Well, I don't claim to be an expert either and I can't lay my hands on the
referance to the honing at the moment but the SU carbs are much higher
precision
that they might apear at first glance. I have mixed up a few dome/piston
sets. Usually it does not seem to make much differance. But, on some the piston
drop rate will be noticably different. Swap them back and they even up. I'm not
sure how it was done but you need to remember that labor in Japan was awfully
cheap in the '60s. With the large diameter of the piston and the low pressure
differentals the dome to piston clearance needs to be very close and
expecially consistant. The factory service manual is very specific about using
rags and
gasoline to clean them and to be very carefull to not scratch the surfaces.
keith
>
> Wait wait wait. I am NO expert on SU carbs (or much else for that matter),
> but I find it very hard to believe that each piston and dome were percision
> honed and matched as a set at the factory. It has been a while since I
>looked
> closely at an SU carb (I have SK sidedrafts) but as I recall they appear to
> be cast aluminum parts to me. I can imagine that there were specific
> tolerances and some final machining or clean up, but are you telling me that
>there
> was some guy at the factory that specifically matched each dome with each
> piston to the degree being suggested? And he would do this by...? He would
> check his work by...? To be sure of his work, I think it would have to be
>set up
> on some kind of airflow bench. Sounds VERY labor intensive to me. Unless
> you radically sanded the thing, I cannot imagine that the tolerances changed
> much. Again, please feel free to enlighten me. But for now, I suspect that
> something else is contributing to the differences you see in the ca!
> rbs.
> Ignorantly yours,
> Greg Burrows
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