Topping out at 142mph mid 5th gear and gaining nothing in 6th

[RangedKiller88]

I recently bought a new 2019 MT09, put on a M4 slip on exhaust and got a power vision 3. Flashed the ECU raised rev limiter +300, disabled decel fuel cut, disabled speed limiter.
brought it out today to give it a new top speed run cause i thought i had just cut out early the other day at 140. but again today got into it and topped out at 142mph at about 8000rpm rode it out and shifted into 6th at about 9500rpm, but still no gain in speed. was wondering if anyone else has had a similar issue or any tips for what i could do to be able to use all of its power, with a whole gear remaining i should have been able to push judging by the accel rate at least 170...

 

[Otters Pocket]

any tips for what i could do to be able to use all of its power

Simply put, you are already using all of it's power and you have reached the limit.

You have to understand how gearing works - for the increase in speed a gear gives, you have a proportional drop in torque. Because of this, simply adding gears (or changing sprocket sizes) is irrelevant with regards to trying to go faster. To do that you need (a lot) more power from the engine to allow the gears to be used to the full potential.

Combined with the high wind resistance riding a naked bike, the low torque of 6th gear means you simply can't get any more speed out of it, that's simple physics.

The power needed to travel at a certain speed is the cube of the velocity i.e. if you need 10hp to travel at 50mph, you'll need 80hp to go 100mph.

So the power increase you'd need to even push to 150 is huge and to be honest pointless.

 

[bobh]

To get the absolute maximum top speed, ideally you need to do a dyno run to find out exactly at what revs the engine gives maximum power (which is not usually redline revs). Then adjust the gearing so it's doing those revs at your target speed in 6th. That will probably mean coming down 1 tooth at the front and maybe going up 1-2 at the back wheel. That's quite normal practice when prepping a bike for racing.

I've done something similar on my Fazer8, but that was more to improve flexibility at normal road speeds, not to get higher maximum flat-out speed.

 

[Otters Pocket]

To get the absolute maximum top speed, ideally you need to do a dyno run to find out exactly at what revs the engine gives maximum power (which is not usually redline revs). Then adjust the gearing so it's doing those revs at your target speed in 6th. That will probably mean coming down 1 tooth at the front and maybe going up 1-2 at the back wheel. That's quite normal practice when prepping a bike for racing.

I've done something similar on my Fazer8, but that was more to improve flexibility at normal road speeds, not to get higher maximum flat-out speed.

It still wouldn't make much difference because he's already mentioned he's got no push left even though it's not red-lined, which means the bike has run out of power for the gearing - the MT09 makes peak power at around 10k rpm, so the fact he's changed to 6th at 9.5k rpm means the power is there if the gearing will allow. Changing sprockets wont change this, it can only adapt how the bike behaves up to that max point.

Dropping a tooth on the front is equal to adding around 2-3 on the rear (roughly), so dropping 1 on the front in addition to adding 1-2 on the rear cancels a lot of the change out, making only a tiny change in the gears a touch "longer" and as I mentioned, this will also result in a proportional drop in torque, so it all cancels out i.e. he may now be at 9k rpm in 6th instead of 9.5k, but with less power due to the drop in torque, so still unable to get any more push. Also it will take longer to get to that speed now.

In racing the gears are chosen for the type of track i.e. twisty track needing lots of low, fast acceleration at the expense of top speed, or straighter tracks needing longer gearing at the expense of acceleration. Acceleration can be gained/lost and top speed lowered, but not increased past that max point because the bike has simply ran out of power. You can't have your cake and eat it.

I agree the method you mention can 'tweak' the gearing to get the most efficient setup for the way you ride (e.g. faster acceleration for town riding, lower for touring), but changing that bikes top speed is not possible if the bikes not hitting red-line. You might get a couple of mph showing now and again, but probably more to do with tail winds etc.

Chasing a few mph is one thing (frankly pointless), but it sounds like the OP is trying to get vastly higher numbers, which isn't going to happen I'm afraid without making engine performance mods, which will need to be substantial to push a MT through the air at those speeds.