TOPIC:

I have a US A3 (1981) and have just tried to remove the 'caps' over the idle mixture screws that are on the US models.  With respect to another member who explained his removal method, mine do not appear to be 'caps' at all and have verified from a previous post that I am in the right place.  I drilled into one 'cap' and found it to be perhaps 2 mm thick.  I have pried on it but it will not budge nor do I see a seam as if it is a part of the wall of the carb body.  I broke through and can see the brass mixture screw, but further drilling risks damaging the head of the screw so I have stopped the operation.

I would like to know what other members have done to get at this screw w/o damaging it.  Thanks.

can you get an old tap in far enough to enable you to pull the blanking plug out. Perhaps carefully drill the full diameter of the plug?

There are plugs there. The only way to get the brass pilot mixture screws in is from the top. All carburetors after 1972? had to have the idle mixture screws or in our case, the pilot mixture screws mechanically blocked so that non licensed individuals couldn't alter the factory setting of the mixture because of emissions standards.

I just pulled out my vernier caliper and measured up the bore that the plug sits in so that I can tell you what you're dealing with.
Bore diameter is .270" = 6.8mm
Bore depth is .100"  = 2.58 mm
The bore is necked down to  .200"  = 5.08mm



 

 

 

Chances are if you already have pilot holes (2mm?) in all 6 of the plugs and then  drill them SLOWLY with the 4mm drill bit, the bit will bite in to the plugs and spin them out all in one foul swoop. 

Okay, thanks guys.  At least now I know that I'm not crazy and I am definitely probing in the right place.  I may play around carefully with a drill today, or otherwise take Kawboy's numbers to the hardware store and search for a tap or tool so as to not damage the head of the screw.  Some of my cylinders are lean and I would like to take care of this problem properly with an adjustment or removal for proper cleaning.  

I'd like to know who is the BRAINIAC who mandated these caps.  I can't imagine that a few people enriching the mixture of a few LOW END jets on a few motorcycles can have any impact on pollution when those same bureaucrats fly private jets all over creation.

UPDATE: Success.  With surgical precision, I drilled tiny holes around the outside of the cap and removed it in pieces.  The caps are thicker than what I had imagined and I had wondered if I had been drilling into the wall of the carb somehow.  I now see that the cap and wall of the hole was lined with a very thin piece of plastic, but was probably corroded preventing it from more easily popping out.  Thanks again for those who responded which ensured me that I was headed in the right direction.

www.kz1300.com/index.php/forum/carburato...rb-rebuild-pt-1#5448