I ran 17/40 on my stock/piped bike for a while for trails, but 2nd and 3rd were too tall and I had to shift too much. It really made 1st work better on straight up ridges where 2nd was just a littel too tall and 1st a little too low on stock gearing. But the down fall was 3rd beeing too tall and having to downshift in turns so much. Not to mention 5th gear was useless in dunes.
15/40 makes 2nd and 3rd work very well, much less shifting, easy to be where you belong, but 1st gear is hardly ever used. This costs a bit on top, but even with an aftermarket CDI the stock gearing can barely break 8300rpm on a paved road in 5th anyway. play with the gearing calcualtor at Markynark's website - it will show you that there isn't much lost on top in terms of speed from dropping the gearing - finding the gearing combination for your shifting needs based on where you ride is the important thing.
I'm speaking from opinions based on seriously agressive trail riding, GNCC style - how you ride plays as big a role as where.[img]i/expressions/face-icon-small-wink.gif[/img]

 

When I first changed to a 15 tooth front sprocket, it seemed like my top speed in the sand actually increased. I thought that going to a 43 rear might lose speed but it still feels close and I get there sooner.

 

i know going to 15 in the front is faster in the sand because my wifes 16-40 couldn't catah me. the 15-43 isn't as fast on top but it takes a long time for other ds's to catch it.

 

When my quad was stock I ran the 1/8 drags,and the revlimiter would stop me from accelerating before the 1/8 mile @ 73 mph, then I went to 17/40 and the stock revlimiter would stop me from accelerating ,but after the 1/8 mile @ 81 mph. The DS in stock form can pull taller gearing ALL THE WAY TO THE REVLIMITER!! That cannot be said by any other quad! They(Rappy's,preditors,cannondales,400ex,and the Z400) are ALL "wind governed", meaning their STOCK motors Do not have the ***** to pull over 75mph.



Pretty good for a heavy, Dumbo looking, School bus, HUH![img]i/expressions/face-icon-small-wink.gif[/img]






Biggerisbetter.

 

a few weeks ago i went to the coast and there is one flat area and we some times go out and just open up all the machines so i'm flying along and beating ds's banshees suzukis, and all of a sudden flash comes flying bye, turns out it is a banshee the bad part was there was a passenger[img]i/expressions/face-icon-small-smile.gif[/img] i had to smile about that. the taller gears work well on the flat sand, 17-40 not many could run with me on top, but the hill would get me. 15-43 the hill is cool but i run out of top on the flats. now that i have the engine work i'm going to try 15-41, or 17-43 since i already have the back at 43, i've been trying the speed calculater and my wife ds with the 15-42 and 20" tires works great third is rated at 50 mph and fourth will pull if you shift right after the whoops, if not the motor kind of holds steady, the 15-43 with 22" seems to pull better but it is also harder to keep down, i'm going to try 16-43 this weekend to see if i can stay in a better torque range in third gear, i realise this all depends on the hill, but i guess figuring all this out is what makes it so much fun. a few month's ago bigger ask why we were gearing so low and not being able to use first gear, i've started to ask my self the same question, i'm thinking i should be able to hit the same thing in 1-2-3, instead of 2-3-4, and then i would have something left for fifth gear.

 

I just ran the 17/38 comb in the gearing calculator and it is almost identical to stock gearing with 22 inch tires, so I was wondering what difference did you guys feel when you switched to a 22 inch tire, did it help with the tire spin problem???