Can I use a open header on a ys 140 sport? Noise is not an issue. How long does it have to be? I see that they make a cooling header.

No problem. It's a part number YS 0895. Get one from Central Hobbies.

Hey Dave;

Is there an equivalent straight pipe for the 63 ?

Unfortunately there is not. The 63 likes a little backpressure at the exhaust and if you decide to run just the muffler header and a piece of silicone tubing, keep the length about 6" long to provide the backpressure.