If the dyno runs at a typical 17% loss from crank to wheel HP, that's about 147HP at the crank. At 13% dyno loss, it's about 140HP. Was the factory spec (HP at crank) 144HP? If so, your bike is right in there.
All dynos read differently...... Fast By Ferraci's dyno was infamously "optimistic".
And rear wheel horsepower (torque) is what you measure. To get to crankshaft HP you must do some mathematical assumptions.
Some dynos have software that does that (makes the mathematical conversion to crank HP from rear wheel), some don't.
The question is: Does it make less power than you can use? and does it make smooth power that allows you to ride quickly with confidence? Is the AF ratio good throughout the engine pull from low to max rpm?
If a Dyno is set up correctly, it should not "Measure differently" from another Dyno -- Almost all dynos used for automotive testing are not "Braking Dynamometers" but "Rotational Mass Acceleration Dynamometers"
The way they work is really very simple -- They have a set of heavy mechanically linked "Drums" that the driving wheels are forced against and then you measure how fast the driving wheel(s) can accelerate this rotating mass .. It is then very simple to calculate the amount of energy (In kW/HP/BHP etc.) that your vehicle can deliver to its driving wheels. To allow for a larger span of energy levels most of them also have some sort of dynamic braking system. The delivered energy can be measured and calculated very precisely. (You can calibrate for losses in bearings and other components of the dyno itself.)
In reality you can measure the same thing on a flat level road, by timing a run and knowing the total mass of you and the bike, and by having an accelerometer on board, you can even get the "power curve" - an Iphone has a usable accelerometer built in.. Its no precision instrument, but it will give you an idea-- You need to select a gear where the bike and you can handle a full throttle run without wheelspin or lifting the front wheel too much > (A dyno test IS safer .. 0 )
When testing bikes you have only the rather small area of contact patch between rear wheel and the "drum" so in order to ensure that you get no slipping (i.e. wheelspin) you strap down the bike very hard. This introduces a variable amount of rolling resistance, that will absorb some of the "horsepower" from the measurement, this is hard to quantify, and simply means that you will have a not insignificant error in measured "Rear wheel HP"
The dyno will thus measure how much energy your bike can deliver to the drum(s) - Two different dynos WILL produce different results, and you will also see a variation between multiple "runs" on the same dyno, especially if the bike is taken off the dyno and put back on -- I've personally seen differences of up to 8 kW on a 220 kW Hayabusa dragracer - So, small differences of less than 1-3 kW are only "significant" if they are seen on repeated "runs" - These measurements were done with no "Gearbox and drivetrain compensation" - In its nature the "compensation" will increase the difference seen between for example a "Before and After" dyno test on a "tuning job" -- (By adding 15% to the "difference" for example)
What dynos are really best at is getting the best fuelling tuning and the best smooth power to RPM curves, since they translate directly to smoothness of throttle response and thus the handling of the bike.
We all know that "Top end BHP" and torque numbers are only for bragging rights.. If someone comes along and says: My YamaKaSuki puts down 136 Rear wheel BHP so its more powerfull than your Italian POS with only 128 RW BHP -- Well just ignore it .. A lot of "Horsepower hunting" dyno-tuning really ruins the smoothness of power delivery, usually whti the added "benefit" of a louder aftermarket exhaust system.
My 920 with Arrow decat headers but still using original silencers and Microtec Ecu was set up by Chris at X-Bikes and it did 129 at the rear wheel, I cannot find the original graph to post at the moment.
Well I nearly missed it just wishing Sophia my 910S BRUTALE
A happy birthday built in early 2005 purchased in Feb 2006 ive had her 15 yrs , 13 absolute wonderfull yrs
Still haven't ridden her much in the past yr feeling guilty