Remove tricky studs

How to beat stubborn engine bolts, even if they’ve snapped

1

Get the right tool for the job

Studs are fasteners which are often used to secure components like exhaust headers or cylinder heads to the engine block itself. These will vary in size and quite often locate in hard-to-access places. It might seem logical to just pick up a set of grips, but trying to extract a stud using these isn’t the best course of action. So go bag yourself a stud extractor set for about £25.

3

Oh bugger, it’s snapped…

Despite using the correct tool the seemingly inevitable often happens. When a stud breaks off it usually does so flush with the surface. But if you’re lucky enough to be left with a good amount of thread exposed, say over 1cm, you can try using a set of mole grips to ease it out. Heat the area again and apply pressure with the mole grips both ways until it yields.

2

Pile on the pressure

Ideally with the component in a vice, select the correct sized extractor then apply even pressure using a ratchet to ease the stud out. If it refuses to budge use a heat gun to warm the surrounding area. This can often take a while because the heat is quickly dissipated through the rest of the part. The heat should ‘crack’ the bond between the steel stud and alloy body.

4

Using an ‘easy out kit’

If it’s snapped flush to the surface then you’ll need to extract it using an ‘easy out kit’. These kits have different sized extractor bits with left-hand threads which grip the stud harder as more force is applied. You’ll need to drill a small hole in the stud in order to insert the extractor, but first mark the centre of the stud precisely with a punch to help you drill it correctly.

5

Make some precision drilling

Drill a pilot hole using a 2mm bit. Be sure to invest in a good quality set of drill bits. The reality of low-quality items is that they cut really poorly and are prone to breaking, leaving half the bit buried in the hole, further adding to your woes. Drill to almost the bottom of the threads.

7

The right way is left

Use the largest sized extractor possible and drive it in with something that will apply force evenly – a tap driver is ideal. You need the extractor to go in as far as possible, remember they go in turning counterclockwise. It is this counter rotation that, as the extractor begins to bite into the drilled-out hole, produces the force to undo the bolt.

9

Fit the best bolts

Most modern bikes are fitted with metric fasteners, typically 6mm, 8mm and 10mm with a common thread pitch. This fact means that it’s possible to use pattern fasteners to replace lost or broken originals. But it’s worth bearing in mind that the quality of original parts is almost always superior to a generic pattern replacement and will be less prone to failure.

6

Turn up the heat

Drill into the pilot hole with a slightly bigger bit. The aim is to drill the bolt out to a size that gives the extractor the largest surface area to bite on to. Use a heat gun to warm the area around the seized bolt, this will expand the alloy and steel at different rates and help loosen the stud off.

8

Clean out the threads

With the broken stud removed it’s important to make sure the remaining threads are cleaned. Quite often the threads in the hole are contaminated by corrosion and all they need is cleaning out with a tap. Use a tap of the correct size to clean the threads out, ensuring any remaining swarf or gunge is cleaned out using an air line or contact cleaner.

10

Grease, lock and torque

When fitting your new bolt, be it good-quality pattern or an OE part, always use a smear of grease in order to prevent any further corrosion or seizing problems. Or, if there are specific instructions in the workshop manual to use a thread locking compound, do that instead – as well as tightening up to the correct specification using a torque wrench.