The performance around town and through the gears acceleration would be much better with double the bhp, but 15mph more top speed sounds very reasonable to me! People have fitted 16t front sprockets to the KMX to get 90mph, but your going to end up going slower not faster in most conditions if you did this.Īs i said a 15t front sprocket, unrestrictive airbox lid, and a full performance exhaust, along with re-jetting, will give around 3-4bhp, and 5mph more top speed at the red line.

The std gearing is a compromise for this reason, and the high profile and really poor aerodynamics really would count against it at around 70mph. I think you might be forgetting that the KMX125 is dual purpose bike, and has some off road potential. Thats only 20mph more, but the acceleration is far quicker and it would hold a higher speed for longer etc much more easily than you would with 12bhp!

The TZR125L is supposed to do an indicated 75mph restricted or there abouts, in full power 26bhp mode it would indicate maybe 95mph in good conditions. The change from 12bhp restricted to the full power 24bhp version, is about much more than top speed! The extra 15mph i agree isn't a massive top speed improvement, but the rate of acceleration, and the time it takes to get up to high speeds is very much improved. 15mph from double the horsepower is 'not much' in my book. But if you had read it I think you would find that I was referring purely to the top speed, as was the OP. My KMX200 had 2teeth down on the front sprocket, which made the gears really short, but even though the engine wasn't in good health, it was hilarious around town, and wheelies were so easy too!Īctually, i must admit i would call (if you bileve the official figures) doubling the bhp of a bike 'much more' The best mods would be a full performance exhaust system, a modified airbox lid or a KMX200 item, and re-jetting.Ī KMX with the above changes should be as quick as most 125cc sportsbikes, up to 50mph or so, and far quicker at the lights etc. This is easy to increase to 24-25bhp, or more with further tuning.

In full power mode a healthy KMX will make between 20-21bhp at the wheel. The 14t seems to be an off road/road compromise gearing. In full power 24bhp tune, it will easily hit the redline at 80mph in 6th! If you fit a 15t front sprocket then you get about 86mph at the redline, and only slightly less acceleration. The speedo is around 6mph optimistic, or at least it is on the 200 version! Even then down hill it should indicate 80mph, and that is about on the 10k redline with a std 14t front sprocket. MCN got 71mph out of a new KMX125 in 1987 and that was restricted. Yours is obviously down on power and not running right, as you have said it lacks power even in 5th gear, not 6th. The std KMX125 in 12bhp restricted tune should manage 70mph. However don't expect to get much more when it is derestricted.

Kawasaki kmx 125 v max