Free Seized Carb Screws

Introduction

Many people have difficulty when it comes to dismantling the carburettors - the screws often seem impossible to remove without stripping the heads. The problem stems from the fact that the screws holding together the carburettors are JIS screws (as denoted by the little dot on each head) and most people do not own a set of obscure JIS screwdrivers. Unlike a Phillips head, the JIS screws have parallel sides - the v-profile of a Phillips head screwdriver will simply cam out, stripping the head in the process.

Fortunately, there are a few solutions to removing stubborn screws. They have been laid out below in order of desperation - ie start at the top, and as it starts going wrong work your way to the bottom!

Extraction Methods

Pozidrive

A Pozidrive screwdriver has the parallel sides like the JIS head, but it also has small ridges that run in between each of the 4 slots which prevent a good fit. This can be overcome by seating the screwdriver in the screw head and then giving it a few firm hits with a hammer. Due to the soft nature of the screws this beds the screwdriver in for a much better fit and also loosens up the screw a little in the process. Make sure you apply lots of pressure onto the screw whilst you turn.

A #1 Pozidrive bit is the size to reach for.

Visegrips

Failing the #1 Pozidrive, it's time to move on to visegrips. This is an excellent solution once the head has been stripped. You will need grips that have serrations on the end where they will be gripping the screw head. Tighten the visegrips such that the jaws cut into the sides of the screw head and use the leverage of the grips to loosen the screw.

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Visegrips will work wonders on most screws, but a couple of them are hard/impossible to get to unless you have very fine nosed visegrips.

Screw Extractors

Got a set from the local HD that cost $20 but it can be found online for a few dollars cheaper. It made quick work of removing the stripped screws. Just make sure you keep both bowls on because there will be a lot of metal shavings. http://www.amazon.com/Alden-8430P-Grabit-Damaged-Extractor/dp/B000H6PM32/ref=sr_1_4?ie=UTF8&qid=1346922249&sr=8-4&keywords=alden+grabit

Dremel

The last port of call is the Dremel. Simply cut a slot across the head of the mashed screw with the cutting disc and turn with a large slotted screwdriver. Make sure you apply lots of pressure onto the screw whilst you turn.

Machine Shop

If it all goes belly up (which after all this is unlikely) take it to a machine shop and have them drill out the screw and tap it for the next size up.

Aftermath

After going to all the effort of removing these stubborn screws, save yourself the heartache in the future by replacing them with socket-head bolts! That way they can be easily undone with the appropriate allen key.

You will need:

  • 4 x M5x12mm (if you want to update the "vacuum caps" for shimming the needles with a washer or two)
  • 10 x M4x10mm (Plus a few more if you have the fancy factory emissions stuff on a newer bike)