TOPIC:

Hey friends, hoping you can help me out:

I drove from SF to lake tahoe yesterday. about 3000 feet the idle was dropping below 1000 so I turned the idle screw(throttle stop screw?) in. when I got up here the bike was coming down from revs really slow when I disengaged the clutch, I turned the idle back down and that seemed to help but now I'm not sure where the idle screw is in relation to sea level setting. This morning when I go to start it it'll fire(I can here the pops from combustion) but it won't start up completely. I'm guessing low oxygen at this altitude causing trouble? How can I play with it to get it started? Also running 93 octane which after research I think isn't good for high altitude?

Riding at high altitude and running 93 octane should cause no permanent changes in performance. It will run a bit rich at altitude because the air is thinner. 93 octane won't hurt anything, maybe a waste of money.

Assuming it's too rich to start , what direction do i turn the screw on the carb to adjust for that?

Run the lowest octane you can get for higher altitudes
More octane retards combustion and is good for higher compression engines and also helps with engine knock on hot days but in thinner air a lower octane ignites faster and gives you more power

Well, it's 3211 ft at my front door in Billings, and while I don't notice much change up to 5500 ft, when I ride to the top of Beartooth Pass, at 11,000 ft all my bikes have ben noticeably burbling -

Are your carbs / pipe / airbox stock ?

Yep, everything stock. My best guess is still running lean from 6000 ft elevation change. Carbs were balanced at sea level. I'm going to try adjusting the carbs but I left my service manual at home (doh!), which way do I turn the screw on each carb, and about how much?

Update: bumb started got it to run. It burbled as if it wasn't getting enough air and died on the first uphill. Just waiting on advice on how to richen up the mixture... ?

Edit:YouTube told me. Will try after lunch.

JohnB wrote: Update: bumb started got it to run. It burbled as if it wasn't getting enough air and died on the first uphill. Just waiting on advice on how to richen up the mixture... ?

Edit:YouTube told me. Will try after lunch.

If you are not getting enough air, you are already running TOO RICH.

On my carbs, the side screws rich up the pilot circuit by backing the screw on the side of the carb out, leaner by turning the screw in. This only adjusts the pilot jet circuit. You might need to adjust the main or needle if you are running that bad.

Pull your air filter and see if it runs. Had mine run badly once turned out the filter was toast. May be part of the problem, if nothing else it will tell if you are rich.

moneypit wrote: Pull your air filter and see if it runs. Had mine run badly once turned out the filter was toast. May be part of the problem, if nothing else it will tell if you are rich.

If the bike was tuned at sea level, and is now at 6000 feet above sea level, there is absolutely no doubt it's running rich. Less oxygen per cubic foot of air, and same amount of fuel equals "runs like crap".

I remember reading a Magazine road test of the new at the time 1980 KZ1000G with EFI. The testers were amazed because the bike didn't lose power at higher altitudes like all the carburated bikes did, because the EFI automatically compensated for density altitude.

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