes it interesting.

[audiomick]

I only got half way through that. Two mates of mine in Melbourne had RG 500s. Both rode hard, and neither of them died.

[Pressureangle]

Could have stuck to history without the political commentary, but fundamentally good. 

Oh, and "The engines are identical" is at best misleading, and at worst, well, misrepresentation. Anybody who's ridden one knows it's not 170 horsepower, doesn't come on like a light switch- in fact, the powerband is much less abrupt than a Kawasaki Triple. Even if every part number in the engine is the same, the pipes and the porting make all the meaningful difference. On most 2-strokes, an hour by a professional and a tailored pipe can add 10-50% to any 2-stroke, depending on era and state of tune. 

[p6x]

17 hours ago, Chuck said:

It's a fairly well known story, but Ryan makes it interesting.

Well, I had never dug into where those expansion chambers came about. All I know, is that I had a Gitane Testi when I was 14 years old, and I purchased the expansion chamber sold by Motori Minarelli for my 49.9cc engine.

I knew the reason and the principle about it, but I never imagined it came from Germany.

[p6x]

16 hours ago, audiomick said:

I only got half way through that. Two mates of mine in Melbourne had RG 500s. Both rode hard, and neither of them died.

The interesting part came towards the end of the video, and has nothing to do with the RG 500.

[gstallons]

I will never comprehend how these pipes on M-X bikes did what they did in the 70s & up. For those that are old enuf. There were a multitude of pipes , silencers , etc. and they were sold throughout Dirt Bike , MXA and every motorcycle magazine published.

[p6x]

3 minutes ago, gstallons said:

I will never comprehend how these pipes on M-X bikes did what they did in the 70s & up. For those that are old enuf. There were a multitude of pipes , silencers , etc. and they were sold throughout Dirt Bike , MXA and every motorcycle magazine published.

This is exactly why they video is educating; because those expansion chambers should be designed to fit a very specific type of engine, targeting a narrow rpm band.

I purchased mine from the manufacturer of my engine, and it was supposedly tuned to that engine type. However, nothing was specified on what rpm range it was designed to work best.

All the guys from my moto club installed those chambers on their bikes, and it now occurs to me, the only certainty was the unbearable noise produced. As to the increased power, no idea....

[Pressureangle]

6 minutes ago, p6x said:

This is exactly why they video is educating; because those expansion chambers should be designed to fit a very specific type of engine, targeting a narrow rpm band.

I purchased mine from the manufacturer of my engine, and it was supposedly tuned to that engine type. However, nothing was specified on what rpm range it was designed to work best.

All the guys from my moto club installed those chambers on their bikes, and it now occurs to me, the only certainty was the unbearable noise produced. As to the increased power, no idea....

While Fortnine did a great job of explaining the fundamentals, the specifics and nuances are very complex. Headpipe diameter and length are the primary indicator of RPM range, but inlet and outlet cone length, end diameters, length between- all affect peak power, power spread, whether there's a smooth transition into and out of the powerband or a razor-thin line between 'on the pipe' and 'off'.  When I raced flat track, every 2-stroke racer who had the skill to tell the difference and the means to acquire them had 3-4 different pipes to choose from depending on track length and condition. 

It's almost like it's rocket science or something. 

[audiomick]

24 minutes ago, Pressureangle said:

... a razor-thin line between 'on the pipe' and 'off'.  ...

I was allowed to ride a TZ 350 one time. Proper race bike, with slicks and all.

No idle, started working at 6,000 rpm, went mad at 8,000, tailed off above 10,000, and just managed to get to 12,000 without any additional gain. Loads of fun, but that was on a track. On the road, it would have been a pain, if not to say completely useless.

[guzzler]

Ha ha 

My CR 125 motocrosser was the same...

Nothing and I mean nothing below 7500 then all 20 horsepower at once thru to 10,500 ...

Doesn't sound like much but it only weighed 80 kilos and I would've been 10 stone wringing wet back then too.

Loved it!

Geez I would've loved to have had a go on a TZ back in the day as no way in Hades I'd fit on one now! 

[po18guy]

Chambers? Cycle World did a podcast a few months ago, picking the jam-packed brain of Kevin Cameron.

 

[Pressureangle]

Who asked recently 'Who is Keven Cameron?' @Lucky Phil or @pete roper ? One of the Southerners I think. This is probably the best way to know, and an hour is hardly enough to begin to know the depth of his knowledge. 

[GuzziMoto]

Two of my favorite two stroke experiences were racing a TZ250, which was a lot like the above mentioned TZ350, and a KTM 440 EXC dirtbike. The TZ250 was the classic two stroke, no power, followed by some power as you rev. Then, around 8,000 rpm it started to make noticeable power. At 10,000 rpm it kicked in and went, pulling hard up to around 13,000 rpm where it was done as quickly as it started. That bike was serious fun on a track. 

My other favorite two stroke was the exact opposite. The KTM 440 was a monster that didn't have to rev to make power. It was almost friendly at idle, but at some point just above idle it turned into a beast. It quickly went from making some power to making massive power. It was a dirtbike, so it didn't have a tach. But it didn't need one. The power was always there. It was a case of too much power being too much fun. I was not really faster on it then I was on my DR350, but my smile when riding it was way bigger. It would plaster a smile on my face the way it yanked me out of corners. It was like the way spaceships hit warp speed or light speed in sci-fi movies.

Expansion chambers can make two strokes deliver amazing power. They don't automatically make for a peaky motor, they don't always means power up top. They can make power wherever they are designed to. Thinking of them as acoustic resonance is a good way to look at them. Depending on how they are designed they can make power down low, in the middle, or up top. 

[po18guy]

8 hours ago, Pressureangle said:

Who asked recently 'Who is Keven Cameron?' @Lucky Phil or @pete roper ? One of the Southerners I think. This is probably the best way to know, and an hour is hardly enough to begin to know the depth of his knowledge. 

It was the legendary shooter Elmer Keith who wrote a book but the title, "Hell, I was THERE!" applies equally to Kevin Cameron.