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I had an R3 which has a 321cc engine and the top speed is anywhere from 103-110 mph.
Put a GPS on it and report back. Top speeds are one of the most lied about, and misquoted, estimated things known. Makes fishermen look honest. Estimated does not fill in for factual readings.
Wind resistance is the big issue. Some bikes cut thru the wind better. We used to run 250 cc Yamahas with 45 HP to 120.
They had very good full fairings. I will stick with my 45 HP will nudge 100 on a good day, and Saturday night.
As an aside, my 49 HP Norton did 108. Advertised as 120. UK
 

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When it comes to torque, keep in mind that at the end of the day it's horsepower that is the end product of an engine.

With a higher torque value, the engine can generate power at lower engine speeds.

HP = Torque x RPM / 5252

This is also why engines with higher torque values feel powerful as they build power more when there is an increase in engine speed. It is also why an bigger engine usually can build solid power figures without having higher redlines. A smaller engine despite having a smaller torque value can be made to have higher peak power by having much higher redlines, as there is less mass moving.

If you cannot change the torque (which tends to be relative to displacement), you make changes to increase the redline to increase overall power. With a smaller engine, you can likely make a lighter bike and this is why race bikes use engines with more cylinders. By dividing the displacement up, you reduce the mass of each cylinder and to keep the bike's weight low at the cost of peak torque.

It is also why engines of similar displacement but different cylinder counts can make much different power figures. A Ninja 650 makes about 70 HP with a twin, a Daytona 675 makes about 105 hp with a triple, a R6 can make 120 hp with a inline four at their cranks. However, the Ninja 650 makes 48.4 lb-ft, the Daytona makes 53.3 lb-ft and the R6 makes 42 lb-ft, the R6 makes more power but it would be the least street friendly. Granted, the displacements are different, which would explain why the Triumph is able to make the most torque and the Ninja is meant to be more beginner friendly as well.

The issue with having a higher redline is it makes the engine less user friendly which impacts street riding. Which is why larger engines tend to popular in the US, you can get away with lazy shifting. Since the power generation is being made at lower RPMs less noise to deal with while bombing down a long straight road, which we have plenty of.

Larger engines have their advantages but they do have their disadvantages.
 

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"We used to run 250 cc Yamahas with 45 HP to 120."

The R3 is a stock Yamaha making 42 HP and the FIM regulated race bikes make 47 HP.

You need to factor in weight as well.

Heavy rider will weigh the bike down.

Heavier bike with the same power will not be as fast due to added mass.
 

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Post 22. well said.
Post 23. Weight affects acceleration. Resistance or drag affects top speed, especially if the top speed is over 90.
I have run two bikes, same model, same HP. One rider weighs 175 pounds. One rider weighs 120 pounds. Both DT2 Yamaha road race bikes. Side by side. Half mile straight. Multiple attempts.
Another comparison: A higher torque four stroke alongside a higher reving two stroke. Side by side, from a standing start.
The two stroke being riden by the number one plate in Canada in about 1973. Both examples on a track. I am fairly familiar with HP and torque affecting acceleration, and resistance affecting higher speed.

The figure for the R3 I would like is the GPS number. UK
 

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You ask for a GPS figure but then provide anecdotal evidence. In my neck of the woods, it's deer hunting season and the amount of deer has increased noticeably. Most of them are more concerned with chasing their potential mate that they cross the roads without hesitation. I'm not risking my life with all the deer running around right now to satisfy an internet post.

The current R3 in race spec (Here's info on the kit) is currently racing, meaning there are official track results based on its performance.

As you can see below, the FIM regulated R3 which should be making 49 bhp which is 16% more than the stock 42 hp, is capable of reaching speeds of 160+ km/h.

Some racers managed to reach 210+ km/h which is 130+ mph, the average speed is was 142 km/h which 87 mph.

A stock R3's estimated top speed of 118 mph is based on the speedometer, with a 18% margin of error, it would be 100 mph.

Laws regulate that speedometers have to be accurate within a certain error range because they are used to calculate odometer readings.

A margin of error of 18% would be rather high margin of error considering laws in some parts of the world require vehicle speedometers be within 5% of actual road speeds.

A modern day sub 400cc engines are much more capable than you give them credit for, it's not the 1970s anymore.


64421
 

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If it is a track bike, then other methods will be used. Modern times has speed traps and radar guns, and GPS. If it has a full slippery fairing, then it fits in to what I have described above, in clear detail.
I too have wondered in to track bikes to give an example. For the most part tho, the original discussion was about spending money on a smallish street bike to make it go faster. My example of my XS400 fits the bill IMO. I used the GPS and several of my bikes.

Back to tracking speed. We used to have to get fairly accurate revs, and go from there with the overall gear ratio. Many forget to allow about 7% for rear wheel slippage, so get an inaccurate speed. Now and then we could get a larger street bike to run alongside for a speed comparison. However, it is just a number, and not the biggest issue with needing to go fast.

Do you still have the modified R3 and run it at the track. If so, well done.

I also made mention of a modern day 400, and compared it to my 83 XS400. I posed the question above about getting one.
You raise a good point about speedos and OD meters. If the OD is also off, then we are not getting the MPG calculated, or the tyre wear. Some have suggested that a 5% speedo error, does not mean a 5% OD error. My XS400 is the only bike I have that is accurate. UK
 

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Torque vs HP explained

Torque = how quick you get to the wall
HP = how hard you hit it.
 
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My Recent Triumph Rocket 3 Roadster was fun---nuff said.
My Long ago Yamaha V-Max was fun---nuff said.
My not so long ago Buell 1125R Superbike was fun---nuff said.
My long ago Suzuki Bandit 1200S, Yoshimura breathed on was fun---nuff said.
My new Honda Africa Twin Adventure Sports is quick and fun----nuff said.
My 2002 Yamaha 50cc, 2 stroke ZUMA scooter was SLOW and as much fun as the rest---nuff said.

I'd rather ride the torque curve of a BIG engine and not be reving the poop out of some small engine to get every last drop of performance out of it. The sound and feel of a BIG, V-twin engine with a set of Vance and Hines long shots on it, cruising @ 2,500 rpm's in 6th gear is Nirvana!

Sam:)
 

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If you're not hitting the redline every once in a while you are just building up carbon. But you don't keep your bikes long enough to worry about that.
 
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I don't like Antiques like some of you do! :poop:
Sam😁
 

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I don't like Antiques like some of you do! :poop:
Sam😁
I think we like antiques because being antiques ourselves we understand their quirks :)
 
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