Molly,

Cheers! Bike is a Honda 250XR Tornado. I have learnt about a lot of stuff on the bike, but the carb still looks a mystery to me. I`ll have a look for this fuel screw - and good advice about filter, my bike does indeed have a plastic panel so will remove this when I am finally reunited with bike (next week I hope!).

On a side-note, do you think when this sputtering is occurring it is better to gas it or close off the throttle? Better to drop down a gear and rev it or try to slunk along? Does this cause any damage to the engine or other components of the bike? I did a pass from Argentina to Chile and hit terrible headwinds, throttle fully open in second gear and probably doing 30-40kps!!!



Someone told me about getting the jets changed, but wouldn`t that affect performance when you come back to sea-level?

Your carb will be dead simple. Go on the Tornado forums, find out what riders are doing to gain performance. May be some clues there. Most CV carbs like you've got have a Pilot fuel screw. (sometimes mistakenly called
a Fuel/Air screw or Pilot screw). Sometimes the screw is inset under carb and covered with little tin cover. Pick the tin cover off with wall board screw, small screw driver, turn IN all the way until it stops (do NOT force). Count the turns.
It's probably set about 1.5 turns to 2 turns out. Go in to .5 or 1 turn from fully seated. Should make a BIG difference)

sputtering should not cause damage but if it's cutting out then kicking back in hard ... THAT is not good.
(hard on Crank/Rod) I would down shift and let it rev. Try to find the "sweet spot" where it runs best.

If you plan to stay up high for a while then changing the main jet makes sense. Should not be hard on that bike. But you may get away with simply doing the adjustments I outlined earlier. If they are NO HELP (which I doubt) then you will need to re-jet. Go only ONE or TWO jet sizes smaller. You should still keep the air box OPEN at high altitude, it really will make a HUGE difference in overall running, as will Pilot fuel screw adjustment.

With an open air box your air filter may get dirty more quickly. So keep an eye on it if riding in heavy dust. Keep it CLEAN/oiled or risk ruination of your motor.

Good luck! Ride Early AM, avoid head winds.

By the way, when I was in Ecuador and Peru, I went from sea level to 10'000 feet or more 5 times in 25 days. That is really the reason I want fuel injection as rejetting every time you hit a pass would be a drag