Carb tuning for altitude?

[bmc5733946]

Anyone have any advice for a novice at altitude? 1989 MILLE GT stock motor and carbs, lower needles one notch? and readjust idle mixture? Traveling out west, Rockies from MI doesn't run real well and only at 5000 ft. so far.

Brian

[Vasco DG]

You'll always drop performance with altitude unless you're using forced aspiration but to a certain degree it will self correct if the carburettor is set up right in the first place.

Having said that needle and idle mixture tweak will probably do the job unless you are planing a long, full throttle run across the high plains. I never did anything to my 'Vert when travelling in the Rockies and it never choked up or fouled a plug even.

Pete

[Chuck in Indiana]

I never had a problem with the Lario in the mountains, even above 10000 feet. Maybe a little rich, but ran fine. Dunno.. maybe yours is set up too rich at sea level?

[Rich A]

You might also check and make sure your air filter is clean.

Rich A

[rodekyll]

How come none of the carbie exspurts from that carb v efi topic have wandered by to solve what must be a very simple question?   ???



Me, I wouldn't worry about it unless I plan to spend a lot of time at those elevations.  If you're just passing through, be sure your general state of tune is good and remember that you don't spend a lot of time on pure main-jet -- some folks I ride with just turn out the idle mix screws 1/4 turn.  When I ran carbs on the Convert I didn't adjust anything for altitude.  I did however do a lot of adjusting for attitude.   :D

[Ted N]

My bike came from Miami. I live at 7000ft and most rides go up from there and I have not done anything to the carbs in the last 30,000 or so miles since I got it. Runs fine but less power the higher you go, there is still plenty to haul a loaded sidecar and full bags to 12 or 13,000 ft.  Just ride it!

Ted

[Chuck in Indiana]

My bike came from Miami. I live at 7000ft and most rides go up from there and I have not done anything to the carbs in the last 30,000 or so miles since I got it. Runs fine but less power the higher you go, there is still plenty to haul a loaded sidecar and full bags to 12 or 13,000 ft.  Just ride it!

Ted

Yeah, but.. he says it's not running well at 5K. Normally, yes, it's not a problem to go to altitude without changing the settings. I'm thinking it is too rich at sea level.. maybe the needle position?
Why?
Weak ignition problems can be masked by rich mixture..and the carbs might not have stock settings. just a WAG.

[bmc5733946]

Thank you all for the help! The bike is mostly stock but has a euro jetting kit from Moto International so may be a little rich to start with.
I have had to reset my trip, left my bike with stepson in Firestone CO, rented aToyota Corolla for the western end of my trip. I just couldn't handle the cold and wet, cold yes, wet yes, the combination was to much for me. I am dissapointed but not discouraged. I have some experience with the dangers of hypothermia and I am no hero. Wisdom comes with age, prudence with experience.
Again thanks for the help!

Brian

[pressureangle]

How come none of the carbie exspurts from that carb v efi topic have wandered by to solve what must be a very simple question?   ???



Me, I wouldn't worry about it unless I plan to spend a lot of time at those elevations.  If you're just passing through, be sure your general state of tune is good and remember that you don't spend a lot of time on pure main-jet -- some folks I ride with just turn out the idle mix screws 1/4 turn.  When I ran carbs on the Convert I didn't adjust anything for altitude.  I did however do a lot of adjusting for attitude.   :D

[bmc5733946]

Just wanted to update this thread!
Some of you might remember that I left my bike in Firestone, CO because of weather at the higher altitude passes I would have to go through to get to Yosemite. I returned to Firestone and picked up my bike at my stepson's house and started my ride home to MI. The bike was running as poorly as it was when I arrived in Firestone. didn't fix itself while I was away. I looked at many things including removing the float bowl to see if maybe the idle jet had come loose, looked at the points, thought about condensers etc.
I purchased some new spark plugs and installed one on the right side where the plug was sooty and probably fouled, saved the other three for later, it ran better so I headed for home. It still wasn't right but was rideable at about 4,000 rpm. I continued to think about the problem and took another look in Chillicothe, MO, even pulled the tank again and cleaned the points with emery cloth and regapped, another new plug on right and one for left too. I was working on it at a Car Quest store around time for the day shift going home, the machinist took an interest in an old geezer on an old Guzzi and stopped to chat just as I fired it up, he felt the exhaust and suggested I check the valve clearance, can't check valves hot so on I went. Stopped for the night in Rushville, IL, checked valves Thursday morning, they were fine. Rode the rest of the way home and arrived last evening thinking all the way "What could be dumping raw fuel in the intake" came to the conclusion that I should look at the choke cable etc. for the right side. Bingo, got bike unloaded this morning, got tank off, (choke hidden under tank on that side), choke slide was stuck open by gritty stuff! I had that Tank off twice after the problem started and never checked the choke?????!!!!!!

Brian