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

[LowRyter]

this:

Spying and racing and WWII and Communism and Suzuki.  And it gets worse.

 

https://www.amazon.com/Stealing-Speed-Biggest-Scandal-Motorsport/dp/1844259757

 

Edited Tuesday at 01:09 AM by LowRyter

[LowRyter]

Very good read, @docc

 

better than plenty of fiction.

[docc]

16 minutes ago, LowRyter said:

Very good read, @docc

 

better than plenty of fiction.

I had to laugh at your comment, "And it gets worse." 

Makes me think of this Tom Clancy quote:

[LowRyter]

@docc it's a great book, well written.  Actually should be a movie.  IIRC, the expansion chamber, power valve and rotatory valve were invented here...inspired by the V1 rocket.  Betrayal and tragedy are in the offing.  As well as inventiveness with poor resources....

[guzzler]

17 hours ago, GuzziMoto said:

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. 

Heh he.

I got to ride a mates PE400 ( detuned mx for enduros ) and that was a torque monster with quite the Dr Jeckyll and Mr Hyde personality too....

Great times!

 

[Tomchri]

@docc it's a great book, well written.  Actually should be a movie.  IIRC, the expansion chamber, power valve and rotatory valve were invented here...inspired by the V1 rocket.  Betrayal and tragedy are in the offing.  As well as inventiveness with poor resources....

Pulse jet, V1. Don't be afraid of fire and big bangs before she starts.
Cheers Tom.

Sent fra min SM-S906B via Tapatalk

[Lucky Phil]

On 4/20/2025 at 10:04 AM, 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.

Same here. I like Ryan but this time he must have been taking drugs. The road RG500 was nothing like the race bike and the "production RG500" Makoto Suzuki was talking about was the "production" race RG500 just like the "production" version of the TZ250 or TZ500 Yamaha. A full on race bike only for the track and a copy pretty much of the Factory race bikes, NOT some road bike derived thing. As for the seize and you're dead thing well yea but a bit overstated. Just Pre Covid when I was in the pits at the now defunct Phillip Island international classic I was talking to Mal Campbell multi Australian Superbike champion and WSB podium getter who's been racing for a hundred years. He was racing a "production" RG500 at the meeting ex someone quite famous who's name escapes me and they were replacing the 3dr or fourth cylinder on the thing after it had nipped up again. Mal had caught it every time and they kept messing about with jetting. I mentioned that the same cylinder seizing all the time and going silly rich with the jetting for it obviously wasn't the problem so it must be the ignition for that cylinder which is what it turned out to be. Point is Mal was a gun rider and he caught it every time. 

Ryan fort nine turns out the occasional howler that's for sure.   

Edited yesterday at 06:38 AM by Lucky Phil

[gstallons]

IIRC , Montesa had a motocross bike and for a while they had "blooey pipes" . Think of expansion chambers and cut them in half at the largest diameter. i only saw them once in a DB or MXA magazine . I wonder how they sounded and if they did anything at all ? the equivalent to cutting off your exhaust system (on your car/truck about 24" off the manifold ? It's louder so it's better !

[gstallons]

Maybe it was Greeves , I am no longer sure . All I know is , it was ugly !

[LowRyter]

I just saw the Fortnine video.  I see he tells much of the story from the book and mentions it

 

So far as the RG500, never ridding one.  Assume being a street bike that it wouldn't seize up.  

So far as a peaky race bike?  Well, I saw Kevin Schwantz come out of retirement and do a demo ride on his Lucky Strike champion bike at the first MotoGP at Indy.  He nearly high sided it coming out of the last turn.  I can bet it was really peaky.

Edited 13 hours ago by LowRyter