Can anyone recommend jetting for riding an sy250 at 6-7k and 10k feet elevation? There is also one of those screen type spark arrestors installed, so the exhaust does not flow as freely anymore. I have some upcoming rides at those elevations. Thanks in advance.

Edited August 12, 200620 yr by Brendan

That certainly is a pretty unusual altitude to ride a trials bike. You will certainly benefit from reducing your jetting but I have no idea how far having only jetted for a two stroke riding up to 4000 feet ASL. For that I changed the main jet from a 240 to a 180 (Yamaha TY175).

There was a fellow who used to post on this site from Indonesia who uses his TY250Z for mountain trail riding in Indonesia at very high altitudes. That being the same motor he may be able to give some guidance. I suggest you post in the Yamaha and maybe Techincal Help forums.

It may also be helpful to someone who has jetted a bike for such low density air to know how cold it will be where you will be riding.