High Speed stutter

[wiemer]

Agree with you Ed, it sounds like over-rich mixture.
I suppose that while giving much throttle (at reasonable RPM) the carbs open fully, independent of the mixture.

The opening depends solely on butterfly and RPM's (not quite: the depression before and after the slide)
I do not know at which RPM the carbs open fully, but my rough guess (judging after the intake noise- clam type box) is: well under 4000 RPM.


wiemer.

[steve hawkins]

My word it has been a while since I have been able to access this sight from my usual works computer.  

I am coming back from larger main jets to smaller ones as my plugs are well sooty.

I found one issue, that was limiting my top speed somewhat, and that was the fact that my exhaust valve clearances have closed up a bit.  Have to watch that one.  This has allowed me to go well beyond 90mph - ran out of road, the local 'drag strip' is only so long and there is the matter of other traffic!

I have moved the main jet back to standard for a 81 machine, although I do have carbs from a 79 (flat top),but I have the 81 heads.  The needle is still set in its highest position, so I will start moving that down to a more normal position, as I still have sooty plugs.  If I cannot rid myself of this flat spot, I will go leaner, I have the standard main jets for a 79 flat top.

Of course it could be that the carbs are shagged.....they have been rebuilt in the recent past and the diaphrams are fine.

Ho, hum,

Steve Hawkins