I have no experience with the DAX,
But I have to agree that it is worth spending a little more and not getting a GT5.
I'm sold on the 40mm crank, I have 3 of them.
I'm in OZ so I'll be getting another Rock Solid Motor next, it's probably similar quality/price.
I have several Ebay motors, and they always need something done to them to get them to perform properly.
If you want to just bolt it up, and have a good reliable performer, it's probably worth the extra $50.
Not to mention the better fastners, and without knowing the kit, but I suspect some other better quality components.
But the 'guarantee' of a better balanced crank, why wouldn't you.
I don't know anything about DAX, But I get the feeling Roger' Know's what he's talking about.
I like bolth actually the gt5 and the dax...
Now the dax is,more reliable and a slightly larger and better preformer out the box than the grubee gt5, but with that said the gt5 66cc can be made,into,a great racer with a buch of work, take arrow for instance they havea lot of gt5 dedicated motors built for raceing and even fred crmachine man says with,his top end power kit the gt5will make more power with a cylinder deck than other motors with the same top end power pack... It has to do with the grubees differant port map and timeing but if your not planning on a well thought out and well built street racer than well I highly sugest a dax f80 after 5 dax builds I can say they are a lot better out the box
All I do to a dax f80 when I build for a customer is port and polish the jug, deck the head to go from 6:1 comp up to 10:1 comp, and trim the skirt of the piston and make some minor piston ramps , then I port match the intake and exhaust and cut the cat out of the exhaust, tune the carb and add a high flow filter from a brigs and straton. Then I take it out and ride it for around 20 miles or so and make shure its all tunned up and tight. My builds t&ke a ew days but you get more tnan a slaped on motor .. That extra work I do enshures you get a more powerfull higher reving street rat motor that you know is tunned and you wont have to play with to make it runn right. I always recomend they run 32_40:1 mix and sugjest they buy a 40 t rear and a new hub adapter, I tell them it will make the bike even faster lol but its more of a saftey issue than anything as I want them to have a securly mounted sprocket and to help them keep the reves down a little bit at a cruise speed.
Only 1 customer came back and its because he wanted a fancy high comp race head he bought online mounted and the jug decked for proper squish clearance. Since he bought the bike from me I did the work for free.
I buy the dax bottom end and top end and motor kit seperate this way I can work on the motor and build a modified stock street rod as they go together, the motor bike parts kit I like comes with the cns carb and I am well versed on tunning it .