Speed limiter removal VMAX Yamaha

With the help of several members and our local dyno shop Sport Tech Cycles we have completed our endeavor of removing the 138 mph top speed limiter. Let’s jump to the results first. A dyno chart tells more than a 1000 words and for some reason seems to be accepted as ‘proof’ in parts of the online community.

Disclaimer: This modification is for off road use only! This write-up is for entertainment purposes only. There are no implied warranties nor does www.yamahavmax.es or its affiliate sites endorse this modification. Changes to the electronics of your motorcycles can be dangerous, void warranty and can be illegal by local or federal law. If you perform this modification do so at your own risk and with the understanding that this might render you motorcycle out of compliance with regulations.



Chart in SAE correction mode


Lets have a look at the details.

The light blue line represents a first reference point for power and speed on a stock 2009 VMax in 4th gear. The line crosses the X-axis somewhere around 136-138 mph

Next is a red line that represents an identical dyno run but in 5th gear – again on a stock 2009 VMax. Speed falls off around the same 136 mph but with a little extra room at part power that reaches over 140 mph. The lack of power would in real world testing prevent it from ever reaching that speed.

Then there is the French bike (again no pun intended). When removing the speed signal from the main ECU, disabling its ability to sense the 136-138 mph limit, it plays dumb. Total lobotomy through the YCCT system (throttle by wire). It simly limits power output to about 50% of stock. The theoretical limit of 164 mph would never be reached, given the lack of power.

Finally, this is the solution that counts. 100% of power and a similar softlimiter as in 4th around 9200 rpm, with the hard limiter cutting it off at about 162 mph. Enough power left to push the naked bike beyond 160? Doubtful. More likely that in real wordl testing the engine runs out of steam at about 155-158 mph.

If you compare the light and dark blue lines you can tell the similarity. Very similar power delivery, same soft and hard limiter only stretched due to the change in gear ratio.


2009 VMax Electrical Wiring Diagram

Track testing seems to validate that with the governor eliminator, bike behaviour and power delivery does not change over stock, only that 5th gear runs another ~1000 rpm (8500 vs 9500) and the resulting addition of top speed.

At this point in time we have not had the opportunity to perform radar testing to measure the true top speed, but a solid [b]155 mph[/b] are to be expected.

Interestingly enough the stock speedometer displays around 154-155 mph at the true 138 mph. The implementation described below would eliminate that gap between display and real speed, a small side benefit (if you don’t care about an extra buffer the speedo gives you by making you believe you go faster).

The overall implementation is very simple. In my case I opted to make it switchable, so I can go back and forth between stock and eliminator on demand (not really as the switch is under the stiletto seat).

This modifications only changes the speed signal that the ABS ECU provides for the Main ECU and display.

This signal can be found on the following electrical chart. It is the white/yellow wire connecting (47) ABS ECU with (30) Main ECU. The wire carries a standard speed signal.


Signal Wire Splice Point


Switch and Speedo Healer under Seat

The solution is a simple frequency divider. For our tests we have used a 3/2 divider – a common speedo healer set to adjust the signal by 30%. (YellowBox) This box could be replace with pretty much any brand speedo healer or a simple hard wired frequency divider. A ratio of about 20:17 would (~15%) suffice to reach the indicated 155mph.

This little box is put inline with the speed input signal through a switch and both are housed under the Stilleto seat in my case.

Be safe!



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