Topic: another question from Colorado: It's high here, should I re-jet?

[JBMorse]

I am on my cross-country trip and have a question about high altitudes.  What I've got is a '71 CB500 with stock carbs and settings, stock airbox with a UNI filter, and a MAC 4-2 exhaust.  The bike is running fine, but losing power as we ascend.  Coming over Wolf Creek Pass in southern Colorado yesterday, which is 8-9000', I could barely manage 40mph in 3rd gear.  The poor bike is well loaded, but back home we had much more power.  I took a quick look at spark plug #4 this morning, and it's definitely running rich.

So I'm wondering what, if anything, to do about it.  I'm fine running slowly over these mountains and leaving the tuning alone, even if I need to clean the plugs every so often.  But, do I risk any damage or problems doing this?  Would it be stupid to try and run it as is? 

Before leaving for the trip, I recall doing some searching here and am pretty sure I found that I'd probably be okay leaving the carbs alone.  We are okay moving slowly through here, I just don't want to overwork and explode my engine!  What to y'all think?
-Jeremy B

[Jerry Rxman Griffin aka MuthaF'er]

If you start jetting then rejetting you won't get anywhere. You'll only be on passes some of the time. Keep a clean spare set of plugs and drop a gear or 2 if you need to keep the rpms up to keep the plugs clean. Running rich will only foul your plugs. Running lean would be different.

[Gordon]

A quick and easy temporary fix is to remove the air filter when you're at higher elevations. 

[murphyslaw]

i wouldn't rejet them.  if you're carb tuning savvy maybe jumping the needles down a clip to see if that helped them run a little leaner.  pulling the filter would do the trick, but knowing what my stock airboxes looked like (full of dust, dirt, grit, etc) i'd say that's a risky move without some sort of screen on the carbs.

otherwise, i agree with jerry, keep a spare set of plugs, try to run higher rpms, and just check them when you can...