Massive-altitude-change driving question

Hello all,

I'm going to drive from Albuquerque (5,000ft elevation) to Houston (damn near sea level), and I'm concerned about driving lean on the highway for such long distances when I get down in altitude. My bike is properly tuned for Albuquerque's elevation.

Should I even attempt this trip on my bike or are there work arounds? Perhaps giving the engine a little bit of choke at lower altitudes would work best? Would giving it choke threaten to foul the plugs?

Any advice would be hot

 

Get one of chacal's mixture screw screwdrivers (you won't be sorry.) Once you get down to nearer sea level, use it to open up the mixture screws 1/4 turn to 1/2 turn. Do a plug read when you stop for the night to be sure it was enough. Adjust all 4 equally and it will be easy to put back once you return. The special screwdriver makes it so all you need to do is take out the bolt and lift up the back of the tank a couple of inches, no need to disconnect anything. The markings on it make it easy to make identical precise adjustments. I'm going to buy a few more and add them to my bikes' tool kits.

 

Ternk, last spring I trailered my '80 XJ650 from Minturn, CO (8000') to Amarillo, TX. where I rode to Warda, TX (300') and back to Amarillo covering a little over 800 miles. My purpose was to attend a carb clinic. (I trailered my bike because it was snowing in Colorado, otherwise I would have ridden it the whole way.)

My bike runs great at its home elevation of 8000 feet and ran great in Warda. I didn't take plug reading in Texas, but it ran just great.

My bike has factory jetting.

I wouldn't worry about it. Just to ease your mind you might want to take a plug reading every now and again.

HTH.
Jim

 

I just finished a 2,200 mile trip from Fargo, ND through Bear Tooth Pass in Montana through Yellowstone and back through more mountains. I was also a little worried about how that would affect my bike but she ran great. Towards the higher elevations 7,000-11,000 feet I was getting about 40 mpg. The rest of the trip harvested about 50 mpg. I have stock jets and my carbs have never been apart. I do have a K+N air filter, 4-1 exhaust and some after market coils. I agree that checking the plugs for fouling or charring is a great idea. Also listen for pops in the exhaust or pinging from the engine. Running higher grade fuel helps. You shouldn't pass up the ride though. Go for it and have fun.

 

Wow, you guys are great, for sure. I think I'll try to make the run anyways, and it'll be a hoot.

bigfitz, I already bought the screw adjuster tool from chacal, and it is every bit as good as you say it is, but two of my screws are completely seized up and luckily in the correct position for a perfect tune at my altitude. I'm strongly considering purchasing two new carb bodies, seals, and screws from chacal to replace the damage :/

I think I'll chance it, read my plugs at a stop somewhere, and just enjoy.

Thank you guys!

 

A 5000' elev differential is not a significant Issue on My 2 strokes. But 8000' feet is.
I wouldn't worry about in that old Iron Age 4 stroke engine.
A non Issue IMO..

 

I can't say whether it's a risk or not... I threw my carbs away partially to not have to deal with this type of issue... but the one thing I did want to point out is that the mixture adjustment screws only adjust mixture for idle and near-idle conditions. Opening those up is not going to compensate for your high altitude main jet and jet needle. You'll still be running lean under load, which is where it's more dangerous.