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How many HP on the Dyno

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I guessed 14
 

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10 at the wheel


...and I was way wrong.
 

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Discussion Starter · #7 ·
I wonder about just a simple jetting, how that affects a Dyno read. I sure could feel the difference when I got mine dialed in. Especially since Yamaha pushes 'em out the door so lean.
 

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That flat torque line gives it away. It's Not stock.
 

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Surprised test didn't run out to 9,000 rpm or so to see how peak numbers fall off approaching redline.
While not the first Dyno results for a TW reported here I am curious how Blackballs' TW would have fared compared to another "stock" TW200 on a cool day at sea level...might see something like 14hp. vs 11 hp. ( ballpark of previously reported peak HP by other forum members either Dyno'ing their own TWs or reporting published material from other sources).
 

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More informative if they did a before and after. Even just a silly muffler. But yeah, rich up a tad.
We already know 200cc isn’t a platform for raw power but be nice to be reaffirmed as to what changes are really effective or not.
 

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We need to pitch in a collection and have Elime dyno his bike. I would like to see what his mods have done.
 

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I'm still pretty impressed with where 13hp can take me.
This, right here. (I was guessing 12, think I read that somewhere, so not too far off.)
 

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Did you notice the he says this was at 4200 feet elevation? And the temperature also has a large effect on the air density. He said it was "a hot, muggy day" which would increase the "density altitude" (The actual density of the air that is available to power the engine.) to an even higher altitude. (Less dense air, less power.)

The general rule of thumb is 3% power loss for every additional 1000 feet of elevation.

If the temperature was actually as low as 44 F, (7 C) the standard temperature for 4000 feet: (The standard temperature for a given altitude tends to be lower than might be expected. In summer temperatures, density altitude is usually quite a bit higher than the actual elevation.)
(4 thousand feet density altitude) X 3% = 12% -- so 13.0 hp X 1.12 = about 14.6 hp at sea level.

And this assumes he's correctly jetted for 4200 feet - if he's using the stock sea level jets the power loss could be even more. (Although stock TWs tend to be jetted a bit lean at sea level, which means the optimum altitude for stock bike jetting might be somewhat higher than sea level.)

Say the temperature was 80 F (27 C):
4200 feet at 80 F would be a density altitude of about 6500 feet - and high humidity would make it even slightly more.
(6.5 thousand feet density altitude) X 3% = 19.5% -- 13.0 X 1.195 = about 15.5 hp at sea level.

To be a fair test, this should be run at sea level, 14.7 psia, 59 F (15 C) which is considered standard conditions. The carb should be properly jetted for the density altitude it is being tested at. It will probably show quite a bit more horsepower than this test. But then again, as somebody else noted, the engine was probably modified. So this may be an optimistic number for a stock TW,
 

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My 2021 Dyno'ed at 14 last Spring when I did it. Most fun I've had with $75 in a long time! The guys at the shop loved it. This was the subject of an earlier post. P
 

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I read the specs for the discontinued Yamaha AG 200 which wasn't sold here. <interesting little mc imho, btw with some interesting innovations that the tw doesn't have> In that report it stated 16 hp if I am not mistaken.
 

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The old "French Site" also quoted 16 horsepower (11.9 KW) for the TW200. I'm not sure the "French Site" is still around, this was over 10 years ago. If I remember, it had to be translated to English by Google (?), and some of the content was lost in translation. When they referred to gutting out the muffler to get more power, "Muffler" came out trnslated to English as "The Pot".
 
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