maxpower250r
New member
I sure have enjoyed the TY forum and have learned alot! I recently purchased a 98 srx 700 (only 740 miles on it and I paid $1200...I did good) and am working on getting it dialed in. It was form NY and jetted for sea level (stock) and now its up in Colorado...4900ft at home 8-11000ft when we go to the mountains. According to the service manual you go up on pilots (richer) as you go up in altitude. I'm a 2-stroke atv guy and I certainly have never went richer on pilots to go to thinner air. I'm guessing the jetting chart is correct but could somebody explain this to me? Another question-Its jetted by the book for 8000ft right now and it fouls plugs down here at 4900 just moving it around the shop and loading it on the trailor. I went by the book with br10ecs and am hoping that is the problem. Will br9ecs help me out and be o.k.? thanks.
all the cicuits in the carb work with each other to optimize performance. as the chart shows increasing pilots it probably reduces mains, changes needle height and fuel screw adjustment. the yamaha charts seem to be a little on the fat side due to warranty issues. plugs are cheaper than top end rebuilds. if your fouling out at home, dont leave the sled idling, blip the throttle occasionly or hold at about 2k rpm. lower altitude is leaner conditions. if you jet for 8000ft, dont do any wide open extended pulls at 4900 ft. i have ran the ngk 9 in my 98 since new. there was a service bulletin on this issue years ago. hope this helps.
There was a bulletin to use the BR9ECS plugs, and they seem to help the issue.