How much advance on your 250?

[Bevel bob]

My 250 is in Mach1/ Mark111 tune, I know that other owners use between 32 and 40 degrees, i'm using 38, I suspect those using 32 are trying to give the big end an easy life, I think 40 would give more top end but my big end has done a big mileage so i'm being carefull till the next rebuild . What do you do?.

[JimF]

Hi Bob,

I have the Mach 1 at 8 degrees but it certainly must have the AAU unit behind the points.

My non-descript 250 with no AAU whatsoever is at 39 degrees.

Jim

[DewCatTea-Bob]

" I have the Mach 1 at 18 degrees but it certainly must have the AAU unit behind the points. "

____ A real Mach-I should gave it's static-advance set between only 8 to 12 degrees before TDC, NOT "18 degrees" !
Cuz in combo with it's stock 28-degree AAU, the 18-degrees static would make the total ign.advance TOO great (at 46-degrees BTDC) !
__ However if a 18-degree AAU is employed instead, then the resulting total ign.advance is okay,, but then that should mean that the Duke's ignition-system ought be as that of a Mark-III, and since that's the MAIN difference between a Mach-I & a Mark-III, THEN the Duke ought be referred to as a 'Mark-III' (rather than a "Mach 1") !


Dukaddy-DUKEs,
-Bob

[JimF]

Oops! my bad fingers - I have fixed my post.