Originally Posted by ferretface
I'm currently riding at around 2500-3000m and have noticed the lack of power (even worse when running high octane fuel# and I was wondered if anyone has tried any quick fixes to make it run better without messing around with re-jetting?
Another guy on a KLR650 has been riding along with me and the "altitude sickness" doesn't appear to affect the Kwakas as much. Maybe something to do with the vacuum type carb on the Transalp - not really sure......
It's okay to re-jet for long term use but I won't be riding at altitude all the time so I need another solution.
I'm going to be heading to higher altitude soon and was thinking of drilling some holes in the airbox #airfilter side# and sticking some rubber grommets in the holes and unplugging them when the bike starts to struggle for air.
Maybe someone on here has another idea or suggestion before I start making holes in the airbox?
From my experience in trips to CO mountains ( 8k ft - 13k ft ) every summer for 30+ yrs. In the 70s and 80s on the old trials and enduro bikes, carbs required dropping the main jet size quite a bit. With the newer bikes with the CV (vacuum) carbs not so much. Each bike is different...KLX300 with CV carb needed a much smaller main jet. Don't remember exactly how much but was supprised how much it took. KLR with CV carb needed very little reduction, 150 to 148. DR350 with CV carb none. And really ran great. All had "opened" air boxes. XR650R with non CV carb went from 150 to 125 main. Don't know how much air box mod will help. You could lean idle fuel screw ( turn in ), might help idle but probably won't effect mid and high rpms much. Some people have reported no problems at altitude. I haven't had my TA up there yet ( next summer
), so I'm also interested to hear what jetting and mods the Colorado TA guys are running. If you're not getting knock or hot running, lower octain gas might help. Hard to tell with the alcohol blend gas we have now. Try to find non blend gas. Makes 3 to 5 mpg difference in my car. Not much way around some loss of power though, short of a turbo.