have you tried a 4 wheel alighmnent? It sounds like your pretty hard on your machine, maybe you've tweeked the rear swingarm.

 

I am not hard on my DS650 at all, only time I push it is during drag races. I do ride with the RPMs up, due to lack of lowend power.

I measured the circumference of both 20x11x9 razr rear tires today at 5.5 PSI. The left was 62 7/8" and the right was 61 7/8". The left tire was the one that was stretched during bead set. The left tire has a very slight curve to the profile due to the stretching, but the right tire doesn't. It took 9.5 PSI in the right tire to reach 62 7/8"!!! I was able to stretch the right tire to compensate, so now it only takes around 7 PSI in the right tire to reach 62 7/8". The right tire profile is slightly curved now too. I'll try the DS out Sunday if it's not too hot out. I will be checking the rear axle out too this week, since I also have a countershaft wear problem on the inside edge of the sprocket, due to the chain rubbing from some sort of misalignment.

 

Update: When I bought a new set of mud shark rear tires, I had the exact same problem with the rear end. Guess what - one tire was stretched again! There was around a 1" difference in circumference. It was a pain in the neck using a foot pump to stretch the other tire so that the circumferences match. I had to go over 30 PSI to stretch it an inch.

 

Oh great, now I'm gonna have to go check my tires, because I don't think tire circumference is a DS-only issue.

 

Greetings,

As Ridz and others pointed out, this is a common phenomenon in drag cars. The body twist in a Hemi Road Runner or GTX was so pronounced that they built them with an extra leaf in the right (or was it left) rear springs. Which brings up another thing to check -- suspension. Is it evenly matched all around or could something be off here? Just a thought.

 

Cars have a different rotational torque than most motorcycles/ ATV's. On a car, you have an engine crank and drive shaft that spins lengthwise to the vehicle, from left to right, typically. On a motorcycle / ATV, the spin is 90 degrees different, front to back, not left to right. Torque on a motorcycle / ATV will generally "lift" or "squat" the vehicle, depending on the direction of the crank spin, instead of tilt it to one side.

Plus, most ATV's have a solid rear axle with only one central shock mount, so there is no independent travel of the rear wheels, which would let it raise on one side and lower on the other side like a car does from torque. Granted, there is independent suspension on the front, but that shouldn't play into it very much, since the power is being applied to the rear wheels.

Either the wheels are different diameter, or the vehicle is not square from the opposing corners (wheels), either permanently or under power.

Thanks,
CRT_Leech

 

Greetings,

OK, just for the sake of argument, what if the front suspension was uneven -- maybe one shock is weaker than the other. Its going to change the balance of the machine and could affect the traction or footprint at the rear. Also, its going to affect the steering and could affect the running direction as much as a bad alignment. I don't profess any mechnical insight here (is it obvious?), but it might be worth a look.

 

Yes, if the front suspension was uneven enough, it may make the rear weight bias uneven, but it would probably have to be enough that it would be obvious by looking at the front suspension. It would also be noticed on launch and landing during a jump also, since the front corner that was weak would dive on take off and landings to that weak side.

With a solid rear axle, especially one so wide (being wider than the front track), that is going to have more leverage to even out power distribution compared to right-left front weight bias. If one front corner was weak, it would more than likely lower the rear suspension a little, since the leverage applied goes to the center point of the rear suspension, due to centrally mounted rear shock. Or, the reverse may happen and the rear suspension would hold up a weaker front shock if the weight balance were more towards the rear, which it isn't on the DS. This happens in rear engine race buggies with stiff front suspension. The buggy could actually lose an entire wheel and tire on one corner, but still continue to race, because of the light front end, the corner with the missing wheel only touches the ground occasionally. At a dead stop, it could even look like there was a jack stand holding that corner up because it's sitting so high without a wheel.

Good ideas though, laters,
CRT_Leech