I run the Dax Gen IV engines on my two fastest and smoothest running bikes, they have the best looking rods in them of all my other china girls, wide bearing surface on top and three holes drilled for good lubrication, both of mine that I have built up now are very smooth running engines and the higher I twist them up the smoother they get, which is just opposite of what my results have been with all the other china girls I own or have had.
Honestly I cant speak at all about how the Grube GT5 compares to my Gen IV dax engines because I have never owner a Grube engine of any type, as with anything you will get some differing opinions on things like this, but I will tell you that today I took my fastest bike for a ride and got a GPS'd top speed of 49.8 MPH out of that bike running a dax Gen IV engine that I did several mods too, it isn't box stock at all but it is a screamer and butter smooth at high RPM's.
I have heard good things about the Grube GT5 engines also when they have the right mods and you are lucky enough to get an overall good one just like any of the other china girl engines, personally I think the engines that dax and Neil aka: motrobicycleracing sells are the best I have seen and used, they have better quality crank bearings than most and the balance and trueness of the cranks are real nice with the ones I have, so I can only testify to my personal experience and I liek the dax Gen IV or Neils Gen V engines very much.
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