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Author Topic: 069a carb screw replacements  (Read 942 times)

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Offline terryjennings

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069a carb screw replacements
« on: March 03, 2011, 09:15:22 AM »
I just got thru rebuilding a set of 059a Keihins on my '75 550. If you're looking for replacement stainless slide assy screws, top cover and float bowl socket head cap screws, go to Microfasteners.com. They have 3X10 button head socket screws for the slide assy and the 4mm and 5mm for the others. You have to order a minimum of 20 each for anything, but it's cheaper than anyone else wants for their kits. And, this is the only place I found the 3X10's for the slide.
Also, I found that the parts fische on bikebandit calls for 4X12 float bowl screws. These carbs actually use 4X10's if you don't use lock washers. The 12's will work, especially with washers, but they're longer than needed.
Hope this helps.

Offline lucky

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Re: 069a carb screw replacements
« Reply #1 on: August 24, 2011, 10:41:20 AM »
WARNING!!!!  Be VERY careful about replacing carb screws.

Look at them closely and you will notice that the head of most of the screws on the carb have a small punch mark. This is to identify them as ISO (International Standards Organization) metric threads. This was done starting around 1964 when there were many fires on motorcycles because people interchanged carb screws between IJS (international Japanese standard) and the ISO threaded carb screws.
The threads did not match and there were leaks. Remember There is the size if the screw and the PITCH of the metric screw. Like fine and coarse in SAE sizes.
http://www.newmotorcycleparts.com/fuel_system_parts/air_filters/pod_air_filters.html

See its not that you would probably mix up pre 1964 screws with modern ISO thread screws (it could happen), but you could go to a hardware store and get a metric screw that is 6mm but the thread pitch is wrong. Like 1.5 instead of 1.25 etc.,.

Make sure the pitch is a match.

If you walk into a motorcycle shop now days most mechanics do not know WHY that punch mark is on the screws on the carb. But I lived through the fires.
« Last Edit: August 24, 2011, 10:52:09 AM by lucky »

 

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