Another project emerges from the garage RZ350

Isn’t there something wrong with that graph if torque and power cross at 7000rpm like that ?

Personally I always preferred the looks of the earlier none powervalve model. Might have something to do with the superfast / super hot girl that rode one with another crowd. Sadly, she was older than me and generally out of my league!

No nothing wrong with the graph, they really have another power band above 7000 rpm – I don’t have a YPVS but I do have a modified 350 LC that would blow off a un-tuned YPVS yet still do the Sat shopping in a High Street, it has with YPVS reed blocks, Part TZ and LC crank that I can rev to 12,000 the original carbs were junketed in the bin as they gave an over rich mixture at 7000 in top gear which was exactly 70mph on Yamaha gearing, these carbs are a standing joke from Yamaha.
 
My understanding is that torque and horsepower ALWAYS cross at 5,252rpm on a correctly calibrated dyno.

On this graph they appear to cross at something over 7,000rpm.

So, I think something is wrong with it.

This has nothing to do with how powerful the bike is.
 
What is 'a correctly calibrated dyno' - they are all comparative with fiddle-factors to make them read sensibly. Primary calibration is usually through use of a calibrated load cell for force measurements. All calibrations should be traceable back to International Standards with appropriate error analyses.
 
The difference between a Yamaha with variable exhaust port height and one without, is the torque characteristic. The road bikes follow a couple of years behind the race bikes. The race bikes became more rideable when midrange power was improved, so went faster. How many dynos give accurate torque comparisons ?
With the older Yamahas in road races, most sensible people waited until the bike was upright and pointed in the right direction before giving it the berries.
 
What is 'a correctly calibrated dyno' - they are all comparative with fiddle-factors to make them read sensibly. Primary calibration is usually through use of a calibrated load cell for force measurements. All calibrations should be traceable back to International Standards with appropriate error analyses.

The 5252rpm crossover point is simply due to the maths used to arrive at a standardised or normalised way of arriving at (what’s supposed to be) a comparative figure.

Al you’ve told us the V Max story before, and one could argue as much as one likes about whether or not the maths are correct. That is a separate point altogether.

And yes, there are all sorts of fudge factors that can be used to lower or boost the final figure. This is also a separate point altogether.

Nevertheless, as far as I am aware, maths that determine the 5252 cross over point are the current norm for RWHP measurements.

So, the point here is: how come / why does torque and HP cross at over 7,000rpm in this graph?
 
The difference between a Yamaha with variable exhaust port height and one without, is the torque characteristic. The road bikes follow a couple of years behind the race bikes. The race bikes became more rideable when midrange power was improved, so went faster. How many dynos give accurate torque comparisons ?
With the older Yamahas in road races, most sensible people waited until the bike was upright and pointed in the right direction before giving it the berries.
Depends if you were still within the 4, 000 RPM power band, or you had dropped out of it, - but I DO get your point!
 
The 5252rpm crossover point is simply due to the maths used to arrive at a standardised or normalised way of arriving at (what’s supposed to be) a comparative figure.

Al you’ve told us the V Max story before, and one could argue as much as one likes about whether or not the maths are correct. That is a separate point altogether.

And yes, there are all sorts of fudge factors that can be used to lower or boost the final figure. This is also a separate point altogether.

Nevertheless, as far as I am aware, maths that determine the 5252 cross over point are the current norm for RWHP measurements.

So, the point here is: how come / why does torque and HP cross at over 7,000rpm in this graph?

I get a bit confused between horsepower and torque. I think 5252 is the conversion factor. I only know the difference between the two when I ride the bike. If the motor is all top end. the required gearing is different form when it has decent power low down. With a TZ350, once it drops below 8000 RPM, you might be in trouble when it comes back on. YPVS was apparently much better. The lap record on Winton was held for about 15 years by a later TZ250, not a TZ350.
Isn't horsepower divided by the revs times 5252 equal to torque ? I doubt an inertia dyno can measure torque. It is the twisting power of the crank, not the time rate of doing work.
 
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It is a fallacy that higher horsepower means a race bike will be better. Ducatis use EXUP to gain more torque. EXUP is probably used to moderate the noise when better valve timing is used. When you lowerthe exhaust port in a two-stroke motor, you get more midrange and as it rises, you get more top end. - Fastercoming out of corners and probably just as fast at the ends of the straights.
 
I get a bit confused between horsepower and torque. I think 5252 is the conversion factor. I only know the difference between the two when I ride the bike. If the motor is all top end. the required gearing is different form when it has decent power low down. With a TZ350, once it drops below 8000 RPM, you might be in trouble when it comes back on. YPVS was apparently much better. The lap record on Winton was held for about 15 years by a later TZ250, not a TZ350.
Isn't horsepower divided by the revs times 5252 equal to torque ? I doubt an inertia dyno can measure torque. It is the twisting power of the crank, not the time rate of doing work.
Was this the v twin water cooled TZ250?

They were MUCH faster than the old w/c TZ350 on account of having several years more development – until the FIM scrapped the world championship class:(
 
Another project emerges from the garage RZ350
Another project emerges from the garage RZ350
Another project emerges from the garage RZ350
 
"With the older Yamahas in road races, most sensible people waited until the bike was upright and pointed in the right direction before giving it the berries."

This bike handles like a razor blade.
 
Looks like a great buy. Raise the exhaust port the width of a nickel while you have it apart, if you didn't already do it! lol Don't forget the Banzee carbs
 
That little lightning bolt is going to be way too much fun...the police will never catch you on that.
Hey!
I've seen pistons that look like that!
There were two of them in my Fiat 850 as I attempted to drive from Philadelphia to Saint Louis.
Actually made it too.
 
That little lightning bolt is going to be way too much fun...the police will never catch you on that.
Hey!
I've seen pistons that look like that!
There were two of them in my Fiat 850 as I attempted to drive from Philadelphia to Saint Louis.
Actually made it too.
They pull me over for doing NOTHING!

I end up explaining:

"well son, back before you were born, SOME motorbikes had 2-stroke engines"
 
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They pull me over for doing NOTHING!

I end up explaining:

"well son, back before you were born, SOME motorbikes had 2-stroke engines"
Uh huh. You were not making any racket or scorching along...you were in putt - putt mode and they busted you for noise or being too old to ride that stinker.
 
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They pull you over and you pull the senior citizen cards on fixed income to get off free! LOL That's my strategy!
Uh huh. You were not making any racket or scorching along...you were in putt - putt mode and they busted you for noise or being too old to ride that stinker.
Actually, the first time the cop was just wrapping up another traffic stop, small town USA, I idled by respectably at half the speed limit, then accelerated to 40mph, the posted speed limit. I watched in the mirror as he began following me, a half mile back, all stealthy & sheet.
Followed me two miles at 40 mph, then lit me up.
"I thought you inspection sticker was expired" which is bs for "I just wanted to go fishing."
(Stickers are on the left, all he saw was the right side of the bike as I went by.)
When his computer told him I was a duly licensed operator, and the bike was legal, and I was older than his Dad, he apologized & went away. 20 minutes roadside, at night, with 50,000 lumens on ya like a criminal..... for riding a motorcycle.
 
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