Air temperature

Hi everyone, quick question and I'm sorry if someone asked it before, but my phone has a hard time searching and on the one search I did I didn't find anything.

Thanks to everyone here (especially Chacal and his incredible patience towards my newbieness), I've been able to make my baby roadworthy enough thati made my way to Gaspesie from Montreal with confidence that I can make it back (I'll let you do the google map work a my phone isn't such a great tool).

Now as I got closer and closer to be sea, the air got colder and colder. Now I know that the air temperature and the barometric pressure have an effect on how the carburetor will work, but I was wondering, is it enough that I should figure out a way to color sync it? It starts after maybe 1 rev of he starter and runs like a champ despite being loaded like a mule, but I've heard horror stories from running too lean. The air is maybe 5-10C colder.

As always, many thanks to all the wizards who help out on this!

 

On a side note: In your face salesman who said it wasn't worth the maintenance! Try and get that cool look and ultimate retroness you meany! Been getting 5-5.5l/100 km on a machine that gets tons of people talking when I stop for gas. Try and get that on a generic looking HarlBMWley!

Though most of the talk involves "You made it from WHERE?!?!?"

 

5C isn't enough of temperature change to matter, and 10C wouldn't matter unless you are dropping in altitude as well. From 0C to 40C at sea level (the temp effect is greater at lower altitudes) the mix only changes by just less than 10%, but going from 40C at 10,000' to 0C at 0' will produce about 20% of change-plenty to lean out. One nice thing typically about going from altitude to the lowlands is humidity typically increases and that helps to richen the mix, it's hard to caculate the humidity effect and most pilots don't bother but it will help level out the change usually. Question is how much altitude drop have you done, and did you balance your mix at your max altitude?

But honestly if it is starting that well and you haven't noticed any other changes like a lower idle or new excessive exhaust pinging upon shut-down, then it's likely your not running too lean. You could and should run a higher octane when at sea level, and lower octane above 5k. You could always do a plug chop and see if you're lean to be sure.

Totally agree about the retro styling and value of our XJ's. They were and ARE great Mbikes.

 

Thanks a lot for the detailed response. I remained pretty much at sea level +/- 100m since starting out, I'll do a plug chop tomorrow just to be sure, but with what you just told me I'm pretty confident.

 

Don't worry about a "plug chop." Just pull the plugs and see how they look. And check the oil. While you're at it, check the air in your tires. (Temp change will affect that.)

 

Spark plus checked! #4 was running a little lean but 1/4 turn fixed that, probably just me color tuning it improperly at home. Now everything is fine .

Oil and tire pressure are checked regularly... Especially oil since she drinks a little at fast highway speed so I have to put some more once in a while. (Another owner of a 1978(?) Honda 750four described it as: stopping for oil and checking the gas. Not that bad in my case XD)