Why are the top speeds not in the 80's. Looks like the have enough HP. Is it because the peak hp is around 6500 rpm and falls fast afterwards. Can't pull past that point in 5th? Would a different cam be the answer? On that peaks closer to 9000 on the raptor? Why is the 650 rev limter so low? Will a different rev box is the 650 much faster? Thanks.

 

Gears ratios, the desert racing DS650 run 17/F, 37/R sprockets and run in the 90's with just a pipe and 22 inch rear tires. The stock DS650 will not make more power above 6500 if you just add a new CDI. To make power over 6500-rpm range will need to add the following CDI box, carb, pipe, cam, HD valves springs and a higher compression piston.

 

Thumpers arent supposed to turn high rpm. Thats the whole point behind them, you see, to get 35hp (just an example) out of 400cc it needs to turn 9000 rpm, for a 650cc engine it only needs to turn 6000 rpm to make the same hp. The lower the rpm the more reliable the powerplant will be, big motors dont usually turn high rpm because the bore and stroke have characteristic that favor lower rpm. You could make a 650 turn 9000 rpm but it wouldnt be as reliable as the 400 turning the same rpm just by the design of the motor.

Heres another example. Hondas (cars here) VTEC in the newer Preludes produces a bit over 200 hp and can wind out to 8000 rpm (I think 8200 actually) before redline. My Mustang makes about 250hp now at around 5000 rpm, if I asked my engine to turn 8000 rpm it would laugh at me, much like I laugh at the Hondas when I smoke them!

The 650 will produce ungodly amounts of torque compared to the smaller engines allowing them to pull a smaller gear, which will give you higher speeds. I wouldnt trade torque for anything in the world, except maybe a Ferrari!

 

The fact is it is simple physics. The HP to speed curve on a graph is a curve up not a straight line, due to wind resistance. Also the sleeker the design the less HP it takes to overcome wind resistance. A sleek design may only take 30 HP to go 70 MPH while a fully fendered may take 40 HP to achieve the same speed. When I had my 440ex I would leave on a DS then it would run me down after a quarter mile or so, then I cut the front plastic and gained enough speed that it was never able to catch me.

 

um im not sure how good you ride butt ive got a race ready 450ex and a slighty modded ds and when i drag the 2 the ds win's every time every were...the honda is never in front..and the honda has cut fenders ..we also switch riders and makes no diff ...you do need to start the ds in 2nd to win ..my 2 cent's

 

What gearing are you running, What carb etc is your has the head been flowed there are lots of varibles I also would be finding a new engine builder. HP to weight is everything. When I run my neighbors 440ex he leaves on me but I run with him and pass him. Then we race up sand mountain and he blows by me. HP to Weight is everything. and the steeper the sand hill the more it effects the DS. Come to Utah and race my neighbors 440ex up sand mountain. You will see. This thing has beaten piped banshees(the true king of the dunes)and piped Raptors.

 

i would love to know where you would go over 80MPH offroad. seriously, there is no point to going that fast. if you go that fast off road, you would crash. if you went that fast in the dunes, you would turn the handlebars and flip your quad. top speed is over rated on quads.

 

Piped Raptor. My buddy has a piped raptor, a race ready Yosh to be exact, and I beat him with a stock DS.

 

The point of the forum is HP to Weight To wind resistance. It all has an effect. I'm not suprised a no fenderd machine has a better topend than a full fendered one. As far as going 80MPH + here we have the salt flats that extend for miles. they are relativly flat and smooth.

 

In reply to bigdodge99:

My brother (Brand new DS 650 stock) and I (Brand new Raptor stock) just had a little drag race last night down a straight dirt road. I came out of the hole much faster, I wheelied he spun some. I pulled out about 2 quad lengths and stayed exactly that distance all the way though fourth gear he couldn't gain I couldn't pull away, very even after the holeshot. I had a new Cannondale Canibal and traded it for the Raptor (too much like a race bike for me). We had the same race with the DS and the Cannondale and once again the DS lost it out of the hole but this time the Cannondale kept pulling away the whole time. I would say the Cannondale was definately the fastest, IMHO with the Raptor and the DS being very close (rider would make the difference).


John "Nocando"

Not being a smart@ss just stating what happened with us. Milage may vary...lol