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Mikuni Carburetor Pilot Screw Cap Replacement

1
As can be seen in the photo, this is a bag of LED holders with rings. They are an essential component for the pilot screw replacement cap application but only the LED holders themselves will be necessary. If you're able to buy the holders seperately, do so. Otherwise simply discard the rings.

As can also be seen on the package, this set cost me CAD$1.50 but you may find what you need for less because this package contains enough holders for two sets of carburetors and also contains the unnecessary rings.

This sort of thing can be purchased in any electronics or electronics surplus store. Canadians can typically find LED holders at Radio Shack or Sayal Electronics and similar stores.
2
The LED holders you'll need are standard 5mm black. They have the perfect diameter to fit snuggly into the pilot screw holes of the Maxim-X Mikuni carburetors.

When the holders are in place, however, they themselves still need to be plugged to protect the pilot screws from debris and moisture.
3
To complete the replacement plug assembly, you'll need self-anchoring push-in fasteners like the ones in the adjacent picture. These fasteners are commonly used for automotive trim applications and are often referred to as Christmas Tree Fasteners.

The ones you'll need have these dimensions:
¼" Diameter x ½" Length

They can be purchased at automotive parts stores and through some specialty fastener suppliers. Canadians can find them near the Automotive Parts counter at any Canadian Tire store, part # 92-1692-6.

A set of four (4) fasteners will likely cost less than CAD$2.00 no matter where you find them.
4
Although the ¼" Christmas Tree fasteners have the right diameter for the application, their ½" length is almost twice what it should be.

To be certain that the fasteners seat on the LED holders and adequately seal the pilot screw holes, simply cut off approximately one third of the length of each fastener using side cutters or scissors as shown in the adjacent picture.
5
Most Maxim-X owners will be familiar with this sight - it's a view of a pilot screw hole on the top of a typical Maxim-X Mikuni carburetor.

At the factory, the hole is sealed by a plug, refered to by Yamaha as a CAP, Part #: 3F9-14118-00-00.

Unfortunately, the caps are usually destroyed when first removed and finding anything at all to replace them is difficult, if not impossible... until now.
6
Even if Yamaha could still supply the original caps, we all know they'd be priced too exhorbitently.

The alternative suggested here fits perfectly, is easy to find, easy to replace and costs very little.

Simply insert a standard 5mm black LED holder into each of the four pilot screw holes as shown in the adjacent picture.
7
Complete the replacement cap assembly by firmly pressing a shortened ¼" Christmas Tree fastener into each LED holder in each pilot screw hole as shown in the adjacent picture.

The completed plug assembly may not be 100% waterproof but it's definitely thoroughly water and dirt resistent. More importantly, the replacement plug assembly fits so snuggly that it won't fall out but it's also easily removable and reusable, unlike the original caps.

I've been searching for a replacement for years and this is definitely the answer. It's readily available, easy to assemble in a matter of minutes and costs less than CAD$5.00 to replace.