Eric

http://www.yamaha-motor.co.jp/global/news/.../09/xt660r.html Look like it : 7) Dual exhaust for outstanding torque character and unique exterior styling Adoption of a left-right symmetrical dual muffler (made of SUS material) that draws two separate exhaust pipes from the two exhaust ports and feeds them into the up-muffler (silencer) instead of combining them into one at the head, helps bring out excellent torque characteristics in the low to middle speed range. The 100mm diameter, 500mm long silencer is covered by a highly heat-resistant nylon protector featuring a metallic-looking finish. This gives the exterior styling a distinctive accent point. Meanwhile, a connecting pipe is provided to cancel out the slight pulse difference between the left and right exhaust pipes to help ensure excellent drivability. This system is also characterized by its pleasing exhaust sound, the optimized sizes and pipe lengths of the exhaust system components and the optimized expansion chamber design. SUS is SUS 304 Stainless steel http://www.doctorimport.com/apex-n1-exhaust.html I think as a rule on a dirt bike, if the pipe is not painted with a black heat paint, then it is Stainless!

No problems! Simple fix's that turns the DT back into a fun machine again, long live the 2 stroke, light fast and fun!

Have you a fix yet? If not what year is your bike? If it a 2004 re there is a wire fix for the YPVS If before 2004 a switch in the speedo. However it the YPVS not the pipe that will make the diff, you lose engine speed at between 7 to 8k because the powervalue closes down to stop some of the exhaust gas getting out!

When you say 2004 the following is for the Electric start RE Model! A new pipe and silenser kit will help below 65mph, however the YPVS is set to close above this speed and creates an effect of the engine speed dropping untill you drop a gear. Take the light housing off and find the wire loom, black rubber housing, the indicator wires run into it, you will find a green/black wire that is connected to nothing, get some male connectors for an auto shop with about 2 meters of wire + a ring ended connector (fit wire and connectors, you can press some of them closed around the wire) and run this under tank and air box to the main system earth under the old kick start hole (Now a black rubber blank plate). This connection allows the power value to fully open to the red line some 11000rpm not close at 8000rpm, note is nothing to do with any rev limiting system as one do's not exist, however its upto you how you us the bike once this is done, but 11000rpm is not over the top for a 2 stroke bike in anycase, (use the best oil and change the gear oil often) at least you can enjoy the engine, if you intend to keep it in 2nd for ten mins from the lights thats your problem! I did the wire fix before exhaust and although the Dep made some diff the power valve already added some 20mph, the dep sounds good and makes the bike easyer to lift in the dirt but only added about 8mph!