When I take off in first gear spinning the rear tires during a drag race on a dirt trail, the rearend is pulling the DS to the left. When I apply the rear brakes at the end of a drag race on a dirt trail, the rearend of the DS will not stay straight - the DS starts to rotate clockwise. I try to keep the tire pressure the same for both rear tires, but I still have this problem. When I go off a jump accelerating as I launch, the DS goes off the jump at an angle. If instead I gain some speed up to the jump and let off the gas instead of accelerating off the jump, the twisting in the air is not as bad or doesn't happen.

You might try taking a little air out of the left tire to compensate. Or maybe it is the other tire to reduce pressure. Trial and error might be a good idea for this problem.

This sounds a lot like what we talked about earlier, Scoob. Regarding the rear axle. Seeing that it's posi traction / straight axle, I don't know why the bike would kick one way or the other. Take a close look at the tires, ensure the pressure is correct, and there are no abnormalities in either of them.

Perhaps bent swing arm or frame too.
BTW, www.bombardierds650.com is going to try and post the microfishe for the DS! That will help us all regarding disassembly.

I thought about this all night and come up really nowhere. My bike has always moved left under hard acceleration when I got good bite and left on two wheels,so I don't think mine is a bent frame because it has always done it.I'm also pretty sure it is not rotational torque ( like a drag car) because the rotation is inline front to rear.
If i'm wrong about that someone speak up ( my degree is electrical not physics)

I don't want to insult anybodies intelligence, but here goes. You need to check all the bearings in the swingarm pivot area and the rear axle carrier. There have been a few burned up carrier bearings at the local dealer. Just a little play in that area would cause your problem. If it is not that, swap your rear tires from side to side and see if the problem switches sides also. I have only heard of this happening once. When a tire was being inflated the bead wouldn't seat. They inflated it to 50psi and it stretched the tire out. Even when inflated properly(same psi) it was a little softer and caused what you are describing. Good luck.

Is the chain and spocket on the left side of the axle?? Do you think because they are on that side that there is more torque going to that one wheel/tire?? just a thought.

ridz those are all good points, but I had the problem from new and everything was checked as far the rear bearing problem.Of course there is always something unknown. I also had the same pull after I installed paddles. You are also correct on the possibility of tire growth, many racers overinflate one tire to stretch for stagger (flat track) after you stretch the tire you deflate and reinflate to a good lower pressure for optimum contact patch,and correct tire stager. I didn't even think about measuring circumfrence so good catch.
Also if the sun shines on only one side of the bike you could get thermal expansion, there is a device that can be installed to maintain a set pressure and most racers use nitrogen as it has more stability through a range of temp. than air.
if all that doesn't fix it it ain't broke( I wish)
thank you once again for kick starting my brain maybe scooby can get his ironed out.

This is a tough one, I'm stumped. Since it did it with paddles also that would eliminate the tire problem. I will keep thinking about it and if something jumps at me I'll let you know. Maybe if you try it on asphalt it will be more exaggerated and that will help you diagnose it. Have you had a partner ride behind you to see if anything is moving the wrong way?

I am not really strugling with the problem I have been able to correct with weight transfer,and I think scooby is having problems stoping and twisting before a jump. Now there is another thing, most cars I have been around with a spool (live axle) tend to move left more often than right, again I DON'T KNOW WHY

I do think I have one tire that is stretched. Discount Tire overinflated one to set the bead. This may or may not be the only problem.