Timing and Altitude

I am at 6000 feet altitude.
What effect does altitude have on how the bike runs, other than too rich carburation?
Can,should, I advance the timing to crisp up the bike at this altitude?
I have a standard older boyer, I "think" the instructions said to set it at 32 degrees at full advance, is this correct? Maybe it was 28?
The bike "feels" somewhat "thudding", heavier if you will, loping around 3000rpm, and then runs better above about 3500.
Is this normal, any comments?

highdesert said:

I am at 6000 feet altitude.
What effect does altitude have on how the bike runs, other than too rich carburation?
Can,should, I advance the timing to crisp up the bike at this altitude?

Click to expand...

A Commando owner (MexicoMike) on the Britbike forum mentioned that he advanced his points ignition by 6 degrees (from 28 to 34 deg. BTDC) at 7,400ft which made: "a dramatic difference in acceleration over the stock setting".

highdesert said:

I have a standard older boyer, I "think" the instructions said to set it at 32 degrees at full advance, is this correct? Maybe it was 28?

Click to expand...

The standard ignition timing setting for a Boyer is 31 degrees at 5,000 RPM.: http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf

For altitude advance the timing about 3/4 degree for each 1000 feet above sea level. It will help a lot but will never get you bvack to sea level performance. Jim